One of the more recent associations of the murine H-2 major histocompatibility complex (MHC) with immune function has been the finding that cytotoxic T-effector cells generated by sensitization with viral-infected (1-6), chemically modified (7-9), or weak transplantation antigen-associated (10,11) syngeneic cells can efficiently lyse target cells which express the same viral, chemical, or weak antigenic agent, and which share the H-2K and/or H-2D regions of the MHC with the responding and/or stimulating cells. Furthermore, an additional contribution of a gene(s) within the H-2 complex has been demonstrated which controls immune response potential (Ir genes) in the generation of cytotoxic effector cells to trinitrophenyl (TNP)-modified self components (12,13). In such studies it was found that certain B10 congenic strains generated good cytotoxic responses to both TNP- modified H-2K and H-2D region products, whereas other B10 congenic strains exhibited preferential or exclusive reactivity against TNP-modified H-2K region products. Some of these recombinant strains differing in response potential to TNP- modified H-2D products expressed the same haplotype at the D end, but differed at the K end of H-2. The low responsiveness observed in the B10.A strain to TNP-modified H-2D(d) when compared to B10.D2 and (B10.A x B10.D2)F(1) for the same specificity, suggested a role of dominant Ir genes which map in K, I-A, I-B, I-J, and/or I-E (12, 14).

In the present report an attemnpt was made to further map within the MHC the Ir gene(s) controlling cell-mediated lympholysis (CML) to TNP-modified H-2D(d), by using recombinant mouse strains on the A and B10 backgrounds. Irrespective of the genetic background, the s and k haplotypes at the K end generated high and low cytotoxic responses, respectively, to H-2D(d)-TNP. The intermediate responder and low responder status of the A.TL and A.AL strains, respectively, indicated that a gene mapping in the K region of H-2 influences response potential. Furthermore, the differences in the levels of cytotoxicity detected in the A.TH and A.TL strains suggested an additional I region influence. Taken together these findings raise the possibility that multiple genes mapping within different regions of the MHC control the level of T-cell-mediated cytotoxicity to chemically modified autologous cells.

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