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IAH AC Gastrointestinal Disease

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The function of the mucosal lining<br />

as an immune organ<br />

• Permeability<br />

• MHC secretion<br />

• Antigen presentation<br />

• Secretory component<br />

• Adhesion molecule<br />

• Presentation<br />

• Immunocyte chemo<br />

• Attractants<br />

• Antimicrobial activity<br />

© <strong>IAH</strong> 2007<br />

7<br />

The epithelium itself plays a very important role in immunity.<br />

Through the integrity of the Tight Junction, the size of antigens is controlled, so<br />

that under normal physiological conditions, only small amounts of antigen is<br />

processed by the GALT. This leads to natural tolerance.<br />

The gut further secretes Major Histocompatibilty proteins, especially Type II<br />

which play a role in antigen presentation.<br />

The M cells interspersed between the epithelial cells are specialized Antigen<br />

Presenting cells.<br />

IgA is the major antibody active in the gut, but needs a secretory component to<br />

function.<br />

This is provided by the mucosal cells.<br />

The mucosa will also secrete chemokines which under special conditions will<br />

attract immune cells to the gut by virtue of chemotaxis.<br />

Lastly the gut lining will secrete several antimicrobial peptides, which plays a role<br />

in host defense.<br />

7

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