Differences in lymphocyte subsets in the wall of high endothelial venules and the lymphatics of human palatine tonsils.

Lymphocyte trafficking plays a critical role in disseminating specifically primed lymphocytes all over the body. Most concepts on the interaction of adhesion molecules on lymphocyte subsets and specialized endothelia such as those in high endothelial venules (HEV) are based on animal experiments as kinetic studies cannot be performed in humans. We therefore characterized lymphocyte subsets in the wall of HEV and in the lumen of lymphatics of 18 human palatine tonsils by immunohistology. All subsets studied were found in the wall of HEV (% of lymphocytes): 32% CD20+, 50% CD3+, 14% CD4+, 32% CD8+ and also 21% CD45RA+ and 39% CD45RO+. In the lymphatics, used to indicate lymphocytes emigrating from the tonsils, a different composition was found; e.g. many more T cells and three times more CD45RA+ than RO+ lymphocytes. Thus, HEV are not a selective entry site nor lymphatics an exit for specific lymphocyte subsets only, at least in these tonsils with chronic stimulation.