H-2 effects on cell-cell interactions in the response to single NON-H-2 alloantigens: II. H-2 D region control of H-7.1-specific stimulator function in mixed lymphocyte culture and susceptibility to lysis by H-7.1-specific cytotoxic cells*

The relative immunogenicity of the H-7.1 alloantigen has been shown in a previous communication to be regulated by a gene in the D region of the mouse major histocompatibility (H-2) complex. The level of relative immunogenicity was inferred from survival times of H-7.1-incompatible skin grafts donated by donors with different H-2 haplotype origins of H-2D region genes. In this communication we report the results of an extension of these previous investigations into the possible role of H-2D region genes in controlling the capacity of H-7.1-incompatible lymphocytes to stimulate H-7.1-speciflc mixed lymphocyte culture proliferation and generation of cytotoxic effector cells. The results reported herein demonstrate that the H-2D genotype of H-7.1-incompatible stimulator cells determines the relative H-7.1-specific capacity of those lymphocytes to stimulate H-7.1-specific proliferation of in vivo primed responder T cells in secondary mixed lymphocyte culture. H-2Db-bearing, H-7. l-incompatible stimulators were significantly more effective in stimulating H-7.1-specific proliferation than H-2D^d-bearing stimulators. As expected, H-2D^b, H-7.1-incompatible stimulators were also more effective than H-2D^d stimulators in generating H-7.1-specific cytotoxic effector cells. Further, the susceptibility of ⁵¹Cr-labeled, H-7.1-incompatible lymphoblast targets to H-7.1-specific lysis was similarly regulated by an H-2D gene. Reciprocal H-2 restriction (F₁ cells are capable of killing only the cells bearing the immunizing cell parental H-2 haplotype) observed by other investigators for cytolysis of non-H-2-incompatible targets was not observed. H-2D^d -bearing, H-7.1-incompatible stimulators stimulated generation of cytotoxic effectors capable of detectably lysing H-2D^b but not H-2D^d -bearing, H-7.1-incompatible targets. The impact of these observations on the proposed models for H-2 restriction of non-H-2 histocornpatibility antigen-specific cytolysis is discussed.