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The relationship between antigen structure and the requirement for the thymus cells in the immune response

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Abstract

Certain antigens such as polymerized flagellin are capable of producing relatively normal antibody levels in thymectomized mice, whereas others, including heterologous erythrocytes require the presence of T cells in a helper capacity. The mechanism of thymus-independent antibody production was investigated by comparing the primary IgM responses of spleen cells from ATXBM, XBM, and normal mice to various physical forms of the flagellar antigens of Salmonella adelaide in vitro. No reduction in antibody-forming cell levels to polymerized flagellin over a wide dose range was observed in ATXBM cultures, although the same spleen cells did not respond to an optimal dose of sheep red cells. In contrast, when flagellar determinants were presented in a monomeric form or as flagellin-coated donkey red cells, a highly significant difference was observed between the antibody responses of spleen cells from ATXBM mice and XBM or normal controls. The results suggested that the requirement for T cells in antibody production is not a property of specific antigenic determinants, but depends on the mode of antigenic presentation. The validity of this conclusion was confirmed by using another antigenic determinant (DNP) coupled either to the thymus-independent carrier, POL, or to the thymus-dependent carrier, DRC. Spleen cells from XBM mice produced comparable AFC levels to both forms of DNP, but the results from ATXBM cultures showed a marked difference. The anti-DNP response to DNP-DRC was greatly reduced compared to controls, whereas that to DNP-POL was normal even after prolonged thoracic duct drainage of the ATXBM donors and pretreatment of their spleen cells with anti-θ-serum and complement. The data presented here imply that the role of T cells in humoral immunity is the presentation of antigen to B cells in such a manner as to initiate optimal antibody synthesis.

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The induction of tolerance in guinea pigs with a 2,4-dinitrophenyl (DNP) derivative of a copolymer of copolymer of D-glutamic acid and D-lysine (D-GL) leads to a preferential depression of the capacity to produce high affinity anti-DNP antibody in response to immunization with DNP-guinea pig albumin. Thus, immunization 2 wk after tolerance induction with 3 mg of DNP-D-GL results in an immune response in which individual plaque-forming cells (PFC) secreting high affinity anti-DNP antibody are absent and in which the affinity of circulating anti-DNP antibody is reduced. A similar, but less marked, suppression is seen when 0.3 mg of DNP-D-GL is used for tolerance induction. If immunization is delayed until 2 months after tolerance induction, then suppression is restricted to the highest avidity PFC group. Our data is consistent with a state of tolerance in the pool of precursors of anti-DNP antibody-secreting cells induced as a result of their interaction with DNP-D-GL in the absence of specific "helper" cells, which appear to be lacking for DNP-D-GL. In such a situation, the affinity of receptors on precursor cells for tolerogen and the concentration of tolerogen appear to be crucial determinants of whether an individual cell will become tolerant.
Thesis
Epitope density appears to be a critical factor in pathogens that can elicit effective immune responses. All the viruses that have efficacious FDA-approved target vaccines have high surface densities of antigens. HIV, on the other hand, has a limited number of envelope glycoproteins present on individual virions on average, a characteristic with which HIV can evade from human immunity. To investigate how immune cells, particularly B cells, recognize and differentiate surface antigen density, we aim to build nanoparticles with different densities of antigens on the surface. Liposomes are chosen as antigen carriers for their clinical safety and engineering versatility. Both ensemble biochemistry assay and single-molecule biophysical techniques are developed to determine the spatial density of two model proteins on liposomal surface. Our results showed the initial density of protein conjugated on Ni-chelating liposomes could be finely controlled but decreased overtime. In comparison, maleimide-liposomes performed well in both protein density control and conjugation stability. Through maleimide-cysteine reaction, we successfully constructed liposomes with varied surface density levels of TNF-α peptide, a model self-antigen that is critical in the pathogenesis of rheumatoid arthritis. Immunization of mice using liposomes that display TNF-α peptide at high density consistently elicited both IgM and class-switched IgG antibodies that are reactive towards self-antigen TNF-α protein. In transgenic mice lacking either functional T-cell receptors or MHC II on B cells, the liposomal particles elicited similar levels of IgM and IgG responses, implying that this is a T-independent process. Addition of CpG or T-cell epitope tetanus toxin peptide improved antibody responses elicited by liposomal particles but not by soluble antigen peptide. Furthermore, the Ab titer elicited can be increased by 1000-fold upon replacement of liposomes by bacteriophage Qβ virus-like particles of similar epitope densities. Remarkably, this enhancement of Ab titer is almost lost entirely in transgenic mice lacking TCR or MHC II, which uncovers T cell help as the dominant mechanism behind this enhancement. In conclusion, high epitope density alone can trigger antibody class switching in B cells, and the cognate T-cell help recruited by components in VLPs can further boost antibody response by promoting affinity maturation. As an exploratory work to build on this mechanism of immunogenicity, we attempted next to build HIV VLP using the recombinant HIV Gag protein, which is known to contain many well-defined human T cell epitopes. If successful, the display of HIV envelope glycoproteins on the surface of this VLP at high density may afford an attractive lead for HIV vaccine development. HIV Gag protein can self-assemble in vitro to HIV virus-like particles, however, the quantitative aspects and in particular, the yield of this process are poorly characterized. Our results revealed that purified Gag proteins assembled into aggregates as large as micron-sized particles that are visible under light microscope. This self-assembly is induced by addition of nucleic acids and interestingly, it is reversible with the addition of excess nucleic acids. Thus, further engineering of this process is required in order to make it useful for production of HIV VLPs. In summary, our study overall has answered a fundamental question in immunology regarding B-cell activation by particulate antigens, offering insights into the process of pathogen recognition. These findings will help guide future design of therapeutic vaccines for chronic conditions including cancer and Alzheimer’s disease, as well as prophylactic vaccine for infectious agents like HIV.
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The binding of antigen to cells with antibody on their surface has been studied in a model system consisting of murine myeloma cells (MOPC 315) and DNP conjugates. Specific binding occurred between the DNP groups of DNP conjugates and cell surface immunoglobulin. Using this model, the binding affinities of multivalent and univalent DNP conjugates were measured directly by equilibrium-binding techniques and indirectly by displacement of bound conjugate with univalent hapten. With both approaches the multivalent conjugate was shown to bind to cells with an avidity 100–300 fold greater than the univalent hapten. Nonspecific binding of unrelated protein and repeated washing of cells was found to markedly dedecrease the specific binding of univalent conjugates, presumably because the relatively weak bonds dissociate readily.
