Leukocyte function-associated antigen 1 (LFA-1) and CD44 are signalling molecules for cytoskeleton-dependent morphological changes in activated T cells.

Signaling through the leukocyte function-associated antigen 1 (LFA-1) molecule has previously been shown to induce homotypic aggregation in T cells and to induce cytoskeletal changes in T lymphoma cells. In this study we describe the induction of a dendritic phenotype associated with cytoskeletal rearrangement in activated human peripheral blood T cells stimulated with monoclonal antibody SPV-L7 to LFA-1 alpha. Maximal expression of this phenotype required 72 h preactivation with phorbol myristate acetate and expression was abolished using the protein kinase C inhibitor staurosporine. Monoclonal antibody to CD18, the beta-chain of LFA-1, did not induce this phenotype. Monoclonal antibody MEM 83 to presumably a discrete epitope on LFA-1 alpha did not induce this phenotype but induced homotypic aggregation. However, a monoclonal antibody to CD44 induced a similar phenotype in activated lymphocytes. Induction of both homotypic in activated lymphocytes. Induction of both homotypic aggregation and the dendritic phenotype was abolished by preincubation with soluble intracellular adhesion molecule 1 (ICAM-1). Cytoskeletal inhibitors prevented the morphological changes in SPV-L7-activated lymphocytes. Preincubation with tyrosine kinase inhibitor, protein kinase C inhibitors, and inhibitors of new protein synthesis also prevented these morphological changes. These data suggest that discrete epitopes on LFA-1 alpha may be capable of inducing discrete signals either for homotypic aggregation or for a dendritic phenotype. As both LFA-1 and CD44 are involved in the migration of lymphocytes through high endothelial venules, these data could suggest that these molecules transduce signals resulting in cytoskeletal modification necessary for lymphocyte transmigration.