PROTEIN-TYROSINE KINASE P56-LCK REGULATES LYMPHOCYTE FUNCTION-ASSOCIATED-1 ADHESION MOLECULE EXPRESSION, GRANULE EXOCYTOSIS, AND CYTOLYTIC EFFECTOR FUNCTION IN A CLONED T-CELL

Elevated levels of p56-Lck kinase activity were achieved in an interle ukin 2 (IL-2)-dependent cloned cytolytic T cell CTLL-2 through gene tr ansfer approaches. CTLL-2-Lck cells remained dependent on IL-2 for gro wth and survival in culture but exhibited markedly elevated, IL-2-inde pendent cytolytic activity against a variety of tumor targets. This im mune cell effector function was similar to the non-major histocompatib ility complex-restricted cytolytic activity previously described for l ymphokine activated killer (LAK) cells, and involved a cytolytic mecha nism that was independent of protein synthesis in either the T cells o r the tumor targets. Characterization of CTLL-2-Lck cells revealed mar kedly elevated levels of both the alpha (CD11a) and beta (CD18) chains of the cell adhesion molecule lymphocyte function-associated 1 (LFA-1 ) and increased binding of these T cells to a recombinant protein repr esenting the extracellular domain of the LFA-ligand, intercellular adh esion molecule 1 (ICAM-1). Antibodies to CD11a partially abrogated cyt olytic killing of tumor target cells by CTLL-2-Lck cells, suggesting t hat the upregulation in LFA protein levels potentially accounts at lea st in part for the phenotype of these T cells. Gene transfer-mediated elevations in p56-Lck kinase activity in an IL-3-dependent myeloid cel l clone 32D.3 also resulted in increased LFA-1 expression, demonstrati ng that the findings are not unique to CTLL-2 cells. In addition to up regulation of LFA-1 expression, CTLL-Lck cells also exhibited more eff icient exocytosis of cytotoxic granules upon activation with Ca2+-iono phore and phorbol ester, relative to control transfected and untransfe cted CTLL-2 cells. The findings functionally link the Lck kinase to a T cell effector pathway involved in cell-mediated cytotoxicity.