F₁ hybrid-anti-parental H-2^b cell-mediated lympholysis: Genetic control of target antigens by the H-2D region

The immunogenetic specificity of (C57BL/6 x DBA/2)F₁ anti-parental C57BL/6 cytotoxic T lymphocytes (CTL) induced in primary mixed spleen cell cultures was determined in direct lytic and competitive inhibition assays. A large panel of peritoneal exudate cells (PEC) bearing nonrecombinant and recombinant H-2-Tla haplotypes was the source of target and inhibitor cells. All PEC of H-2(b), H-2(bc),H-2(j), and H-2(ja) types, irrespective of background genetic constitution, were as susceptible to direct lysis as C57BL/6 PEC, but PEC of H-2(a), H-2(d), H-2(k), H-2(q), H-2(s), and H-2(u) types were not. The possible involvement of the Tla region in controlling target antigens was excluded by testing PEC obtained from 4 H-2/Tla or intra-Tla recombinant mouse strains. The genes controlling target antigens were mapped to the D region with the aid of 9 intra-H-2 recombinants; for target PEC to be lysed it was necessary and sufficient that D^b antigens be part of the H-2 phenotype. These results were confirmed by competitive inhibition assays. Resident peritoneal cells not exposed to fetal bovine serum were also lysed by F₁ anti-parental H-2^b CTL, a demonstration that target antigens are expressed on normal cells.