Article
Mouse spleen cells capable of specifically binding intrinsically tritium-labeled polymerized flagellin (POL) (labeling by biosynthesis of flagellar protein) via IgM receptors were found to comprise a distinct population of about 20-50 cells per 10(6) lymphocytes. Evidence is presented that the majority of mouse spleen cells binding tritium-labeled POL undergoes blastogenesis after antigen capping, antigen shedding, and receptor reformation. Under conditions of tolerance induction in vitro, however, loss of antigen from the cell surface was inhibited. Such inhibition of antigen redistribution and shedding was reversed by a short pulse of colchicine and new antigen receptors were formed. In spite of this, colchicine had no effect on the tolerant state. However, tolerance could be broken, regardless of presence or absence of the alkaloid, with radioresistant theta-negative accessory (A) cells (adherent cells) from normal but not from tolerant spleen cell populations. "Tolerant" A cells, although they were incapable of cooperating in a response to POL, were capable of participating in a response to a second unrelated antigen. It is concluded that tolerance to POL in vitro is induced by mechanisms other than the physical blocking of bone marrow-derived (B) cell receptors by antigen. Most likely, the discrimination by the B cell between a tolerogenic and immunogenic signal is mediated by A cells.
Article
The experiments reported examined the fate and properties of antigen-binding B cells (ABC) during the induction of hapten-specific tolerance by 2,4-dinitrophenyl (DNP)-conjugated type 3 pneumococcal polysaccharide (S3). We found that (a) after short (nontolerogenic) pulses of DNP-S3, anti-DNP Ig receptors were physically blocked by cell-bound antigen. Removal of extracellular tolerogen led to full functional recovery of ABC. (b) After more prolonged (tolerogenic) exposures to DNP-S3 the degree of recovery of ABC following antigen-free culture was inversely related to the dose of antigen given, (c) Regardless of the dose or duration of exposure to DNP-S3, cells initially binding antigen effectively cleared it from their membranes; after tolerogenic exposures, cells neither carried cell-bound DNP-S3, nor expressed functional receptors, (d) Under conditions where tolerized cells recovered near normal levels of ABC after removal of extracellular antigen, these ABC appeared to display fewer receptors per cell than normal. We therefore propose that B cell inactivation by DNP-S3 involves the progressive and eventually irreversible inhibition of Ig receptor expression on DNP-reactive B cells, and is not due to stable blockade of receptors by cell-bound antigen. The relationship of this effect to other models of B cell inactivation (especially the similar phenomenon seen in immature B cells exposed to anti-receptor antisera) is discussed.
Article
The immunomodulating effects of staphylococcal enterotoxins on in vivo immune responses in C57BL/6 mice were examined. Of the five serological types A (SEA), B, C, D, and E (SEE), only SEA and SEE markedly suppressed the antibody response to sheep red blood cells (SRBC) when injected 1 day before or on the day of immunization with SRBC. Further study of SEA revealed that it did not affect the antibody response to a thymus-independent antigen, salmonella flagella, but did affect the T-cell-mediated immune response. Contact sensitivity to dinitrofluorobenzene (DNFB) was suppressed when SEA was injected before sensitization or before challenge with DNFB, indicating that SEA affected both the afferent and efferent phases of DNFB contact sensitivity. As the suppression of DNFB contact sensitivity could be transferred by anti-Thy-1.2 antibody-sensitive spleen cells of SEA injected donors into normal or DNFB-sensitized recipients, the suppression was thought to be an active one. However, SEA could augment the DNFB contact sensitivity when injected on the third day after sensitization with DNFB. These results indicate that the immunomodulating effects of SEA can be mediated by the T-cell function.
Article
A quantitative assay and characterization of oil-attached cell wall of Mycobacterium bovis BCG (BCG-CWS) which stimulates cell-mediated immunity of spleen cells to alloantigens in mice were carried out by an in vitro cell-mediated cytotoxicity test using 51Cr-labeled target cells. C57BL/6J mice (H-2b) were immunized intraperitoneally with mastocytoma cells (H-2d) with or without oil-attached BCG-CWS. The cytotoxicity, comparable to that of spleen cells from mice immunized with mastocytoma cells (3 × 107), could be induced in spleens of mice immunized with a mixture of mastocytoma cells (104) and oil-attached BCG-CWS. The enhancing effect persisted for 55 days or more after the alloantigenic immunization. Oil-attached BCG-CWS enhanced cell-mediated cytotoxicity of T cells in the spleen and the mesenteric lymph node, but not in the thymus. The cytotoxicity showed specificity toward the alloantigen used for immunization. In addition to BCG-CWS, the cell walls of Nocardia rubra and Corynebacterium diphtheriae PW8 and the peptidoglycolipids of Mycobacterium tuberculosis Aoyama B were found to be potent stimulants of cell-mediated cytotoxicity in mice. Oil-attached BCG-CWS did not enhance humoral response to mastocytoma cells but enhanced cell-mediated cytotoxicity when viable mastocytoma cells were used as antigen. The above result was supported by the fact that anti-hapten antibody response induced by viable trinitrophenyl (TNP)-mastocytoma cells (104) plus oil-attached BCG-CWS did not increase to the maximum level as was observed in mice immunized with a larger number of mastocytoma cells (3 × 107) alone, while cell-mediated cytotoxicity induced by the same treatment increased to the maximum level obtained by immunization with mastocytoma cells (3 × 107) alone.
Article
The periodic collagen-like polytripeptide (Pro-Gly-Pro)n is immunogenic in several species of animals. Antibodies to this polymer are specific to the unique collagen-like conformation of the immunogen. There is an immunological cross-reactivity between (Pro-Gly-Pro)n and natural collagens in several systems, and it is possible to induce an autoimmune response to collagen by means of the synthetic polymer. The ordered polymer (Pro-Gly-Pro)n as well as collagen are thymus-independent antigens, whereas the random polymer (Pro66, Gly34)n and gelatin are thymus dependent.
Article
Adjuvanticity of nystatin, one of the polyenic antifungal antibiotics having as its primary target the membrane sterol of eukaryotic cells, was investigated by examining its effect on several functions of mouse spleen cells relevant to immunological phenomena in vitro. Nystatin was found to stimulate significantly DNA synthesis in thymus-independent (B) cells but not in thymus-dependent (T) cells. Like the other B-cell mitogens such as bacterial lipopolysaccharide (LPS), nystatin elicited nonspecifically polyclonal antibody synthesis in mouse spleen cell cultures, and also restored antibody response of T cell-deficient spleen cells of congenitally athymic nude mice to heterologous erythrocytes (RBC; thymus-dependent antigen). Thus, nystatin and LPS appeared to cause similar changes in the functions of spleen cells relevant to immunological events. However, antagonism but no additive effect in the adjuvanticity was revealed between the two adjuvants. As an interesting finding, the polyclonal generation of anti-RBC antibody-forming cells (AFC) in the spleen cell cultures by stimulation with B-cell mitogen, i.e., either nystatin or LPS, was not inhibited at all by inclusion of any anti-RBC antiserum, whereas, as is well known, the generation of AFC by stimulation with the antigen was specifically suppressed by the corresponding antiserum, indicating a difference in the genesis between the mitogen-induced AFC and the antigen-induced AFC.
