Multi-gene/allele control of Mlsb of CBA/H

Festenstein originally described the Mls locus as a single dominant autosomal gene with four alleles which mapped in the 13th linkage group of chromosome 1. We subsequently presented evidence indicating that the mixed leukocyte reaction (MLR) stimulatory products of DBA/2 and CBA/J were controlled by two independently segregating Mls loci and that Mls of C3H was in fact a composite of three independently segregating loci. Recently, Mlsd of CBA/J was shown to be composed of Mlsa of AKR and a product on C3H, which was presumed to be Mlsc. Based on strain distributions, this product cannot be encoded by the Mlsc originally defined by Festenstein. In the present report, three Mls specificities of CBA/H (Mlsb) are defined. Based on the strain distribution, we postulate that these specificities are controlled by three loci, three alleles/locus, or by some combination of the preceding two possibilities.