THE ORIGIN OF THE AUTOIMMUNE DISEASE-RESISTANT LER RAT - AN OUTCROSS BETWEEN THE BUFFALO AND AUTOIMMUNE DISEASE-PRONE LEWIS INBRED RAT STRAINS

The Lewis (LEW) rat strain is highly susceptible to a large number of experimentally induced inflammatory and autoimmune diseases. The Lewis resistant (LER) rat strain, which reportedly arose as a spontaneous m utation in a closed colony of LEW rats, is resistant to many of these disorders. The mechanism of resistance is not yet clear. We report the analysis of 19 simple dinucleotide repeat polymorphisms in 13 rat str ains including the LEW/N and LER/N rat strains. The LEW/N and LER/N al leles were the same in only 42% of cases. For all of the other polymor phisms, the LER/N and Buffalo (BUF/N) rat strain alleles were identica l. These data provide evidence that the LER strain did not arise as a spontaneous mutation in the LEW strain but is the result of an outcros s between the LEW and BUF rat strains. The LER rat strain is now a rec ombinant inbred rat strain. This information should facilitate the gen etic analysis of the loci responsible for resistance to experimental a utoimmune disease in the LER rat.