Immunocytochemical studies of the vascular endothelial cells in human Peyer's patches and solitary lymphoid follicles.

The present immunohistochemical study of human Peyer's patches and solitary lymphoid follicles have revealed that the PCV in these thymus-dependent areas has a specialized endothelium to which T and B lymphocytes generated in these follicles selectively adhere and then penetrate. The PCV endothelium shares antigens with a peripheral monocyte or macrophage subset which is HLA-DR+, OK-M5+ and OK-M1-. The presence of such antigens could be responsible for regulation of the lymphocyte passage through the venules, and for lymphocyte maturation, activation and proliferation during the migration. A possible route used by the lymphocytes traversing the PCV endothelium is discussed.