Article
The immune system is the responsible for body integrity and prevention of external invasion. On one side, nanoparticles are no triggers that the immune system is prepared to detect, on the other side it is known that foreign bodies, not only bacteria, viruses and parasites, but also inorganic matter, can cause various pathologies such as silicosis, asbestosis or inflammatory reactions. Therefore, nanoparticles entering the body, after interaction with proteins, will be either recognized as self-agents or detected by the immune system, encompassing immunostimulation or immunosuppression responses. The nature of these interactions seems to be dictated not specially by the composition of the material but by modifications of NP coating (composition, surface charge and structure). Herein, we explore the use of gold nanoparticles as substrates to carry multifunctional ligands to manipulate the immune system in a controlled manner, from undetection to immunostimulation. Murine bone marrow macrophages can be activated with artificial nanometric objects consisting of a gold nanoparticle functionalized with peptides. In the presence of some conjugates, macrophage proliferation was stopped and pro-inflammatory cytokines were induced. The biochemical type of response depended on the type of conjugated peptide and was correlated with the degree of ordering in the peptide coating. These findings help to illustrate the basic requirements involved in medical NP conjugate design to either activate the immune system or hide from it, in order to reach their targets before being removed by phagocytes. Additionally, it opens up the possibility to modulate the immune response in order to suppress unwanted responses resulting from autoimmunity, or allergy or to stimulate protective responses against pathogens.
Article
Antibody responses against antibodies, such as rheumatoid factors, are found in several immunopathological diseases and may play a role in disease pathogenesis. Experience shows that they are usually difficult to induce experimentally. Antibodies specific for immunoglobulin constant regions (anti-allotypic) or for variable regions (anti-idiotypic) have been investigated in animal models; the latter have even been postulated to regulate antibody and T cell responses via network-like interactions. Why and how such anti-antibodies are induced during autoimmune diseases, has remained largely unclear. Because repetitively arranged epitopes in a paracrystalline structure of a viral envelope cross-link B cell receptors efficiently to induce a prompt T-independent IgM response, this study used immune complexes containing viruses or bacteria to evaluate the role of antigen pattern for induction of anti-antibody responses. We present evidence that antibodies bound to strictly ordered, but not to irregularly arranged, antigens dramatically enhance induction of anti-antibodies, already after a single immunization and without using adjuvants. The results indicate a novel link between anti-antibody responses and infectious agents, and suggest a similar role for repetitive self-antigens such as DNA or collagen involved in chronic immunopathological diseases.
Article
Medicago, Inc. has developed an efficient virus-like particle (VLP) vaccine production platform using the Nicotiana benthamiana expression system, and currently has influenza-based products targeting seasonal/pandemic hemagglutinin (HA) proteins in advanced clinical trials. We wished to generate a trackable HA-based VLP that would allow us to study both particle assembly in plants and VLP interactions within the mammalian immune system. To this end, a fusion protein was designed, composed of H5 (from influenza A/Indonesia/05/2005 [H5N1]) with enhanced green fluorescent protein (eGFP). Expression of H5-eGFP in N. benthamiana produced brightly fluorescent ∼160 nm particles resembling H5-VLPs. H5-eGFP-VLPs elicited anti-H5 serologic responses in mice comparable to those elicited by H5-VLPs in almost all assays tested (hemagglutination inhibition/IgG(total)/IgG1/IgG2b/IgG2a:IgG1 ratio), as well as a superior anti-GFP IgG response (mean optical density = 2.52 ± 0.16 sem) to that elicited by soluble GFP (mean optical density = 0.12 ± 0.06 sem). Confocal imaging of N. benthamiana cells expressing H5-eGFP displayed large fluorescent accumulations at the cell periphery, and draining lymph nodes from mice given H5-eGFP-VLPs via footpad injection demonstrated bright fluorescence shortly after administration (10 min), providing proof of concept that the H5-eGFP-protein/VLPs could be used to monitor both VLP assembly and immune trafficking. Given these findings, this novel fluorescent reagent will be a powerful tool to gain further fundamental insight into the biology of influenza VLP vaccines.-Young, K. R., Arthus-Cartier, G., Yam, K. K., Lavoie, P.-O., Landry, N., D'Aoust, M.-A., Vézina, L.-P., Couture, M. M.-J., Ward, B. J. Generation and characterization of a trackable plant-made influenza H5 virus-like particle (VLP) containing enhanced green fluorescent protein (eGFP). © FASEB.
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Antibody production to type III pneumococcal polysaccharide (SIII) is not reduced in mice deprived of T cells (1). The properties of the antigen which enable it to trigger a “thymus-independent” B cell response are not understood but several unusual features can be listed. SIII contains few antigenic determinants, it persists in vivo for long periods of time, and can “neutralize” circulating anti-SIII antibody. Macroglobulin is the predominant antibody elicited by purified SIII in mice although immunization with the whole pneumococcal organism in various species results in 7S anti-SIII antibody. There is no evidence in any species that the purified antigen induces T cells to perform helper functions in antibody production, to elicit delayed hypersensitivity reactions, or to proliferate in vitro in response to the antigen (2 and 3 for recent reviews). The inability of SIII to engage T cells in immune responses may reflect an absence, or functional lack of expression, of V genes in T cells coding for the limited number of determinants on SIII or may reflect an extreme sensitivity of reactive T cells to tolerance induction by SIII.
Article
Human viruses possess very complex supramolecular structures. Both icosahedral and enveloped viruses typically display an array of viral-encoded protein antigens at varied spatial densities on the viral particle surface. The viral nucleic acid genome, on the other hand, is encapsulated inside the viral particle. Although both the surface antigen and the interior nucleic acids could independently produce immunological responses, how B cells integrate these two types of signals and respond to a typical virus particle to initiate activation is not well understood at a molecular level. The study of these fundamental biological processes would benefit from the development of viral structural mimics that are well constructed to incorporate both quantitative and qualitative viral features for presentation to B cells. These novel tools would enable researchers to systematically dissect the underlying processes. Here we report the development of such particulate antigens based on liposomes engineered to display a model protein antigen, hen egg lysozyme (HEL). We developed methods to overexpress and purify various affinity mutants of HEL from E. coli. We conjugated the purified recombinant HEL proteins onto the surface of a virion-sized liposome in an orientation-specific manner at defined spatial densities, and also encapsulated nucleic acid molecules into the interior of the liposome. Both the chemical conjugation of the HEL antigen on liposome surfaces and the encapsulation of nucleic acids were stable under physiologically relevant conditions. These liposomes elicited antigen-specific B cell responses in vitro, which validate these supramolecular structures as a novel and effective approach to mimic and systematically isolate the role of essential viral features in directing the B cell response to particulate antigens.
