THE MIGRATION OF LYMPHOCYTES ACROSS SPECIALIZED VASCULAR ENDOTHELIUM

The chain of lymph-nodes in the rat mesentery was isolated and the preparation was perfused via cannulae in the superior mesenteric vessels. The perfusate consisted of serum to which labelled lymphocytes had usually been added. The entry of radioactively labelled lymphocytes from the blood vessels into the lymph-nodes was studied by scintillation counting and autoradiography. It was observed that: (1) In the perfused node labelled lymphocytes localized in and around post-capillary venules in the paracortex as they do early after i.v. injection. (2) The number of lymphocytes which entered the node was directly proportional to the concentration in the perfusate over the range studied. The proportion of cells retained in the node varied considerably around a mean of 11 % of lymphocytes reaching it. (3) The isolated lymph-node released few if any lymphocytes into the effluent (venous) perfusate. (4) Large lymphocytes migrated into isolated lymph-nodes slightly more readily than did small lymphocytes. (5) Unlike intact cells isolated lymphocyte membranes did not adhere to specialized vascular endothelium.