[Show abstract][Hide abstract] ABSTRACT: A novel monoclonal antibody (MIL 11) specific for an antigen expressed on porcine endothelial cells is described. The antigen recognized by MIL 11 is most strongly expressed in the intestine but is also expressed on the capillary endothelium of a wide range of tissues. Using two- and three-colour immunofluorescence microscopy we demonstrated the extensive coexpression of MIL 11 and major histocompatibility complex (MHC) class II antigens on normal porcine capillary endothelium in the intestine, trachea, thymus and small veins, while endothelium of large vessels and the heart were negative for MHC class II. In contrast to humans and rodents, available reagents do not detect MHC class II on the intestinal epithelium of pigs. However, porcine intestinal endothelium expressed both DR and DQ antigens. A population of strongly class II-positive cells was also detected immediately adjacent to the endothelium in the lamina propria. Three-colour immunofluorescence microscopy highlighted the close association between endothelium and intestinal CD4+ T cells. Lamina propria T cells were mainly MHC class II positive, whereas those in the epithelial compartment were MHC class II negative.
[Show abstract][Hide abstract] ABSTRACT: The gastrointestinal immune system is presented with a contrasting array of antigens, ranging from harmless dietary components to highly pathogenic microorganisms. The mucosal immune system has the ability to recognise different groups of antigens and has evolved a battery of responses from which an appropriate response may be orchestrated. The question as to how the mucosal immune system categories antigens and selects a particular response is central to this process but it remains largely unanswered. The solution to this question is likely to hold the key to the development of safe and effective mucosal vaccines as well as suggesting methods for the prevention and control of allergic responses. Enteric diseases resulting from antigens (microbial and dietary) presented via the gastrointestinal tract are a major cause of morbidity and mortality. In addition to being of substantial economic importance, growing public awareness on animal welfare and food quality confirms the urgent need for new methods of disease control.
No preview · Article · Nov 1994 · Veterinary Immunology and Immunopathology
[Show abstract][Hide abstract] ABSTRACT: The ability of cholera toxin B-subunit to bind to intestinal epithelium and in particular the dome epithelium of the Peyer's patch can account for its potency as an immunogen. However, pure B-subunit is a less effective immunogen than whole cholera toxin. The immunogenicity of B-subunit may be restored by the addition of either traces of whole toxin or by pertussis toxin. Cholera toxin and pertussis toxin were both able to stimulate a response when fed in conjunction with keyhole limpet haemocyanin, whereas recombinant B- subunit of heat-labile toxin from Escherichia coli had no effect, demonstrating that the adjuvant action is a property of the enzymically active A-subunits. The adjuvant activity of both pertussis toxin and cholera toxin may be due to their ability to cause an increase in the activity of adenylate cyclase via their action on GTP-binding regulatory proteins. However, feeding of forskolin, a direct activator of adenylate cyclase, had no effect on the mucosal immune response, indicating a role for cholera and pertussis toxin which is independent of enhancement of adenylate cyclase activity in the regulation of the immune response. Antibody to pertussis toxin was not detected, which was attributed to inadequate absorption of pertussis toxin.
[Show abstract][Hide abstract] ABSTRACT: Major histocompatibility complex (MHC) class II antigens were identified on cells within mammary gland connective tissue of lactating mice using a paraformaldehyde-lysine-periodate-gluteraldehyde fixative and an immunoperoxidase staining method. The distribution of class II expressing cells within interalveolar and interlobular connective tissue was similar both throughout lactation and in successive lactations. Epithelial cells within secretory alveoli and mammary ducts did not express class II antigens.
No preview · Article · Feb 1993 · Immunology Letters
[Show abstract][Hide abstract] ABSTRACT: Spleen cells, but not mesenteric lymph node cells, from 3-week-old piglets abruptly weaned onto a soya-based diet, produced less interleukin-2 (IL-2) following non-specific activation with concanavalin A (Con A) than did cells from age- and litter-matched, unweaned controls. In contrast, the ability to express receptors for IL-2 was only marginally reduced. The effect on IL-2 production was most marked in animals weaned for as little as 24-48 h. Variation within groups increased with time after weaning, indicating differences between individuals in the longer-term effects of weaning. This finding may be due to endogenous production of steroids resulting in generalised impaired immune function or to retention of cells within intestinal sites owing to an active local immune response.
