Antigen Presentation in the Gut
The induction of T cell responses requires recognition of antigens in association with class II major histocompatibility complex (MHC) proteins and specialized antigen-presenting cells. Candidate antigen-presenting cells in the gut include dendritic cells, macrophages, B lymphocytes, mucosal epithel...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
1990-01-01
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| Series: | Canadian Journal of Gastroenterology |
| Online Access: | http://dx.doi.org/10.1155/1990/527602 |
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| Summary: | The induction of T cell responses requires recognition of antigens
in association with class II major histocompatibility complex (MHC) proteins
and specialized antigen-presenting cells. Candidate antigen-presenting cells in
the gut include dendritic cells, macrophages, B lymphocytes, mucosal epithelial
cells and endothelial cells. Dendritic cells isolated from normal human colon are
potent inducers of primary immune responses and express high levels of class lI
MHC proteins. Lamina propria macrophages display class II MHC proteins, can
present antigens to sensitized T cells, may process antigen and release interleukin-l, but suppress antigen presentation by intestinal dendritic cells in a
dose-dependent manner. Class II MHC molecules are normally expressed on
small intestinal epithelial cells but not on normal colonic epithelial cells.
Suppressor T cells and unresponsive T helper cells in the mucosa appear to
mediate systemic T cell tolerance of dietary antigens. In the inflamed colon there
is infiltration of the lamina propria by large numbers of monocytes which secrete
interleukin-1, and the release of interferon-gamma appears to induce class II
protein expression on colonic epithelial cells. Colonic epithelial cells from
inflamed bowel may preferentially stimulate T helper cells so that local induction
of class II MHC molecules on epithelial cells may amplify and localize secondary
immune responses at the site of inflamed mucosa. Taken together, the aberrant
expression of class II MHC molecules, breaches in epithelial cell integrity
(resulting m exposure to luminal antigens including endotoxin and the increased
numbers of monocytes found 10 inflamed mucosa suggest that the
resulting distortions in antigen presentation contribute to the localization and
persistence of the inflammatory lesion in inflammatory bowel disease. |
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| ISSN: | 0835-7900 |