Low doses of interleukin 2 induce bystander cell lysis by antigen-specific CD4+ inflammatory T cell clones in short-term assay.

The effect of recombinant interleukin 2 (rIL2) and interferon-gamma (IFN-gamma) on the cytolytic activity of a CD4+ class II major histocompatibility complex-ovalbumin (OVA)-specific murine clone called 5.8.6 was examined. Low doses of IL2 (0.1-1.0 U/ml) induce clone 5.8.6 to kill in an antigen-independent fashion in short-term 51Cr-release and 3H-release assays (6-12 h). Targets killed by 5.8.6 cells include P815, YAC-1 and B lymphoma cells. IFN-gamma, alone or in combination with IL2, has no effect. 5.8.6 and similar inflammatory CD4+ T cell clones have been shown to lyse bystander target cells in the presence of a specific stimulator target. We propose that killing of bystander targets by clone 5.6.8 is due to nonspecific cytolytic activity induced by the clone's own IL2 secreted in response to recognition of the specific target.