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The number and spacing of B-cell epitopes on antigens have a profound impact on the activation of B cells and elicitation of antibody responses, the quantitative aspects of which may be utilized for rational design of vaccines. Ni-chelating liposomes have been widely used as protein carriers in experimental studies of vaccine delivery, owing to the convenience and versatility of this conjugation chemistry. However, the epitope number per particle as well as the stability of protein conjugation on liposomes remain far less characterized. Here we have developed quantitative methods to measure the average spatial density of proteins on liposomes using both ensemble and single-molecule techniques and demonstrated their utility using liposomes conjugated with native proteins of two different sizes. These studies revealed that the initial density of protein conjugation on Ni-chelating liposomes can be fine controlled, but the density can decrease over time upon dilution due to the noncovalent nature of Ni-chelation chemistry. These results indicate that alternative method other than the Ni-chelation chemistry is needed for stable conjugation of epitopes onto liposomes and also suggest a general strategy that can be used to precisely regulate the epitope density on liposomes for B-cell antigen delivery.
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“Suppressor Cells: Permitters and Promoters of Malignancy?” was the title of a review article published by one of us in 1979 (1). This paper focused on the interrelationships between a neoplasm and the cells regulating the immune system. Unfortunately, the question mark, which was an integral part of the title six years ago, cannot yet be replaced by an exclamation mark, because the mechanisms controlling tumor growth are still unclear. However, the intriguing hypothesis that suppressor cells support tumor growth, and that their elimination may encourage tumor rejection still occupies the imagination of many tumor immunologists who are using a variety of experimental model systems, both in animals and in humans, in order to test the above prediction.
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From the clinician’s point of view, the wider use of transplantation as a remedy for disease is being restrained by a number of factors. Despite the considerable degree of success achieved in its most extensive clinical application — kidney transplantation — transplantation of organs must still be regarded as an experimental procedure (Hume, 1971). The central stumbling block is the rejection, since due to an apparently immutable law of immunity the transplantation of tissues to a genetically, i.e. antigenically dissimilar host inevitably mobilizes defense mechanisms against the foreign antigens. It has been suggested that this law may have a crucial loophole. The canine and, particularly, the porcine liver appear to be immunologically favored, since in unmodified hosts identifiable allograft rejection did not occur or reversed spontaneously, whereas in the same animals skin and kidney were regularly rejected (Calne et al., 1969; Garnier et al., 1970). In human liver transplantation it has become the usual practice to ignore the result of HL-A typing (Starzl, 1971; Calne, 1974). Since other experimenters found that canine, porcine, and rat liver allografts were rejected in the usual way (Porter, 1969; Jerusalem et al., 1971b; Jap, 1971), the above findings may represent a particular modification of the immunologic network of responses, rather than an exception to the principle of the transplantation reaction.
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Foot-and mouth disease virus is a highly contagious viral disease. Antibodies are pivotal in providing protection against FMDV infection. Serological protection against one FMDV serotype doesn't confer inter-serotypic protection. However, some historical data have shown inter-serotypic protection can be induced following sequential FMDV challenge with multiple FMDV serotypes. In this study we have investigated the kinetics of the FMDV-specific antibody secreting cell response following homologous and heterologous inactivated FMDV vaccination regimes. We have demonstrated that the kinetics of the B cell response are similar between all four FMDV serotypes tested following a homologous FMDV vaccination regime. When a heterologous vaccination regime was used with the sequential inoculation of three different inactivated FMDV serotypes (O-, A- and Asia1-serotypes) a B cell response to FMDV SAT1 and C-serotype was induced. The studies also revealed that the local lymphoid tissue had detectable FMDV-specific antibody secreting cells (ASCs) in the absence of circulating FMDV-specific ASCs indicating the presence of short-lived ASCs; a hallmark of a T-independent 2 (TI-2) antigenic response to inactivated FMDV capsid. Importance • Development of intra-serotypic response following a sequential vaccination regime of four different FMDV serotypes. • Indication of short-lived ASCs in the local lymphoid tissue — further evidence of a TI-2 type response to FMDV.
Article
Anti-TNF Therapy, Page 1 of 2 Abstract Tumor necrosis factor (TNF) is one of the most important cytokines produced by macrophages. TNF is a very important component of host defense, released very rapidly after all types of injuries and stimuli. The kinetics of TNF release are short, and so it is perhaps not surprising that prolonged TNF production is associated with pathology. This was first elucidated in rheumatoid arthritis but extends to other chronic inflammatory diseases such as Crohn’s disease and psoriasis. In this chapter, the discovery of anti-TNF therapy is reviewed, with its benefit but also its limitations. The potential of anti-TNF therapy in other diseases, e.g., cardiovascular and fibrosis, is discussed, as is the opportunity to define ways of blocking TNF synthesis.
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From an academic viewpoint, two important questions facing immunologists are: 1. Are immunocompetent lymphocytes so restricted that individual cells have on their surface immunoglobulin (Ig) receptors of a single specificity (amino acid sequence) as far as the binding site for antigen is concerned? 2. If so, how is this situation achieved; i.e. how is the diversity generated?
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Caulobacters are often cited as examples of the diverse group of microorganisms categorized as the prosthecate bacteria; bacteria that produce appendages that are an extension of the cell membrane and wall. As is true for other prosthecate bacteria, caulobacters are found widely in the open environment, inhabiting lakes, streams, soils and the oceans (Poindexter, 1981). Because of their abundance or at least frequent appearance in locales with limited amounts of available nutrients, they are often used as the example of an oligotrophic bacterium.
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Experiments were designed to test the possibility that thymus-derived (T) cells cooperate with nonthymus derived (B) cells in antibody responses by acting as passive carriers of antigen. Thoracic duct lymphocytes (TDL) from fowl γG-tolerant mice were incubated in vitro with fowl anti-mouse lymphocyte globulin (FALG), which was shown not to be immunosuppressive in mice. On transfer into adult thymectomized, irradiated, and marrow protected (TxBM) hosts together with a control antigen, horse RBC, a response to horse RBC but not to fowl γG was obtained. By contrast, TxBM recipients of nontolerant, FALG-coated TDL responded to both antigens and the antibody-forming cells were shown to be derived from the host, not from the injected TDL. These findings suggested that, under the conditions of the experiment, triggering of unprimed B cells in the spleens of TxBM hosts was not achieved with antigen-coated tolerant lymphocytes. Another model utilized the ability of B cells to bind antibody-antigen complexes. Spleen cells from TxBM mice, incubated in vitro with anti-fowl γG-fowl γG·NIP, were injected with or without normal TDL (a source of T cells) into irradiated hosts. Only mice given both cell types could produce an anti-NIP antibody response. In a further experiment, spleen cells from HGG·NIP-primed mice were injected together with NIP-coated B cells (prepared as above) into irradiated hosts. A substantial anti-NIP antibody response occurred. If, however, the T cells in the spleens of HGG·NIP-primed mice were eliminated by treatment with anti-θ serum and complement, the NIP response was abolished. It was concluded that antigen-coated B cells could not substitute for T cells either in the primary or secondary response. Treatment of T cells from unprimed or primed mice with mitomycin C impaired their capacity to collaborate with B cells on transfer into irradiated hosts. Taken together these findings suggest that before collaboration can take place T cells must be activated by antigen to differentiate and in so doing may produce some factor essential for triggering of B cells.