No preview · Article · Dec 1992 · Veterinary Immunology and Immunopathology
[Show abstract][Hide abstract] ABSTRACT: PROBIT estimates biologic activity by weighted probit regression analysis and comparison with a known standard. The program is intended to speed up calculation of the concentration of cytokines in large numbers of cell supernatants. Data are input from either sequential or free-form text files created with a spreadsheet or text editor. This allows transfer of data from a beta-counter equipped with a suitable terminal without retyping. Results are displayed and/or printed as relative potency (% of standard) and 50% effective dose (ED50).
No preview · Article · Sep 1992 · Journal of Immunological Methods
[Show abstract][Hide abstract] ABSTRACT: To understand the local immune events which occur when a novel antigen is encountered in the gut it is necessary to know whether cells from the mucosal tissues are capable of initiating T-cell reactivity. We have examined the capacity of cells isolated from the Peyer's patches and the lamina propria of the murine small intestine to present keyhole limpet haemocyanin (KLH) to naive syngeneic splenic T cells in vitro. The properties of the gut antigen-presenting cells (APC) were compared with those of cells from the spleen and the mesenteric lymph nodes. Results clearly demonstrate that cells from the lamina propria as well as from the Peyer's patches, mesenteric lymph node and spleen can present KLH to naive T cells, inducing strong proliferative reactions comparable in magnitude and kinetics. All the APC populations tested induced interleukin-2 (IL-2) production in primary cultures, although minor differences were noted when lamina propria cells were used as APC. IL-4 was not detected in supernatants from cultures of non-immune T cells in the presence of APC from any tissue. Phenotypic analysis of the cells in cultures of naive T cells, with antigen and APC from different gut-associated tissues revealed important differences. Cells from Peyer's patch, mesenteric lymph node and spleen gave rise to cultures containing largely CD4+CD8- cells. However, cultures in which lamina propria cells acted as APC consisted primarily of CD4-CD8+ cells.
[Show abstract][Hide abstract] ABSTRACT: Cholera toxin is widely recognized as a potent stimulator of mucosal IgA responses after oral feeding. However, comparatively little is known of its ability to stimulate cellular responses. This is due in part to the direct inhibitory effects of cholera toxin on T lymphocytes, which can confound attempts to study primed T-cell responses in vitro. We have avoided this problem by using cholera toxin as an adjuvant to enhance the response to an unrelated protein fed simultaneously. Thus the simultaneous feeding of 10 micrograms of cholera toxin and 5 mg of keyhole limpet haemocyanin (KLH) results in the priming of T cells in the spleen, mesenteric lymph nodes, Peyer's patch and lamina propria that proliferate when restimulated with KLH in vitro. The feeding of KLH alone does not result in such responses. Both CD4- and CD8-positive antigen-specific T cells were involved in the response and the cells produced both interleukins 2 and 4 on antigen restimulation in vitro.
[Show abstract][Hide abstract] ABSTRACT: Cholera toxin (CT) is a potent stimulator of IgA responses when administered orally and has been shown to promote IgA responses to a second protein such as keyhole limpet haemocyanin (KLH) if this is fed simultaneously. In this paper we show that whilst feeding 5 mg KLH with either 0.5 micrograms CT or 10 micrograms B subunit fails to stimulate a mucosal IgA response to KLH, feeding 0.5 microgram CT and 10 micrograms B subunit together with 5 mg KLH produces a local IgA anti-KLH response as great as that produced by 10 micrograms of whole CT. In addition to stimulating IgA responses in the lamina propria, preliminary results indicate that cellular responses are also stimulated, as we have demonstrated KLH antigen-driven proliferation of cells isolated from groups of mice fed either 10 micrograms CT + 5 mg KLH or 0.5 micrograms CT + 10 micrograms CTB + 5 mg KLH but not mice fed KLH alone or with either 10 micrograms CTB or 0.5 micrograms CT. These results indicate that the mucosal adjuvant action of CT is due to a synergistic effect involving both the GM1 binding of the B subunit and adenylate cyclase activation by the A subunit.
