A STUDY ON BINDING OF SUSPENDED NODAL LYMPHOCYTES TO HIGH ENDOTHELIALVENULES IN SECTIONS OF FROZEN RAT LYMPH-NODES

Live lymphocytes were previously shown to bind selectively to endothel ial cells (HEV cells) of the high endothelial venules (HEVs) in sectio ns of frozen lymph nodes. This study examines aspects of the assay tha t have so far not been considered or which have been incompletely addr essed. It was found that bound lymphocytes form a cytoplasmic veil, an d that about half of them form small groups in which they are linked t ogether by cytoplasmic bridges. It was also found that at least 83% of the lymphocytes bind to HEV walls, but very unevenly, and that 5% als o bind to medullary venules. In addition, 31% of the lymphocytes were estimated to bind to the abluminal face of HEV cells and probably to t issue lymphocytes present in subendothelial spaces or in perivascular channels (spaces). This would reflect cell interactions occurring, in vivo, between HEV cells and/or subendothelial lymphocytes. It is sugge sted that antigen specificity of lymphocyte retention by HEV cells acc ounts for the uneven binding to HEVs.