REGIONAL EXPRESSION OF MURINE INTESTINAL IMMUNE CELLS IN NORMAL AND ISOGRAFTED INTESTINE

The spatial organization and differentiation of the gut immune system was studied using immunohistochemistry from Embryonic Day 15 until adu lthood. Leukocyte common antigen-positive cells were detected first, f ollowed by macrophages, B, and then T lymphocytes increasing in number and intensity of staining until adulthood. The adult mouse displays r egional localization of gut immune cells with highest expression in pr oximal intestine, decreasing distally to ileum with the fewest cells p resent in colon. The role of intestinal contents, bone marrow, and thy mus on maturation of the gut immune system during development was stud ied using an isograft model: small intestines from neonatal mice were implanted subcutaneously into SCID mice and developed into morphologic ally normal intestine. Injected syngeneic mononuclear cells recirculat ed to the isografted intestine and SCID host intestine with the same r egional expression as normal adult. This model is useful to define the mechanisms that establish and maintain cellular and regional differen tiation of the normal gut immune system. (C) 1995 Academic Press, Inc.