Modulation of NK-target cell interaction by a monoclonal antibody to K562 cells

In order to identify the target cell recognition molecules involved in the interaction between natural killer (NK) cells and target cells, we have generated monoclonal antibodies to K562, NK-sensitive target cells. After screening by FACScan for the reactivity to K562, one monoclonal antibody (mAb), 4A60, was selected. MAb 4A60 was found to inhibit the proliferation of NK cells induced by IL-2 and K562 cells. However, this monoclonal antibody could not significantly block the conjugate formation between NK and target cells. Moreover, mAb 4A60 only slightly inhibited the cytotoxicity of NK cells induced by IL-2. Protein analysis showed that mAb 4A60 recognized a 53- kDa protein of K562 cells. Taken together, these data suggest that mAb 4A60 inhibits the proliferation of NK cells induced by IL-2 and target cells, and the 53-kDa protein, a tentative ligand of this mAb of K562, may be involved in this process.