No preview · Article · May 1990 · Scandinavian Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Density and distribution of Ia antigen in the small intestine of C57bl/6 mice showed substantial differences, depending on the environment in which they were reared and maintained. Isolator-reared mice expressed low levels of epithelial Ia antigen in comparison to mice reared in a conventional environment. Oral administration of 10 micrograms of cholera toxin had no effect on the level of epithelial Ia expression. We conclude, therefore, that the mechanism whereby cholera toxin is able to potentiate mucosal responses to fed antigens is not related to changes in the level of epithelial Ia expression.
No preview · Article · Feb 1990 · International archives of allergy and applied immunology
[Show abstract][Hide abstract] ABSTRACT: We examined the effect of orally administered cholera toxin (CT) on the immune response to keyhole limpet haemocyanin (KLH) and ovalbumin (OVA) in high (C57Bl/6 H2b), medium (CBA H2k), and low (BALB/c H2d) responder I-A haplotypes to CT. Mice were fed OVA or KLH on three occasions at 10-day intervals and the effect of simultaneous feeding of CT determined. Isotype-specific antibody levels were assayed in serum samples collected 7 days after the last immunization. Antibody was also measured in the supernatant of gut explant cultures incubated at either 4 or 37 degrees C. Increased antibody levels in cultures kept at 37 degrees C indicated release of local intracellular antibody. Cholera toxin exerted an adjuvant effect on the mucosal response of all three strains to KLH and OVA. Overall, the responses to CT and the second protein were not correlated; we interpret these findings to indicate that while CT had an effect on the mucosal immune system which enhances the immune response to itself and other protein antigens, the final outcome of the response to the second antigen is dependent on differences in the ability of the strains to process, recognize, and respond to a particular antigen.
No preview · Article · Jul 1989 · Scandinavian Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Pigs weaned at three weeks old absorb food protein antigens from the intestine. The amount of antigen absorbed declines over the next three weeks, and this decline is associated with an increasing level of serum antibody to the fed proteins. There was no difference in the rate of immune elimination of intravenously injected antigen in fed and unfed controls. The reduction of serum antigen is thus likely to reflect reduced absorption, possibly mediated by locally produced antibody. Pigs weaned at 10 weeks old also absorbed antigens and produced an antibody response when introduced to soya; and after three weeks of feeding soya the absorption of antigen was substantially reduced. This latter exclusion was specific for soya as a second novel protein (ovalbumin) was absorbed when introduced to the diet at this time. At six months, pigs no longer absorbed soya proteins when they were introduced to the diet. Furthermore, pigs of this age had serum 'antibody' to soya and other proteins such as keyhole limpet haemocyanin to which they had never been exposed.
No preview · Article · Apr 1989 · Research in Veterinary Science
[Show abstract][Hide abstract] ABSTRACT: Transient hypersensitivity reactions of the intestinal immune system to dietary antigens result in increases in enterocyte turnover and villous atrophy. These changes occur in the intestine of the post weaned piglet and precede the proliferation of E. coli and the development of post-weaning diarrhea. We therefore postulated that a transient cell mediated immune response to dietary antigens may increase susceptibility to disease. The interaction of dietary and microbial antigens upon the gut immune system has been investigated in mice and pigs and it has been shown that both exert powerful regulatory effects upon each other.
No preview · Article · Jan 1988 · Veterinary Immunology and Immunopathology
[Show abstract][Hide abstract] ABSTRACT: We have examined the morphology and functional characteristics of porcine intraepithelial lymphocytes (IEL). A subpopulation of IEL contains granules as seen in other species, and their ultrastructure was also similar. They were capable of producing T-cell growth factor and interferon on in vitro stimulation. IEL killed P815 cells in the presence of PHA, but did not kill K562 cells.
[Show abstract][Hide abstract] ABSTRACT: Intraepithelial lymphocytes (IEL) were isolated from the small intestine of pigs. They showed a strong blastogenic response to the T-cell mitogens phytohaemagglutinin A (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM); in contrast, mouse IEL responded weakly to these mitogens. The response of pig IEL was age-dependent, reaching adult levels by 9 weeks of age. Early weaning of pigs delayed the onset of this response. The effects of inflammatory mediators on the response of mouse IEL were also examined.