Immunological importance of the second gut segment of carp. I. Uptake and processing of antigens by epithelial cells and macrophages

Abstract

Uptake and transport of soluble (ferritin) and particulate ( Vibrio anguillarum ) antigen from intestinal lumen to mucosal macrophages was studied using immunocytochemical and electron‐microscopical techniques. Both antigens were taken up by epithelial cells of the second gut segment, reached the supranuclear vacuoles and were finally transported to large intraepithelial macrophages. In contrast with particulate antigen, antigenic determinants of ferritin were demonstrated in the basal part of the epithelium and appeared to be released at the mucosal site. After anal intubation many small macrophages penetrated the intestinal epithelium, took up antigen and after 24 h disappeared again from the intestinal mucosa. This feature was antigen independent and also occurred after anal PBS‐intubation. The larger, less mobile macrophages stayed in the intestinal epithelium and finally exposed antigenic determinants (of both antigens) at their outer surface, suggesting an antigen‐presenting function. Whether these large macrophages can induce a local or mucosal immune response and whether the smaller mobile macrophages are involved in a systemic response is discussed.