The effect of transfected MHC class I genes on sensitivity to natural killer cells.

To test the hypothesis that major histocompatibility complex (MHC) molecules protect target cells from lysis by natural killer cells (NKC), we transfected the MHC- B16 melanoma line F10 with the class I genes encoding Dd, Kb, and Kk. Only low levels of Dd expression could be obtained and there was no protection against NKC. By contrast, Kb and Kk transfectants were obtained which displayed significant resistance to NKC, and with the latter transfectants resistance was clearly related to the level of transgene expression. Various mutants of the F10 line with altered patterns of MHC expression were also obtained. These mutant lines provided evidence that (i) the Db molecule is also capable of inducing resistance to NKC and (ii) high MHC class I expression does not by itself guarantee lowered susceptibility to NKC.