Signal transduction via phosphorylated adhesion molecule, LFA-1 beta (CD18), is increased by culture of natural killer cells with IL-2 in the generation of lymphokine-activated killer cells.

It is well known that IL-2 stimulates natural killer (NK) cells to express lymphokine activated killer (LAK) activity and that this stimulation prompts the acquisition of the ability to lyse previously insensitive target cells. The possible role of adhesion molecules in the IL-2 activation process was probed by focussing on a lymphocyte function-associated antigen (LFA)-1-dependent model system. A mAb to the LFA-1 beta chain abrogated LAK activity, but only moderately suppressed NK activity, suggesting a differential role for LFA-1 beta in LAK compared with NK mediated lysis. Orthophosphate labeling demonstrated that the LFA-1 beta chain was strongly phosphorylated in LAK but not NK cells; in contrast, the alpha chain was phosphorylated similarly in both effector cell types. At least a portion of the phosphorylation of the beta chain was on tyrosine residues, as shown by Western blotting with anti-phosphotyrosine antibody of LFA-1 beta immunoprecipitates. Crosslinking of the LFA-1 beta chain with plastic-adhered antibody stimulated Ca(2+)-dependent release of cytoplasmic lytic granules and induced phosphatidyl inositol turnover in LAK but not NK cells. We conclude that the IL-2-induced phosphorylation of the beta chain of the LFA-1 adhesion molecule in LAK cells and associated alteration in signal transduction may be important in the stimulation of LAK cell activity in NK cells.