EPITHELIAL DISPOSITION OF ANTIGEN

Exogenous antigens can impinge upon the luminal surface of mucous memb ranes and to a limited degree, can even penetrate into the lamina prop ria. As a result of infection, microbial antigens can be present in mu cosal epithelium or lamina propria. ill all three levels (lumen, epith elium, lamina propria), locally produced antibodies, principally immun oglobulin A (IgA), can combine with antigens. As a result, antigens ca n be prevented from attaching to the epithelium, viruses can be neutra lized inside epithelial cells and immune complexes in the lamina propr ia can be excreted into the lumen. As the Fc portion of IgA is special ized to facilitate epithelial transport of IgA rather than to activate inflammatory mediator systems (as is the case with other classes of i mmunoglobulin), the predominance of IgA among mucosal antibodies serve s to limit the degree of local inflammation following antigen-antibody reactions.