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 obligat ory event for the triggering of human natural killer (NK) cells to cyt otoxicity. Of the different PTK detected in NK cells, only p56(lck) ha s 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 R III receptor (CD16) induced an increased tyrosine phosphorylation of p 72(Syk) . This phosphorylation correlated with an increased tyrosine k inase activity of p72(Syk) towards a synthetic peptide substrate. A se veralfold increase in the catalytic activity of p72(Syk) was also seen after treatment of NK cells with an inhibitor of phosphotyrosine phos phatases, pervanadate. We conclude that triggering of the cytotoxic re sponse in NK cells is associated with activation of p72(Syk).