Lymphocyte trafficking: Adhesive interactions in secondary lymphoid organs

This thesis investigates adhesive interactions that may participate in lymphocyte migration through secondary lymphoid organs. Chapters two and three investigate lymphocyte binding to HEV, the fourth chapter investigates adhesion to tonsillar stromal cells and the fifth chapter describes lymphocyte binding to tenascin.; Chapter two describes a novel assay in which lymphocytes tether to and roll along the HEV of frozen sections of human lymphoid tissues before becoming firmly adherent. Firm adhesion but not binding and rolling is blocked by treatment of cells with azide and 2-deoxy- sc D-glucose or by pertussis toxin; firm adhesion is therefore dependent upon cell activation and G{dollar}sb{lcub}rm ai{rcub}{dollar} protein-linked receptors. These experiments support the three-step model of lymphocyte adhesion to HEV in humans.; The third chapter provides evidence for non-mucin L-selectin ligands on HEV that support lymphocyte binding. O-glycoprotease treatment of tissue sections eliminates HEV staining with MECA-79 but only partially reduces staining with two other sLe{dollar}sp{lcub}rm x{rcub}{dollar} mAbs, suggesting these mAbs recognize pools of both mucin- and non-mucin-linked sLe{dollar}sp{lcub}rm x{rcub}.{dollar} This O-glycoprotease-resistant pool of sLe{dollar}sp{lcub}rm x{rcub}{dollar} is shown to mediate tethering and rolling of lymphocytes to HEV of frozen tissue sections via L-selectin, an interaction not blocked by MECA-79 mAb. Therefore a pool of non-mucin sLe{dollar}sp{lcub}rm x{rcub}{dollar}-containing molecules exist on human HEV and can serve as L-selectin ligands.; Chapter four describes tethering and rolling of tonsillar lymphocytes and SKW3 cells under shear stress on monolayers of cultured tonsillar stromal cells via CD44 interactions with hyaluronan. SKW3 cells added under flow to frozen sections of human tonsil bind and roll along reticular fibers via CD44 and hyaluronan. Lymphocytes migrating through secondary lymphoid organs may therefore use CD44 to bind to hyaluronan immobilized on stromal cells and reticular fibers, facilitating migration.; The fifth chapter demonstrates that tenascin supports rolling of lymphocytes and lymphoblastic cell lines under flow conditions. Binding is calcium-dependent and mediated by the fibrinogen-like terminal domain of tenascin. Binding likely involves a novel tenascin receptor on lymphocytes. Lymphocyte binding to tenascin may be utilized during migration through secondary lymphoid organs.