Specific expression of a complex sialyl Lewis X antigen on high endothelial venules of human lymph nodes: possible candidate for L-selectin ligand.
L-selectin is a cell adhesion molecule that mediates homing of lymphocytes to the peripheral lymph nodes and is speculated to bind to the carbohydrate determinant which is specifically expressed by the endothelial cells of high endothelial venules (HEVs) in the peripheral lymph nodes. One of the murine monoclonal antibodies (2H5, IgM, kappa), which was raised against sialyl LeX-active glycolipids which have long and complicated carbohydrate structures, was found to react strongly to the HEV endothelial cells of the human peripheral lymph nodes, while the typical anti-sialyl LeX antibodies SNH-3, FH-6 and CSLEX-1 failed to detect the antigen on HEV under the same condition. This new antibody was reactive to essentially all endothelial cells of HEV in the peripheral lymph nodes, and moderately to some endothelial cells in Payer's patches and appendices, but never reacted with the endothelial cells of post capillary venules in the spleen, thymus, or other organs. The 2H5 antibody detected three major glycoproteins of 90, 110 and 250 kDa, the most abundant molecular species being 110 kDa, in the stroma of human lymph nodes. In Stamper-Woodruff assays employing cryostat sections of human lymph nodes, the 2H5 antibody significantly inhibited the adhesion of peripheral lymphocytes to the endothelial cells of HEV. These results indicate that the carbohydrate antigens defined by the 2H5 antibody, most probably sialyl LeX determinants having complex carbohydrate structures, serve as the ligand for L-selectin on HEV endothelial cells.