DISTRIBUTION OF SACCHARIDES IN PIG LYMPH-NODE HIGH-ENDOTHELIAL VENULES AND ASSOCIATED LYMPHOCYTES VISUALIZED USING FLUORESCENT LECTINS AND CONFOCAL MICROSCOPY

The distribution of saccharides in pig lymph nodes, particularly on hi gh-endothelial venule (HEV) endothelium and on lymphocytes in these ve ssels, was studied by examining the binding of fluorescent conjugates of 18 different lectins. Eight of the lectins, particularly with glyca n specificity restricted to mannose and polyacetyllactosamine determin ants, were found to bind with a high affinity to these structures. Com petitive inhibition experiments revealed that polylactosamine-containi ng glycans were present on endothelia and lymphocytes using lectins fr om Lycopersicon esculentum and Solanum tuberosum, the latter lectin re acting with lymphocytes only when apparently adherent to the luminal e ndothelium. The absence on pig endothelium of the Ulex europaeus bindi ng, shown by human endothelia due to the presence of certain fucose ep itopes, was confirmed. Pig lymph-node endothelium, however, bound the fucose-specific lectin of Tetragonolobus purpureas, indicating the pre sence of fucose on pig endothelia in a different conformation to that seen on human endothelia. The results suggested that pig lymph-node HE V endothelium expressed a core fucosylated tri- or tetra-antennary com plex glycan with polylactosamine extensions and expressing an Le(y) de terminant.