Recirculation of Lymphocytes Through the Spleen

Abstract

The spleen is the most important organ of lymphocyte recirculation in man and rodents (Pabst 1988a). Recirculation implies the distribution of lymphocytes to all secondary lymphatic organs and other tissues by the blood, their emigration from the vasculature, a sojourn in the respective tissue and the subsequent return into the blood. In most tissues the route of lymphocyte return to the blood involves the lymphatic vessels and finally, the thoracic duct or other large lymph ducts joining the venous system. The case of the spleen is somewhat different, because recirculation implies extravasation, a period of lymphocyte arrest in the white pulp and subsequent direct re-entry into the venous effluent from the organ. Larger efferent lymphatics are clearly present in the vicinity of large arteries in the spleen of man and rodents (own observation; Pellas and Weiss 1990) and lymph capillaries occur in the human PALS (Van Krieken et al. 1985), but it is assumed that lymphatic drainage only plays a negligible role for lymphocyte recirculation through the spleen.