T cell distribution is different in follicle-associated epithelium of human Peyer's patches and villous epithelium.

Immunohistochemical analyses performed on specimens of normal human ileum showed a significantly raised number of T cells in the follicle-associated epithelium (FAE) of Peyer's patches compared with the epithelium of distant villi. The T cells tended to be clustered in all layers of the FAE and were significantly more numerous adjacent to interruptions of the brush border (revealed by lack of staining for alkaline phosphatase). Such interruptions were taken to indicate 'membrane' (M) cells. Our findings therefore suggested a spatial relationship between M cells and the aggregation of T cells. The ratio of CD4+ to CD8+ T cells (approximately 4:10) was significantly higher in the FAE than in the villous epithelium (approximately 0.6:10). This suggested that the FAE may be involved to a greater extent in induction of 'helper' T cell functions, perhaps depending on luminal antigens transported by M cells, whereas the villous epithelium may be more involved in stimulation of 'suppressor' T cell functions as indicated by recent studies in vitro.