VARIANTS OF Mta, THE MOUSE MATERNALLY TRANSMITTED ANTIGEN, DETERMINED BY THREE ALLELES OF THE EXTRACHROMOSOMAL GENE Mtf

Two new forms of Mta, the maternally transmitted antigen of the mouse, were defined by cytotoxic T lymphocytes. One is found in laboratory mice carrying the β allele of the maternally transmitted factor, Mtf, which were previously thought to be Mta‐negative. The other is associated with a new allele, Mtf^γ, and is found in wild mice from Toulouse. Like the common form of Mta, determined by the extrachromosomal Mrf^α, the new forms are also dependent on the α allele of Hmt, a chromosomal gene linked to H‐2. and are associated with β₂‐microglobulin. Killers could be raised in all six combinations of a, β, and γ mice, showing that each form of Mtf determines a distinct (set of) epitope(s). We propose that the product of the Hmt gene, a class I MHC antigen, presents a peptide derived from a mitochondrial gene product on the cell surface and thereby creates the target antigen, Mta.