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 high-endothelial venule (HEV) endothelium and on lymphocytes in these vessels, was studied by examining the binding of fluorescent conjugates of 18 different lectins. Eight of the lectins, particularly with glycan specificity restricted to mannose and polyacetyllactosamine determinants, were found to bind with a high affinity to these structures. Competitive inhibition experiments revealed that polylactosamine-containing glycans were present on endothelia and lymphocytes using lectins from Lycopersicon esculentum and Solanum tuberosum, the latter lectin reacting with lymphocytes only when apparently adherent to the luminal endothelium. The The absence on pig endothelium of the Ulex europaeus binding, shown by human endothelia due to the presence of certain fucose epitopes, was confirmed. Pig lymph-node endothelium, however, bound the fucose-specific lectin of Tetragonolobus purpureas, indicating the presence of fucose on pig endothelia in a different conformation to that seen on human endothelia. The results suggested that pig lymph-node HEV endothelium expressed a core fucosylated tri- or tetra-antennary complex glycan with polylactosamine extensions and expressing an Ley determinant.