TRIGGERING OF HUMAN NATURAL-KILLER-CELLS THROUGH CD16 INDUCES TYROSINE PHOSPHORYLATION OF THE P72(SYK) KINASE

Activation of protein tyrosine kinases (PTK) is an initial and obligatory event for the triggering of human natural killer (NK) cells to cytotoxicity. Of the different PTK detected in NK cells, only p56(lck) has previously been shown to participate in NK cell activation. Here we present evidence that another PTK, p72(Syk), is involved in activation of NK cells. Stimulation with a monoclonal antibody to the Fc gamma RIII receptor (CD16) induced an increased tyrosine phosphorylation of p72(Syk) . This phosphorylation correlated with an increased tyrosine kinase activity of p72(Syk) towards a synthetic peptide substrate. A severalfold increase in the catalytic activity of p72(Syk) was also seen after treatment of NK cells with an inhibitor of phosphotyrosine phosphatases, pervanadate. We conclude that triggering of the cytotoxic response in NK cells is associated with activation of p72(Syk).