Evolutionary relationships between the t and H-2 haplotypes in the house mouse

Thirty-three mouse strains carrying t haplotypes were typed with a large battery of monoclonal and polyclonal antibodies specific for class I and class II antigens controlled by the H-2 complex. Among these t haplotypes were representatives of the six complementation groups defined previously and of eight new groups defined by us recently. The typing resulted in the identification of the H-2 haplotypes of these strains and of their alleles at K, D, A, and E loci. Nineteen of the 33 strains proved to carry a mutation that prevents the expression of the E molecule on the cell surface. All H-2 haplotypes of the t strains are related in terms of sharing certain antigenic determinants, most of which have not, as yet, been found in inbred strains or in wild mice that do not carry t haplotypes. According to the degree of serological relatedness, the haplotypes can be arranged into a pedigree presumably reflecting the evolutionary history of the t chromosomes. The ancestral t chromosome from which the 33 chromosomes derive was presumably present in the mouse population before the divergence of the Mus musculus and Mus domesticus species. The E° mutation, too, is apparently ancient because it occurs in different branches of the evolutionary tree.