Natural killer (NK)-like cytotoxic activity of allospecific T cell receptor-gamma,delta+ T cell clones. Distinct receptor-ligand interactions mediate NK-like and allospecific cytotoxicity.

We recently generated a series of human alloantigen-specific, CD3+,TCR-gamma,delta+ clones by stimulating CD3+,CD4-,CD8- T cells from normal individuals with allogeneic lymphoblastoid cell lines (LCL). As reported previously, these clones display cytotoxic activity against their specific stimulators but not against irrelevant LCL. Further studies of these and other TCR-gamma,delta+ clones, described in this report, indicate that most but not all of these clones express the NK cell associated marker, NKH-1 or Leu-19, and kill NK-sensitive targets such as the K562 and Molt 4 lines, but not an irrelevant LCL or NK-resistant line, Raji. TCR-gamma,delta+ clones which lacked expression of Leu-19 lysed their allospecific targets but had no detectable NK activity. The allospecific cytotoxicity of Leu-19+ and Leu-19- clones was inhibited by mAb to CD3 or the TCR delta-chain. In contrast, the NK-like activity of the Leu-19+ clones was enhanced by these antibodies over a wide range of antibody concentration. Although mAb to LFA-1 markedly inhibited both the allospecific and NK-like activity of these clones, an HLA class I framework specific mAb (W6/32) had no effect on NK-like cytolysis but did inhibit allospecific killing, suggesting that the target structures on the surface of allospecific and NK-sensitive cells are distinct. The receptors utilized by the TCR-gamma,delta+ clones to recognize NK-sensitive and allospecific targets are also distinct, since killing of NK-sensitive targets was blocked by the presence of cold (unlabeled) NK-sensitive cells but not by cold allospecific targets, whereas allospecific cytolysis was inhibited by cold allospecific targets but not by NK-sensitive cells. We conclude that some CD3+,TCR-gamma,delta+ clones exhibit NK-like as well as allospecific killing and that these two activities are mediated by distinct receptor-ligand interactions.