Cell-medicated cytotoxicity against ectromelia virus-infected target cells. III. Role of the H-2 gene complex.

The role of the H-2 gene complex in expression of cytotoxicity exerted by specific ectromelia-immune thymus-derived (T) cells against ectromelia-infected target cells was examined. A repertoire of inbred mouse strains (some congenic) including the H-2 haplotypes k, d, b, s, q, the recombinant H-2a(k/d) and F1 hybrids (k/b and d/b) were immunized with virus and their spleen cells tested 6 days later, at the peak of the primary response, against H-2k,H-2d and H-2b target cells. Significant specific cytotoxicity occurred only when the immune cell donors and the target cells shared all or part of the same H-2 gene complex. For example, H-2a (k/d) immune cells killed both H-2k and H-2d target cells. There was no detectable effect of the non-H-2 genetic background, H-2 public specificities, or the M-locus. Target cells infected with ectromelia virus exhibited quantitative or qualitative changes (or both) in expression of normal H-2 antigens as indicated by reduced susceptibility to killing by T cells activated against H-2 antigens in mixed lymphocyte culture. These data are consistent with the hypothesis that T cells in this system are responding to virus-induced, specific changes in antigens on infected cells which are controlled by genes in the H-2 complex; these genes seem likely to be those coding for H-2 private specificities, or genes closely linked to them.