NEW I SUBREGION (I-J) MARKED BY A LOCUS (IA-4) CONTROLLING SURFACE DETERMINANTS ON SUPPRESSOR T-LYMPHOCYTES

In an accompanying publication it was shown that a subpopulation of [mouse] T[thymus-derived]-lymphocytes, which includes allotype suppressor T cells, selectively expresses I[immune]-region determinants. In this report, it was shown that these determinants are controlled by a new locus, Ia-4. Unlike the classically defined Ia [immune response associated] antigens, they are not found on B[bone marrow-derived] lymphocytes. Antibody against Ia-4 determinants cannot be detected by conventional dye exclusion cytotoxicity assays, suggesting that they are present on a small subpopulation (less than 10%) of peripheral T[thymus-derived-] lymphocytes. The Ia-4 locus marks a new I subregion, provisionally designated I-J. This chromosomal segment is defined by the crossover positions in strains B10.A(5R) (K-end boundary) and B10.HTT (D-end boundary), and maps between the I-B and I-C subregions.