Qed-1--a target for unrestricted killing by T cells.

Two prototype target determinants for unrestricted killing by T cells are defined: Qed-1a, detected on B6.Tlaa targets by C3H/HeJ lymphocytes primed in vivo and restimulated in vitro by B10.BR spleen cells; and Qed-1b, detected on C57BL/6J lymphocytes by B10.BR anti-C3H/HeJ effector cells generated in the same manner. Other mouse strains can be typed for Qed-1 by the ability of their lymphocytes to inhibit one of these lytic reactions. Of 55 inbred strains, 52 expressed either Qed-1a or Qed-1b, which thus behaved as products of alleles of a single locus, Qed-1. The remaining three strains, all H-2r, did not compete against specific lysis of Qed-1a, but inhibited Qed-1b-specific lysis only in part; it is proposed that these strains carry a third allele or haploype, Qed-1c. The Qed-1 locus was mapped distal to Qa-2. Qed-1b was found on both normal and mitogen-activated lymphocytes and did not appear confined to any lymphoid subpopulation. Cytotoxic responses, not restricted by H-2 and specific for antigens controlled by the Tla region, could be induced in several combinations of H-2-identical strains differing at Qed-1. Cells of some strains, like B10.BR, NZB, and SWR, responded directly in culture, even without priming in vivo.