A new locus (H-2T) at the D end of the H-2 complex

A.TH (H-2^t2) anti-A.TL (H-2^t1) effectors, obtained after in vitro restimulation of in vivo sensitized cells, react in the CML assay not only with H-2^t1, but also with a number of other targets carrying unrelated H-2 haplotypes. The broad cross-reactivity can be explained by postulating the presence among the effectors of at least two populations of cells, one reacting with antigens controlled by the I region, and the other directed against antigens controlled by a locus at the D end, outside the H-2 complex. The existence of the two cell populations is also supported by cold-target inhibition data. The locus coding for the D-end CML antigens maps between Qa-2 and Tla. The locus is assigned the symbol H-2T. The H-2T-locus CML is seen only after in vivo presensitization, but the killing is not K/D-restricted.