Professional and non-professional antigen-presenting cells in the porcine small intestine

We have previously presented evidence of a highly organized and compartment alized structure of the small intestinal lamina propria of the pig. In this work, we have identified at least two major populations of cells in this s ite expressing high levels of major histocompatibility complex (MHC) class II antigens. One is CD45 positive and is a potent initiator of a primary im mune response, this is a function usually associated with dendritic cells. These cells have characteristic dendritic morphology, but show evidence of phagocytosis as well as other phenotypic markers of immature dendritic cell s. Some cells show evidence of ongoing immune maturation. We have also isol ated CD45 negative endothelial cells bearing significant amounts of MHC cla ss II, which do not trigger a mixed lymphocyte reaction. These findings hav e implications for the functional role of healthy gut lamina propria and cl early implicate this site as capable of differential antigen presentation b y a heterogeneous population of antigen-presenting cells.