Stimulation of NK-like YT cells via leukocyte function-associated antigen (LFA)-1. Possible involvement of LFA-1-associated tyrosine kinase in signal transduction after recognition of NK target cells.

The YTA-1 anti-LFA-1 alpha mAb activates protein tyrosine kinase (PTK), augments NK cytotoxicity, and induces proliferation of fresh CD3- large granular lymphocytes. We demonstrate here that LFA-1 is physically associated in the YT human NK-like cell line cells with a PTK(s) that is distinct from Src family PTKs such as Lck, Fyn, or Lyn. In vitro kinase assays revealed similar association of protein kinase activity with LFA-1 in normal CD3- large granular lymphocytes. Tyrosine phosphorylation of the proteins associated with LFA-1 drastically increased in YT cells after stimulation with NK-sensitive K562 cells but not with NK-resistant P815 cells. Furthermore, pretreatment of YT cells with TS1/22 anti-LFA-1 alpha and TS1/18 anti-LFA-1 beta mAbs abrogated not only the cytotoxicity against K562 cells but also an increase in tyrosine phosphorylation of LFA-1-associated molecules induced by K562 stimulation. These results provide biochemical evidence that the PTK(s) associated with LFA-1 is involved in the signal transduction that follows the recognition of NK target cells.