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Only a brief summary will be given of the present concepts concerning these subjects.
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Vertebrate collagen (Fig. IB) is made up of three polypetide chains (designated α-chains), each of about 1000 amino acid residues and having a molecular weight of about 95,000. Each chain is coiled in a left-handed helix, and the three chains are coiled in a right-handed superhelix. The triple-stranded, coiled-coil structure is rod shaped, having the dimensions of 3000 x 15 Å. Chemical studies established that the three component polypeptide chains extend in parallel the full length of the molecule.
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Immunologists strive to understand the mechanism by which lymphoid cells are stimulated by antigen to produce antibody. One approach to this problem is the identification of particularly immunogenic molecules. By comparing the structures of immunogenic and nonimmunogenic molecules possessing the same antigenic determinants, some of the details of the “key” which turns lymphocytes on should be revealed.
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The purpose of this chapter is to present an integrated view of the various serological techniques that have been used in virology. The accent will be placed on the principles that govern each type of test and on the general applicability of the different serological techniques in all fields of virus research. In recent years, advances in serological techniques have sometimes been applied in only one area of virology, although they could have been equally useful to workers studying other groups of viruses. No doubt this stems from the host-oriented approach that has guided the compartmentation of virology into separate fields of specialization. When it comes to serological properties, however, the similarities between animal, insect, bacterial, and plant viruses are paramount. The same immunochemical principles govern the in vitro serological reactions of all viral antigens, and much of general interest can be learned from the findings obtained with each particular group of viruses. An attempt will be made here to emphasize the general validity of specific experimental procedures.
Article
The role of T* cells in the immune response of a given individual will depend significantly on the nature of the specific antigen tested. Furthermore, the immune response to many antigens may vary markedly from individual to individual, immediately raising the questions—of to what degree might the functions of immunocompetent cells (including T cells) be host dependent and what mechanisms might control this host variation. The availability of antigens of restricted heterogeneity and highly inbred strains of animals has enabled investigators during the past decade to design studies to answer these questions. Emerging from these studies is a growing body of evidence documenting and clarifying the role of genetic factors in determining the variability and patterns of immune responses in different hosts.
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During the past decade, the concept of antibody affinity has been increasingly employed in the analysis of immunological phenomena, and it is now generally understood to be an essential element in developing molecular interpretations of immunological processes. Consequently, there has been increased attention to a number of distinctive features of antibody affinity, particularly its variability and regulation, the role of antibody multivalence, and the biological concomitants of these properties. In an earlier discussion of the affinity of antibody (Karush, 1962), the main emphasis was placed on the nature and quantitative significance of the intermolecular forces involved and on some thermodynamic aspects of the reversible reaction of antibody and ligand. This analysis differs in its focus because it is based on experimental studies concerned with the variability of affinity (“the maturation process”) as well as the range of affinity, the kinetic features of the rapid antibody-ligand interaction, and the contribution of multivalence to the effective affinity of the antibody molecule. The information now available in these areas stems from the introduction of new experimental methods into immunological research. These methods include (1) the techniques of stop-flow and temperature jump for evaluating the kinetic parameters of the formation of antibody-ligand complexes; (2) the inhibition of hemolytic plaques, formed by suspensions of antibody-secreting cells, by soluble ligands to estimate relative affinities; and (3) the neutralization of hapten-conjugated bacteriophage with antihapten antibody to measure rates of binding of antibody to large ligands and to evaluate the quantitative effects of multivalent interaction.
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An injection of viable thymus or thoracic duct lymphocytes was absolutely essential to enable a normal or near-normal 19S liemolysin-forming cell response in the spleens of neonatally thymectomized mice challenged with sheep erythrocytes. Syngeneic thymus lymphocytes were as effective as thoracic duct lymphocytes in this system and allogeneic or semiallogeneic cells could also reconstitute their hosts. No significant elevation of the response was achieved by giving either bone marrow cells, irradiated thymus or thoracic duct cells, thymus extracts or yeast. Spleen cells from reconstituted mice were exposed to anti-H2 sera directed against either the donor of the thymus or thoracic duct cells, or against the neonatally thymectomized host. Only isoantisera directed against the host could significantly reduce the number of hemolysin-forming cells present in the spleen cell suspensions. It is concluded that these antibody-forming cells are derived, not from the inoculated thymus or thoracic duct lymphocytes, but from the host. Thoracic duct cells from donors specifically immunologically tolerant of sheep erythrocytes had a markedly reduced restorative capacity in neonatally thymectomized recipients challenged with sheep erythrocytes. These results have suggested that there are cell types, in thymus or thoracic duct lymph, with capacities to react specifically with antigen and to induce the differentiation, to antibody-forming cells, of hemolysin-forming cell precursors derived from a separate cell line present in the neonatally thymectomized hosts.
Article
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An injection of viable thymus or thoracic duct lymphocytes was absolutely essential to enable a normal or near-normal 19S liemolysin-forming cell response in the spleens of neonatally thymectomized mice challenged with sheep erythrocytes. Syngeneic thymus lymphocytes were as effective as thoracic duct lymphocytes in this system and allogeneic or semiallogeneic cells could also reconstitute their hosts. No significant elevation of the response was achieved by giving either bone marrow cells, irradiated thymus or thoracic duct cells, thymus extracts or yeast. Spleen cells from reconstituted mice were exposed to anti-H2 sera directed against either the donor of the thymus or thoracic duct cells, or against the neonatally thymectomized host. Only isoantisera directed against the host could significantly reduce the number of hemolysin-forming cells present in the spleen cell suspensions. It is concluded that these antibody-forming cells are derived, not from the inoculated thymus or thoracic duct lymphocytes, but from the host. Thoracic duct cells from donors specifically immunologically tolerant of sheep erythrocytes had a markedly reduced restorative capacity in neonatally thymectomized recipients challenged with sheep erythrocytes. These results have suggested that there are cell types, in thymus or thoracic duct lymph, with capacities to react specifically with antigen and to induce the differentiation, to antibody-forming cells, of hemolysin-forming cell precursors derived from a separate cell line present in the neonatally thymectomized hosts.
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The BJC is owned by Cancer Research UK, a charity dedicated to understanding the causes, prevention and treatment of cancer and to making sure that the best new treatments reach patients in the clinic as quickly as possible. The journal reflects these aims. It was founded more than fifty years ago and, from the start, its far-sighted mission was to encourage communication of the very best cancer research from laboratories and clinics in all countries. The breadth of its coverage, its editorial independence and it consistent high standards, have made BJC one of the world's premier general cancer journals. Its increasing popularity is reflected by a steadily rising impact factor.
