The identification and mapping of a second class I locus in the major histocompatibility complex of the rat.

A combined genetic, serologic, and biochemical study has demonstrated the existence of a second locus, RT1.E, that codes for class I antigens in the major histocompatibility complex (MHC) of the rat, and has mapped it relative to the other loci in the MHC. The evidence was obtained with the use of two laboratory-derived recombinants, r10 and r11, and the congenic strains DA.1I and BN.1I. Antibodies raised against the i haplotype (RT1.AnBa) in strain combinations that were matched for their RT1.A and RT1.B loci and in the BY1 and anti-r11 strain combination, in which the RT1.A and RT1.B loci and many of the non-MHC genes were matched, reacted with red blood cells and lymphocytes carrying the u haplotype. Immunoprecipitation showed that these antisera reacted specifically with a component of red blood cell membranes having a m.w. of 45,000. Mapping studies place the genes in the rat MHC in the order RT1.ABE; hence, the organization of the MHC in the rat appears to be similar to that of the mouse.