COMPLEXITY AND DIFFERENTIAL EXPRESSION OF CARBOHYDRATE EPITOPES ASSOCIATED WITH L-SELECTIN RECOGNITION OF HIGH ENDOTHELIAL VENULES

Carbohydrate ligands for lymphocyte L-selectin are expressed on high e ndothelial venules (HEVs) in peripheral lymph nodes and sites of chron ic inflammation and mediate the recruitment of lymphocytes from the bl ood into these tissues, In the mouse, these ligands, collectively term ed the peripheral lymph node addressin (PNAd), have been shown to cont ain fucose, sialic acid, and sulfate and to include several HEV glycop roteins including GlyCAM-1, CD34, and MAdCAM-1, Monoclonal antibody (M Ab) MECA-79, which binds a sulfate-dependent epitope, recognizes PNAd in both mouse and man, In humans, only CD34 has been identified among the glycoprotein species that react with MECA-79, Although P-selectin is highly expressed in tonsil HEVs, it was not found to react with MEC A-79 or to support L-selectin-mediated lymphocyte rolling, To further characterize human PNAd, MAbs were developed against purified PNAd imm unoisolated from human tonsil. MAbs JG-1, JG-5, JG-9, and JG-10, like MECA-79, bind HEVs in human tonsil and react similarly in Western blot s, and JG-9 and JG-10 also block lymphocyte rolling on purified PNAd, In addition, by competitive ELISA on purified tonsil PNAd, all MAbs we re found to react with overlapping epitopes. However, JG-1, JG-5, JG-9 , and JG-10 do not recognize mouse PNAd, and unlike MECA-79, they reco gnize determinants that are sensitive to neuraminidase, Strikingly, th e epitope recognized by JG-1, although abundant in tonsil and peripher al lymph node, is absent from appendix HEVs or HEVs in some samples of chronically inflamed skin, even though these HEVs are MECA-79 reactiv e, Moreover, although JG-5 and JG-9 react well with tonsil, peripheral lymph node, and inflamed skin HEVs, they react only with occasional e ndothelial cells in appendix tissues, These findings point to signific ant diversity in the carbohydrate determinants expressed by HEVs and r ecognized by L-selectin and demonstrate their differential representat ion in different sites in vivo, These antibodies should be useful in p robing the precise structure of human L-selectin ligands.