Article
Immunological tolerance to H antigens of Salmonella adelaide may be induced in vitro by the exposure of mouse spleen cells for 6 hr to an immunogenic dose of polymerized flagellin in the presence of low concentrations of specific antibody. Such antibody-mediated tolerance requires an optimal antigen: antibody ratio for its induction. A shift in this ratio in favor of the antibody concentration results in failure of tolerance induction and leads to immune suppression commonly known as antibody-mediated feedback inhibition which is not analogous to immunological tolerance. Fragment A of flagellin fails to induce immunological tolerance in vitro. Tolerance to polymerized flagellin may however be induced in vitro, provided the spleen cells are exposed to fragment A in the presence of specific antibody for 6 hr. The results are discussed in the light of current theories of the mechanism of tolerance induction.
Article
Transfer of live lymphoid cells from BGG-immunized strain 2 guinea pigs into syngeneic animals primed with DNP-OVA prepares the recipients for a markedly enhanced secondary anti-DNP antibody response upon challenge with DNP-BGG. This phenomenon has been demonstrated when the recipients were challenged 1 day after cell transfer, but it was considerably more striking when an interval of 6 days was allowed between transfer of cells and challenge with antigen. As demonstrated in the preceding paper (6), BGG preimmunization enhanced anti-DNP antibody responses to challenge with DNP-BGG. An analysis of the characteristics of substances to which preimmunization was effective in enhancing subsequent anti-hapten responses was made. It was shown that preimmunization of strain 13 guinea pigs with a copolymer of glutamic acid and lysine (GL), to which these animals are genetically unable to accord an immune response, failed to prepare them for an enhanced anti-DNP response to DNP-GL. Tolerance to BGG specifically abrogated the capacity of subsequent BGG immunization to prepare DNP-OVA primed rabbits for an enhanced anti-DNP response to DNP-BGG. Sensitization of animals to haptens by preimmunization with hapten-protein conjugates failed to prepare them for enhanced primary or secondary antibody responses to other determinants associated with that hapten on a different carrier. These studies indicate that the enhancing effect of carrier preimmunization reflects a cooperative interaction between lymphoid cells specific for carrier and cells specialized for haptenic determinants. Furthermore, the capacity of a substance to behave as a carrier requires more than its possession of a variety of antigenic determinants.
Article
Transfer of live lymphoid cells from BGG-immunized strain 2 guinea pigs into syngeneic animals primed with DNP-OVA prepares the recipients for a markedly enhanced secondary anti-DNP antibody response upon challenge with DNP-BGG. This phenomenon has been demonstrated when the recipients were challenged 1 day after cell transfer, but it was considerably more striking when an interval of 6 days was allowed between transfer of cells and challenge with antigen. As demonstrated in the preceding paper (6), BGG preimmunization enhanced anti-DNP antibody responses to challenge with DNP-BGG. An analysis of the characteristics of substances to which preimmunization was effective in enhancing subsequent anti-hapten responses was made. It was shown that preimmunization of strain 13 guinea pigs with a copolymer of glutamic acid and lysine (GL), to which these animals are genetically unable to accord an immune response, failed to prepare them for an enhanced anti-DNP response to DNP-GL. Tolerance to BGG specifically abrogated the capacity of subsequent BGG immunization to prepare DNP-OVA primed rabbits for an enhanced anti-DNP response to DNP-BGG. Sensitization of animals to haptens by preimmunization with hapten-protein conjugates failed to prepare them for enhanced primary or secondary antibody responses to other determinants associated with that hapten on a different carrier. These studies indicate that the enhancing effect of carrier preimmunization reflects a cooperative interaction between lymphoid cells specific for carrier and cells specialized for haptenic determinants. Furthermore, the capacity of a substance to behave as a carrier requires more than its possession of a variety of antigenic determinants.
Article
Preimmunization of either guinea pigs or rabbits to bovine gamma globulin (BGG) prepares the animals for markedly enhanced antibody responses to 2,4-dinitrophenyl-BGG (DNP-BGG). This phenomenon is observed both in the primary anti-DNP antibody response to DNP-BGG and in the secondary anti-DNP antibody response to DNP-BGG in animals primed with DNP-ovalbumin (DNP-OVA). The BGG preimmunization is most effective if the antigen is administered as a complete Freund's adjuvant emulsion; in rabbits, a dose of 1 microg of BGG is more effective than a dose of 50 microg, whereas the reverse is true in guinea pigs. Transfusion of homologous anti-BGG sera fails to replace active immunization with BGG in the preparation of animals for these enhanced anti-DNP antibody responses. Both the immunoglobulin class and the average association constant for epsilon-DNP-L-lysine of the anti-DNP antibody produced in these enhanced responses is determined by the mode and time of immunization with haptenic conjugates and is not appreciably influenced by the nature of the carrier preimmunization. These studies indicate that the carrier specificity of hapten-specific anamnestic antibody responses is largely due to the interaction of two independent cell associated recognition units, one specialized for carrier and the other specific for haptenic determinants.
Article
Table 1 Primary Immune Response to DNP-POL in vitroAntigenNil3 ? 106 SRC100 ng DNP-POL100 ng POLSRCImmune response (AFC/culture-SRC-DNP-mean and range)"DNP"210 (90-525) 2,850 (1,200-6,200) 220 (90-560) 260 (70-460)190 (100-480) 2,750 (1,100-6,450) 1,100 (500-3,100)240 (9^480)Nil Nil 1,030(400-2,500)NilThese results represent twelve consecutive in vitro experiments with DNP-POL, in which 1.5 ?
Article
The response to two bacterial antigens has been studied in the lymph nodes draining their site of injection in normal mice, and in thymectomized, irradiated bone-marrow injected mice with and without a reconstituting thymus graft. A chromosome marker was used to differentiate between the response of cells derived from the bone-marrow and the thymus graft. Cells of thymic origin were stimulated to mitosis only to a slight extent by salmonellar flagella and not at all by pneumococcal polysaccharide. Histopathological changes in the regional lymph nodes were small compared with those previously studied (to sheep red blood cells and to oxazolone). Animals deficient in thymus cells were incapable of sustained antibody production after injection of salmonellar flagella but they were able to produce nearly normal amounts of circulating antibody against pneumococcal polysaccharide.
Article
A new method is described for the enumeration of single cells producing antibody against a pure protein preparation from Salmonella adelaide flagella. Cells with adherent bacteria, cultured in nutrient agar, give rise to bacteria adherence colonies which can be counted under low power magnification. The method discloses an extremely low level of background of 0.03 adherence colonies/106 spleen cells. Critical tests have affirmed that adherence colonies are due to cells actually taking part in the immune response. Since the method is based on an antigen known to be highly immunogenic and capable of evoking secondary responses as well as tolerance under defined circumstances, all major phenomena of immunity can be studied at the cellular level.
