Identification of a new CML target antigen controlled by a gene associated with the Qa-2 locus

BALB/cBy anti-BALB/cJ spleen cells were tested in a secondary cellmediated lympholysis assay. The effector cells generated displayed a positive cytotoxic effect against Con A lymphoblasts from only those strains that were typed serologically as having the Qa-2^a allele. Confirmation that the target antigen is controlled by a locus closely associated with or identical to Qa-2 was obtained by the findings that target cells from B6.K2 (Qa-2^a, Qa-3^a) mice were lysed by the effector cells, while those from the Qa-2, 3 congenic strain B6.K1 (Qa-2^b, Qa-3^b) were not. The fact that target cells from a Qa-2-positive/Qa-3-negative strain (DBA/1, Qa-2^ai, Qa-3^b) were killed indicates that the target antigen is controlled, at least in part, by the Qa-2 locus, not the Qa-3.There is no observed H-2 genetic restriction for this cytotoxic effect, since target cells which have the Qa-2^a allele but differ from the stimulator cells at the H-2K, D, and I regions were lysed efficiently.