[Show abstract][Hide abstract] ABSTRACT: Administration of therapeutic proteins by methods other than injection is limited, in part, by inefficient penetration of epithelial barriers. Therefore, unique approaches to breaching these barriers are needed. The neonatal constant region fragment (Fc) receptor (FcRn), which is responsible for IgG transport across the intestinal epithelium in newborn rodents, is expressed in epithelial cells in adult humans and non-human primates. Here we show that FcRn-mediated transport is functional in the lung of non-human primates and that this transport system can be used to deliver erythropoietin (Epo) when it is conjugated to the Fc domain of IgG1. FcRn-dependent absorption was more efficient when the EpoFc fusion protein was deposited predominantly in the upper and central airways of the lung, where epithelial expression of FcRn was most prominently detected. To optimize fusion protein absorption in the lung, we created a recombinant "monomeric-Epo" Fc fusion protein comprised of a single molecule of Epo conjugated to a dimeric Fc. This fusion protein exhibited enhanced pharmacokinetic and pharmacodynamic properties. The bioavailability of the EpoFc monomer when delivered through the lung was approximately equal to that reported for unconjugated Epo delivered s.c. in humans. These studies show that FcRn can be harnessed to noninvasively deliver bioactive proteins into the systemic circulation in therapeutic quantities.
Full-text · Article · Jul 2004 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Mucosal secretions of the human gastrointestinal, respiratory, and genital tracts contain the immunoglobulins (Ig)G and secretory IgA (sIgA) that function together in host defense. Exactly how IgG crosses epithelial barriers to function in mucosal immunity remains unknown. Here, we test the idea that the MHC class I-related Fc-receptor, FcRn, transports IgG across the mucosal surface of the human and mouse lung from lumen to serosa. We find that bronchial epithelial cells of the human, nonhuman primate, and mouse, express FcRn in adult-life, and demonstrate FcRn-dependent absorption of a bioactive Fc-fusion protein across the respiratory epithelium of the mouse in vivo. Thus, IgG, like dimeric IgA, can cross epithelial barriers by receptor-mediated transcytosis in adult animals. These data show that mucosal surfaces that express FcRn reabsorb IgG and explain a mechanism by which IgG may act in immune surveillance to retrieve lumenal antigens for processing in the lamina propria or systemically.
Full-text · Article · Sep 2002 · Journal of Experimental Medicine
[Show abstract][Hide abstract] ABSTRACT: The human major histocompatibility complex (MHC) on chromosome 6 encodes three classical class-I genes: human leukocyte antigens (HLA) A, B, and C. These polymorphic genes encode a 43- to 45-kDa cell surface glycoprotein that, in association with the 12-kDa beta2-microglobulin molecule, functions in the presentation of nine amino acid peptides to the T-cell receptor of CD8-bearing T lymphocytes and killer inhibitory receptors on natural killer cells. In addition to these ubiquitously expressed, polymorphic proteins, the human genome also encodes several nonclassical MHC class-I-like, or class Ib, genes that, in general, encode nonpolymorphic molecules involved in various specific immunological functions. Many of these genes, including CD1, the neonatal Fc receptor for IgG, HLA-G, HLA-E, the MHC class-I chain-related gene A, and Hfe, are prominently displayed on epithelial cells, suggesting an important role in epithelial cell biology.
[Show abstract][Hide abstract] ABSTRACT: The toxicity of the staphylococcal enterotoxins (SEs) has been linked to the activation of large numbers of T cells in the peripheral lymphoid tissues. Because the primary manifestations of foodborne enterotoxic poisoning are associated with the gastrointestinal tract, we have compared the responses of T cells in the gut-associated lymphoid tissue and in the periphery to intragastric (i.g.) and i.p. administration of SEB. Intraperitoneal SEB results in an early expansion of peripheral Vbeta8+ T cells and Th1 cytokine secretion followed by deletion at 7-10 days. We found that i.g. SEB rapidly (within 4 h) leads to the expansion and activation of Vbeta8+ T cells in the Peyer's patch and mesenteric lymph nodes. Analysis of cytokine mRNA in purified Vbeta8+ T cells by competitive RT-PCR showed that, 4 h after i.g. SEB, the induction of mRNA for IL-2 and IFN-gamma is about 10-fold greater in mucosal than in peripheral lymphoid tissue. Our results show that activated mucosal T cells expand and up-regulate cytokine mRNA in response to luminal exposure to SEB, suggesting a role for the gut-associated lymphoid tissue in the gastrointestinal manifestations of enterotoxic poisoning.
Preview · Article · Jan 1999 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Spontaneous inflammatory bowel disease (IBD) resembling human ulcerative colitis develops in mice mutant for the T cell receptor alpha gene (TCR-alpha-/-). TCR-alpha-/- mice lack TCR-alpha/beta+ cells but contain TCR-gamma/delta+ cells and a small population of a unique CD4+, TCR-alpha-/beta+(low) cells. Since all the immunoglobulin (Ig) classes are present in these mice, help to B cells must be provided by cells other than TCR-alpha/beta+ cells. In the present study, we found serum levels of IgG1 and IgG2 to be markedly increased in TCR-alpha-/- mice with IBD as compared to TCR-alpha-/- mice without IBD or TCR-alpha+/- controls. An increase in IgG1-, IgG2a- and IgA- but not IgM-secreting mesenteric lymph node (MLN) B cells was detected in TCR-alpha-/- mutant mice. There was also a marked increase in MLN B cells secreting autoantibody (IgG) to tropomyosin, a cytoskeletal protein. Examination of the hyperplastic MLN showed a marked increase in the number of B, TCR-delta+, and CD4+ TCR-alpha-/beta+ cells, similar to the cell population observed at the site of colonic inflammation. Analysis of spontaneous cytokine production by MLN cells using an enzyme-linked immunospot assay, immunohistochemistry, and reverse transcription/polymerase chain reaction showed a decrease of interleukin 2 (IL-2) but a marked increase of IL-4 and interferon gamma (IFN-gamma) production in TCR-alpha-/- mice with IBD as compared to TCR-alpha-/- mice without IBD and TCR alpha+/- control mice. Both TCR-alpha-/beta+ and TCR-delta+ cells were found to be capable of producing IL-4; IFN-gamma was produced mostly by non-T cells, many of which were shown to be CD3- NK 1.1+ cells. We propose that the cytokine imbalance present in these mice results in expansion of B cells, production and switching of autoantibodies to IgG2 subclass, and development of IBD. It is possible that the unusual CD4+ TCR-alpha-/beta+ population and expanded TCR-gamma/delta+ population present in TCR-alpha-/- mice plays a central role in this abnormal immune response.
Full-text · Article · Apr 1996 · Journal of Experimental Medicine