Antigen uptake and trafficking in human intestinal epithelial cell lines.
Item
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Title
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Antigen uptake and trafficking in human intestinal epithelial cell lines.
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Identifier
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AAI9510720
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identifier
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9510720
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Creator
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So, Agnes LaiPing.
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Contributor
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Adviser: Lloyd Mayer
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Cell | Biology, Microbiology | Health Sciences, Immunology
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Abstract
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In addition to its physiological function as an absorptive cell, the intestinal epithelial cell plays an active role in regulating gut mucosal immune responses. Several laboratories have demonstrated the antigen presenting cell properties of intestinal epithelial cells (IEC) in vitro. In the presence of soluble antigens, the IEC from rats, mice or humans can induce MHC-restricted antigen-specific T cell proliferation. Most interestingly, the T cell population activated by the IEC are predominately CD8+ suppressor T cells. The exact mechanisms of CD8+ suppressor T cell activation by IEC are still not fully understood. One plausible contributing factor may be that antigens are handled differently by the IEC when compared with conventional antigen presenting cells (APC) in systemic immunity. To define the unique properties of IEC, the pathways that IEC employ to handle antigens were compared and contrasted with those of conventional APC. Utilizing fluorescence, electron, and laser scanning confocal microscopy, we showed that the kinetics of antigen uptake by IEC lines was slower when compared with that of monocytes. Fluorescein-conjugated tetanus toxoid was internalized only after 30 min incubation at 37{dollar}\sp\circ{dollar}C compared with 5 min for monocytes. However, similar to monocytes, exogenous soluble protein antigens were taken up by fluid phase endocytosis and followed a classical class II pathway from early endosomes to late endosomes and subsequently into lysosomal compartments. The observation that tetanus toxoid (gold-labeled or fluorescein-labeled) resided in endosomal and lysosomal compartments may have significance with respect to the site(s) of antigen processing in IEC since MHC class II molecules have been demonstrated in these compartments. In the polarized intestinal epithelial cell line, Caco-2, antigen applied apically did not traffic to the basal cytoplasm but remained in apical lysosomal compartments, whereas antigen applied basally transcytosed to the apical cytoplasm. We also analyzed factors (antigen size, immune complexes, and prophagocytic cytokines) which might alter antigen uptake by IEC. Our data showed that, similar to monocytes, the size of antigen (e.g. OVA, KLH) played no role in antigen uptake. However, in contrast to phagocytic monocytes, IEC failed to take up insoluble antigens. Prophagocytic cytokines (IFN-{dollar}\gamma{dollar} or GM-CSF) and soluble immune complexes did not enhance antigen uptake while they did in monocytes. Taken together, our findings show that antigen uptake by IEC is a tightly regulated and stable process. While IEC are less efficient APC when compared with monocytes, the manner whereby antigen is handled may play an important role in maintaining a suppressed immunologic tone in the gastrointestinal tract.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
