Distinct effects of interferon-γ and MHC class I surface antigen levels on resistance of the K562 tumor cell line to natural killer-mediated lysis

Various investigators have examined the relationship between tumor cell susceptibility to natural killer (NK) cell lysis and the expression of HLA class I antigens on the tumor cell. There is controversy as to whether or not an inverse relationship exists, and if so, the basis of the relationship between these two phenomena remains undefined. To address these questions, the genomic clones for two HLA antigens were transfected into the erythroleukemia cell line K562, a cell line that is used as the standard to assess human NK and major histocompatibility complex (MHC) nonrestricted cytolysis. Susceptibility to NK lysis was not affected by the de novo expression of HLA antigens on the K562 after DNA mediated gene transfer. Interferon-γ (IFN-γ) treatment of K562 induced levels of MHC class I antigen surface expression comparable to those found on the transfected cells; however, the IFN-γ-treated cells were resistant to NK lysis. When very high levels of surface HLA antigens were induced on the transfectants, a potential effect of class I MHC expression on K562 lysis could be discerned that was distinct from the resistance to NK lysis induced by IFN-γ treatment.