ROLE OF LFA-1, CD2, VLA-5 CD29, AND CD43 SURFACE-RECEPTORS IN CD4(+) T-CELL ADHESION TO B-CELLS/

We investigated the adhesion to B cells of CD4(+) T cells both in the resting state and following activation by CD3 cross-linking or stimula tion by PMA/ionomycine/IL2 for 6 days. Both resting and activated CD4( +) T cell adhesion were inhibited by anti-LFA-1, -CD2, -VLA-5/CD29, an d -CD43 antibodies, suggesting coordinated upregulation of T cell adhe sion. The CD2 and LFA-1 adhesion pathways were found to act independen tly, as CD2 was functional in T cells not expressing LFA-1, and vice v ersa, and as specific antibodies had additive effects. In contrast, LF A-1- and VLA-5/CD29-specific antibodies did not have an additive block ing effect on CD4(+) T cell adhesion, suggesting that efficient adhesi on requires a competitive association of integrins with cytoskeleton e lements. Although the involvement of fibronectin (coated to B cells vi a VLA-4) in VLA-5-mediated T cell adhesion to B cells is feasible, an anti-fibronectin and a VLA-4-specific antibody had no blocking effect. The involvement of an unidentified B cell ligand can also be envisage d. (C) 1994 Academic Press, Inc.