The Molecular Identification of Two Serologically Defined Gene Products of the Rat Major Histocompatibility Complex

Abstract

Abstract The two SD gene products of the rat major histocompatibility complex were identified by immunochemical means with rat alloantisera. WKA anti-TO antiserum contained anti-TO reactivity possibly detecting a unique private specificity for the Tokyo strain or rats, as well as some other cross-reactivity against common public specificities among ACI, Spd, LEJ, and TO. WKA anti-TO antiserum could react with 125I-labeled AgB4 preparation. The immunoprecipitates gave two peaks of radio-activity on SDS-PAGE corresponding to positions of 37,000 and 12,000 daltons, respectively, showing the basic structure of AgB antigens as described previously. These components were confirmed, by a sequential immunoprecipitation test with rabbit anti-H-2K,D and rabbit anti-HLA-A,B antiserum, to be of the rat major histocompatibility antigens. Two different SD gene products were identified by sequential immunoprecipitation tests in which 125I-labeled AgB4 preparation was first treated with WKA anti-TO antiserum and the residual supernatants were allowed to react with a test antiserum, TO anti-ACI antiserum. Pretreatment of the antigen with WKA anti-TO antiserum could not remove the antigen molecules reactive with TO anti-ACI antiserum. Conversely, pretreatment of the antigen preparation with TO anti-ACI antiserum removed concomitantly the molecules detectable by WKA anti-TO antiserum, suggesting that both molecules carry the same private and/or public specificity(ies). The two SD antigens were inherited together in backcross animals of (ACI × WKA)F1 × WKA, indicating a close linkage of the two SD loci. There was one discrepant animal out of 63 rats tested, suggesting a dissociation of the two loci.