Immunohistochemical characterization of the lymphocyte and the immunoglobulin-containing cell in the epithelium and the lamina propria of normal human intestines.

In order to clarify difference of the mucosal immunity in various sites of normal large and small intestines, we studied the population of lymphocyte subsets and immunoglobulin (Ig)-containing cells in situ in biopsy specimens taken from various sites (ascending colon, sigmoid colon and rectum) of the large intestine and from the duodenum using an immunohistochemical method. Monoclonal antibodies against pan-T (Leu 1), cytotoxic/suppressor T (Leu2a), helper/inducer T (Leu3a), suppressor T (Leu15) and natural killer/K (Leu7) cells, and polyclonal antibodies to human IgG, IgA and IgM were used. In the duodenum, intraepithelial lymphocytes (IELs) were more prominent than in the large intestine. Immunoelectron microscopic observation revealed that some Leu2a+ IELs possessed pseudopods extending into intestinal epithelial cells, indicating that some IELs belong to the cytotoxic T cell subset. Leu7+ IELs were scarcely observed and Leu7+/Leu1+ ratio was higher in the large intestine than in the duodenum. Furthermore, the number of Leu7+ cells were more in the distal than the proximal colon. In the lamina propria Ig-containing cells tended to be fewer in the rectum than in the duodenum and the proximal colon. Our findings may suggest the variation of local immune responses and the difference of assigned immunological functions among the various sites of the intestines.