Article
THE localized haemolysis-in-gel (LHG) assay1, originally applied to the detection and enumeration of cells producing antibodies to erythrocyte cell wall antigens, has been extended to the detection of cells forming antibodies to hapten2-7 and protein antigens8,9. In these experiments the antigens or haptens were bound to the erythrocyte by direct chemical reaction. From our experience, and that of others, the main drawbacks of such a chemical approach for the attachment of ligands to a living cell are as follows: (1) direct chemical modification of the erythrocyte causes damage to the cell membrane resulting in cellular fragility and tendency to haemolyse6; (2) because crythrocytes must be sensitized anew each day, fresh reagents and large amounts of materials (in the case of protein antigens) are required on each day of the experiment4,8; (3) the extent of modification may vary between preparations, and the degree of substitution is difficult to measure, resulting in irreproducibility of results.
Article
MOUSE thymus cells possess a high concentration of the theta (theta)1 and Ly2 antigens. Several approaches have demonstrated that the sensitivity of peripheral muriiie lymphocytes to the cytotoxic effect of theta and Ly antibodies is a thymus-dependent property. The population of cells sensitive to the cytotoxic effect of theta antibodies disappears from lymph nodes3 and spleen4 after neonatal thymectomy. Similarly, following neonatal thymectomy, the population of cells sensitive to Ly antibodies disappears from lymph nodes (unpublished results of M. S. and Yron). Following administration of heterologous anti-lymphocyte serum, a procedure resulting in elimination of thymus-dependent lymphocytes5,6, cells sensitive to theta antibodies disappear transiently from the lymph nodes7 and spleen4.
Article
THE immune response involves the appearance of anti-body secreting cells as well as antigen binding cells. Antibody secreting cells can be counted in vitro using-Jerne and Nordin's local haemolysis in gel (LHG) assay1, and are then called plaque forming cells (PFC). Antigen binding cells can be recognized by their ability to bind particulate antigens such as sheep red cells (SRB) to their surfaces and have been named rosette forming cells (RFC)2,3. It is likely that RFC represent a mixture of antibody secreting cells and non-antibody secreting cells. Howard et al.4 studied the RFC response in the spleens of mice tolerant to pneumococcal polysaccharide. Although serum antibodies could not be seen in these animals a considerable number, larger, in fact, in ``tolerant'' than in optimally immunized animals, of RFC was found. They explained these findings on the basis that antibody secreting cells existed but that the humoral antibodies produced were neutralized extra-cellularly by persisting undegraded antigen.
Article
Immunological tolerance to H antigens of Salmonella adelaide may be induced in vitro by the exposure of mouse spleen cells for 6 hr to an immunogenic dose of polymerized flagellin in the presence of low concentrations of specific antibody. Such antibody-mediated tolerance requires an optimal antigen: antibody ratio for its induction. A shift in this ratio in favor of the antibody concentration results in failure of tolerance induction and leads to immune suppression commonly known as antibody-mediated feedback inhibition which is not analogous to immunological tolerance. Fragment A of flagellin fails to induce immunological tolerance in vitro. Tolerance to polymerized flagellin may however be induced in vitro, provided the spleen cells are exposed to fragment A in the presence of specific antibody for 6 hr. The results are discussed in the light of current theories of the mechanism of tolerance induction.
Article
THE usefulness of the theta (theta) alloantigen as a marker for thymus-derived lymphocytes in mice1-6 has emphasized the need for a distinguishing marker for thymus-independent (bone marrow-derived) lymphocytes, about which relatively little is known. We have raised an antiserum in a rabbit against lymph node cells from mice which had been thymectomized, irradiated and reconstituted with foetal liver cells, which after appropriate absorption was cytotoxic only to those lymphoid cells which were thymus-independent. Because the cell surface antigen(s) with which the antiserum is principally reacting seems to be species-specific, we have followed the example of Shigeno et al.7 and have called it MBLA (mouse-specific bone marrow-derived lymphocyte antigen).
Article
THERE is a relationship between the thymus and the pool of recirculating small lymphocytes. The immune defects of neonatally thymectomized mice are associated with a marked diminution of recirculating lymphocytes, as measured by the number of cells that can be obtained by prolonged thoracic duct drainage1, and with a severe cellular depletion in the “thymus-dependent” areas of the lymphoid tissues-in the periarteriolar lymphocyte sheaths of the spleen and paracortical areas of the lymph nodes23, for example-in general in those regions known to be the sites of extensive traffic of small lymphocytes4.The deficiencies of thymectomized mice can be reversed, at least in part, by injecting thymus or thoracic duct cells5, which demonstrates that recirculating lymphocytes are thymus-dependent although it does not prove that they are thymus-derived.
Article
CELLS which produce gammaG antibody are more dependent on the presence of a thymus than are those which produce gammaM antibody1. This conclusion is based on experiments carried out in lethally irradiated mice repopulated with foetal liver cells and grafted with a syngeneic thymus. Sinclair and Elliott2 have published data which suggest that the suppressive effect of thymectomy can be partly over-ridden by large doses of antigen. In normal mice immunized with sheep RBC the antigen-dose/plaque-forming cell (PFC) response is different for each class of antibody produced and most plaque-forming cells produce only one class of immunoglobin (unpublished work of D. W. Dresser, H. L. Anderson and H. H. W.). We have immunized thymectomized and non-thymectomized mice with different doses of sheep red blood cells (RBC) and have measured the response in terms of cells producing four different classes of immunoglobulin.
Article
A new method of passive immune lysis is presented. This method involves the coupling of protein antigen to chromic chloride-treated human erythrocytes. The kinetics of CrCl3 requirements, antigen dosage, and incubation are presented. The antigen-coated erythrocytes are lysed by an excess of rabbit complement. Experiments documenting the sensitivity and reproducibility of the test as well as the stability and fragility of CrCl3-treated erythrocytes are presented, and various advantages of the test are discussed.
Article
Differentiation between life and death in unicellular beings should be based upon criteria which are more convenient and fundamental than measurements of capacity for growth. The principle of ion (eosin) exclusion has been substantiated as a simple, rapid tool for this purpose. The conditions for valid observations in cell and tissue cultures have been delineated in respect to: eosin, serum and electrolyte concentrations. These simplified methods have replaced cultivation procedures in studies on: the effects of exposure to pancreatin and to drying, and the exposure of sensitive cells to tuberculin; storage of stock suspensions of cells without renewal of medium; and use of such methods for investigating nutritional or metabolic requirements.
