Interactions of human α/β and γ/δ T lymphocyte subsets in shear flow with E-selectin and P-selectin

We have compared the ability of human α/β and γ/δ T lymphocytes to adhere to selectin-bearing substrates, an interaction thought to be essential for homing and localization at sites of inflammation. Both T cell populations form rolling adhesions on E- and P-selectin substrates under physiologic flow conditions. Although equivalent to α/β T cells in binding to E-selectin, γ/δ T cells demonstrated greater ability to adhere to P-selectin that was purified or expressed on the surface of activated, adherent platelets. Under static conditions, 80% of γ/δ T cells and 53% of α/β T cells formed shear-resistant adhesions to P-selectin, whereas only 30% of γ/δ and α/β T cells adhered to E-selectin. Thee enhanced ability of γ/δ T cells to adhere to P-selectin cannot be attributed to differences in expression of the P-selectin glycoprotein ligand (PSGI-1), as all α/β T cells versus ~75% of γ/δ T cells expressed PSGL-1. Both cell populations expressed a similar percentage of the carbohydrate antigens sialyl Lewis(x) and cutaneous lymphocyte-associated antigen. Depletion of lymphocyte populations or T cell clones bearing these oligosaccharides with the monoclonal antibody CSLEX-1 and HECA-452, respectively, resulted in a substantial reduction in adhesion to E-selectin and slight reduction in adhesion to P-selectin under flow conditions. Treatment of cells with an endopeptidase that selectively degrades O-sialomucins such as PSGL-1, abolished P-selectin but not E- selectin adhesion. Removal of terminal sialic acids with neuramimidase or protease treatment of cells abrogated cell adhesion to both selectin substrates. These results provide direct evidence for the presence of distinct E- and P-selectin ligands on T lymphocytes and suggest that γ/δ T cells may be preferentially recruited to inflammatory sites during the early stages of an immune response when P-selectin is upregulated.