Antigen uptake and trafficking in human intestinal epithelial cells

Primacy intestinal epithelial cells, human colonic adenocarcinoma cell line s (DLD-1, Caco-2, and HT-29), and monocytes were used as model systems to s tudy antigen uptake, antigen-presenting cell properties, as well as the kin etics of antigen uptake in intestinal epithelial cells (IEC), Intracellular staining of fluoresceinated tetanus toroid was not evident in the IEC unti l after 30 min of incubation at 37 degrees C, whereas in monocytes intracel lular punctate staining of fluoresceinated tetanus toroid was evident after 5 mins. In polarized Caco-2 cells antigen could be internalized at both th e apical and basolateral surfaces with polarized transport. When analyzed b y electron microscopy, gold-labeled tetanus toroid was internalized and fou nd within endosomes and multivesicular bodies, but not within the lysosomal compartments by 60 min. By 2 hrs, gold-labeled tetanus toroid was evident in the secondary lysosomes, These results demonstrate that tetanus toroid f ollows an endocytic pathway in intestinal epithelial cells and that the kin etics of antigen uptake is slower than that of conventional antigen-present ing cells.