Receptor-induced death in human natural killer cells: involvement of CD16

Propriocidal regulation of T cells refers to apoptosis induced by interleukin 2 (IL-2) activation with subsequent antigen receptor stimulation. We examined whether natural killer (NK) cells exhibited cytokine- and ligand-induced death similar to activated T cells. Peripheral NK cells were examined for ligand-induced death using antibodies to surface moieties (CD2, CD3, CD8, CD16, CD56), with and without prior activation of IL-2. Only those NK cells stimulated first with IL-2 and then with CD16 exhibited ligand-induced death; none of the other antibody stimuli induced this phenomenon. Next we examined various cytokines (IL-2, IL-4, IL-6, IL-7, IL-12, IL-13, interferon alpha and gamma) that can activate NK cells and determined if CD16- induced killing occurred. Only IL-2 and IL-12 induced NK cell death after occupancy of this receptor by aggregated immunoglobulin or by cross-linking with antireceptor antibody. The CD16-induced death was inhibited by herbimycin A, indicating that cell death was dependent upon protein tyrosine kinases. Identical to T cells, the form of cell death for NK cells was demonstrated to be receptor-induced apoptosis. Overall these data indicate that highly activated NK cells mediate ligand-induced apoptosis via signaling molecules like CD16. Whereas the propriocidal regulation of T cells is antigen specific, this is not the case for NK cells due to the nature of the receptor. The clinical implications of this finding are considered.