The effect of interferon treatment of targets on susceptibility to cytotoxic T-lymphocyte killing: augmentation of allogeneic killing and virus-specific killing relative to viral antigen expression.

The effect on CTL lysis of treatment of CTL targets with IFNs has been investigated. Treatment of targets for alloreactive CTL with either IFN-alpha beta or IFN-gamma markedly augmented cytotoxicity. Cold competition experiments implied that CTL recognized the same target structure on both untreated and IFN-treated cells. This augmented lysis is presumably caused by IFN increasing expression of target MHC antigens. In the case of SFV-specific lysis of SFV-infected fibroblasts, IFN-alpha beta or IFN-gamma treatment somewhat reduced CTL lysis, but less so than Ab + C lysis which was abolished at moderate IFN concentrations; in the case of SFV-infected lymphoblastoid cells, CTL lysis remained the same or was slightly increased, whilst Ab + C lysis was reduced at moderate IFN concentrations and abolished at high IFN concentration; in the case of MSV/MLV-infected fibroblasts, CTL lysis was moderately increased whilst Ab + C lysis was decreased. IFN therefore increases virus-specific CTL cytotoxicity relative to viral antigen expression.