Article
In rabbits, complete thymectomy before the age of 5 days produced immunologic deficiency in the adult animals, as indicated by reduced antibody production to bovine serum albumin and bacteriophage T(2). Homotransplantation immunity was unaffected, however. In an inbred strain of mice, complete neonatal thymectomy resulted in complete inability of the 60-day-old animals to form antibody to bacteriophage T(2). Inbred mice, completely thymectomized at birth, had a deficient homograft response, indicated by acceptance of skin homografts from strains differing in both the weaker and stronger (H-2) histocompatibility antigens. Tumor transplants (mammary adenocarcinoma) were also successful across the H-2 genetic barrier in mice thymectomized at birth. Neonatal thymectomy also eliminated the Eichwald-Silmser phenomenon, rendering female mice capable of accepting isografts of male skin. Transplantation immunity in mice was also affected by later thymectomy, at 30 days of age, in certain strain combinations involving weak histocompatibility differences. Spleen and lymph node cells from mice thymectomized at birth or at 6 days of age, and sacrificed 2 months later, did not produce a graft versus host reaction in appropriate F(1) hybrid recipients, indicating that such cells are immunologically inactive. Neonatal thymectomy of F(1) hybrid mice, and in one strain combination thymectomy at 40 days of age, produced animals with inordinate susceptibility to runt disease (homologous disease) following injection of parent strain spleen cells 35 days (neonatal surgery) and 10 days (surgery at 40 days) later. Mice thymectomized at birth also showed growth failure and were short-lived. Studies of newborn mice indicated that they have true lymphocytes only in the thymus, and lack such cells in the spleen, lymph nodes, and gut. In normal mice, adult lymphoid structure develops gradually, beginning during the 1st week of life and continuing for the next month. In contrast, mice thymectomized at birth do not develop mature lymphoid structure: the lymph nodes and spleens tend to be small and poorly organized, and show a quantitative deficiency in lymphoid cells. It is our current working hypothesis that the thymus makes a major contribution toward the centrifugal distribution of lymphoid cells which, in turn, is essential to the full expression of immunologic capacity.
Article
A clear-cut serological differentiation between AKR lymphocytes of thymic and non-thymic origin is reported: these two cell types are antigenically distinct. In newborn mice, the AKR thymic antigen was found at a high concentration only in thymus. In adult mice, the antigen was present at a high level in thymus, all nervous tissues tested, and some leukemias. It was present at much lower levels in lymph node lymphocytes, splenic lymphocytes, appendix, lung, and certain other leukemias, which appeared to be of non-thymic origin. The AKR thymic antigen was present at a high level in thymus and nervous tissues of RF mice, but was absent from thymocytes of sixteen other mouse strains. These sixteen strains possessed the C3HeB/Fe thymic antigen. The distribution of this antigen in neonatal and adult tissues of the strains tested was similar to that of the AKR thymic antigen in AKR mice. No exceptions were found. These results were obtained by use of immune cytolysis, and of a new method for the quantitative treatment of data from absorption experiments.
Article
Flagella of Pseudomonas fluorescens, Pseudomonas rhodos, Proteus vulgaris, Salmonella typhimurium and Bacillus subtilis were prepared for electron microscopy by several negative-contrast methods. Flagella attached to the cell and short detached pieces all gave the same results. Two types of structure (A and B) and a possible intermediate form were found; sometimes (Ps. rhodos) the structure changes along a single flagellum. The A structure shows helically connected globules aligned in longitudinal rows; sometimes there are also indications of longitudinal connexions. The B structure shows neither globules nor helices, but has thick longitudinal lines, the number of which in a given species is the same as the number of rows of globules in the A form.The globules in type A flagella alternate in adjacent longitudinal rows and are connected helically so that the number per turn of each helix equals the number of longitudinal rows. In the models proposed, this number is 10 in Ps. fluorescens, but 8 in all the other species examined. The spacing of the globules along each row is about 50 Å. This could account for the reflexions at 25·6 Å, etc., on the meridian of diffraction patterns (Astbury, Beighton & Weibull, 1955). The significance of the finding (Astbury, Beighton & Weibull, 1955) that the reflexions from Proteus flagella indicate a 410 Å periodicity (as in the act in-containing filaments of muscle) is discussed in the light of our results which indicate that the pitch of the globule helix is about 200 Å in Proteus, and about 250 Å in Ps. fluorescens. The question whether flagella, like muscles, might be two-component contractile systems is considered. It is interesting that helices of globular units (actin molecules), comparable in size to the globules in flagella, are present in all kinds of muscle. It remains to be shown if the structural changes found in the globule system in flagella have anything to do with contraction.
Article
Rats thymectomized at birth gained weight and otherwise developed normally, but were found to be very susceptible to intercurrent infections. Both Arthus reactivity and delayed hypersensitivity to BSA were markedly impaired in rats thymectomized during the first week of life and significantly impaired in rats thymectomized as late as 3 weeks after birth. The inhibition of Arthus reactivity in thymectomized rats was well correlated with their failure to develop significant titers of precipitating or hemagglutinating antibody. However, natural heteroagglutinin titers were not altered in these animals, and no abnormality of serum proteins, including gamma-globulin could be detected by paper electrophoresis. The loss of immunologic activity could not be corrected by injecting homogenates of spleen or thymus before and during the sensitization period. Splenectomy at birth did not influence Arthus or delayed reactivity.
Article
The adoptive secondary response of mice to conjugates of NIP (4-hydroxy-5-iodo-3-nitro-phenacetyl-) and DNP (2,4-dinitrophenyl-) is here used to elucidate the mechanism of cellular cooperation. The framework into which the experiments fit can be formulated as follows. Priming immunization raises a crop not only of specific antibody-forming-cell-precursors (AFCP) but also of specific helper cells. Upon secondary stimulation the helper cells serve a role as handlers or concentrators of antigen, thus enabling AFCP which would otherwise be incapable of reacting to initiate antibody synthesis. In this act of cooperation both cells recognise antigen; in the system examined here the helpers recognise carrier determinants and the AFCP recognise either the hapten or other carrier determinants.
Article
The response to the second antigen of a sequence of two related antigens appears to consist of two qualitatively different antibody populations. Antibodies specific for the second antigen are of primary-response quality while the antibodies which cross-react with the first antigen are of secondary-response quality.
Observations quoted by O. Syoberg and E. Moller. Antigen binding cells in tolerant animals
  • B Anderson
  • G Moller
Anderson, B., and G. Moller. 1970. Observations quoted by O. Syoberg and E. Moller. Antigen binding cells in tolerant animals. Nature (London). 228:780.
The amplification of thymus-influenced antigen reactive cells by complexes of polyadenylic-polyuridylic acids. Doctorate Thesis
  • P E Cone
Cone, P,. E. 1970. The amplification of thymus-influenced antigen reactive cells by complexes of polyadenylic-polyuridylic acids. Doctorate Thesis. University of Michigan, Ann Arbor, Michigan.
Cell co-operation in the immune response: the hypothesis of an antigen presentation mechanism
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Mitchison, N. A. Cell co-operation in the immune response: the hypothesis of an antigen presentation mechanism. Immunopathol. Int. Syrup. 6th. In press.
Immunochemical studies of bacterial flagellin. Doctorate Thesis
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Parish, C. R. 1969. Immunochemical studies of bacterial flagellin. Doctorate Thesis. University of Melbourne, Melbourne, Australia.
Mode of action of antilymphocyte serum on thymus derived lymphocytes. Doctorate Thesis
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Martin, W. J. 1969. Mode of action of antilymphocyte serum on thymus derived lymphocytes. Doctorate Thesis. University of Melbourne, Melbourne, Australia.