Rat antisera directed against alloimmune murine cytotoxic T lymphocytes inhibit cytotoxic T-lymphocyte and natural killer activity: Strain specificity of inhibition

Xenogeneic antisera directed against alloimmune murine peritoneal exudate lymphocytes (IPEL) inhibit, in the absence of complement, in vitro T-cell-mediated cytolysis by IPEL and, to a comparable degree, cytolysis by in vitro-sensitized splenic cytotoxic T lymphocytes. Since inhibition by rat antiserum directed against C57B1/6J (B6) IPEL was obtained with alloimmune cytotoxic T lympocytes (CTL) from several different inbred strains of divergent major histocompatibility complex (MHC) specificity, the inhibitory antibodies are not directed against idiotypic portions of the T-cell receptor. Moreover, antibodies directed against constant or variable Lyt 2,3 determinants appear not to be involved, since xenoantiserum-mediated inhibition of CTL is independent of effector cell Lyt 2,3 phenotype, and since absorption of the xenoantiserum with Lyt 2,3-positive cells failed to reduce either titer or strength of the inhibitory activity. In other studies we obtained strong inhibition, by the rat antiserum directed against IPEL, of natural killer (NK) cells. Our results support the presence on alloimmune CTL (derived by either in vivo or in vitro immunization) and NK effectors of lytic molecules or membrane components, independent of Lyt 2,3 entities.