Monoclonal antibodies H9-15.4 and H39-459 were derived from an A.TH anti-A.TL immunization. Antibodies H9-15.4 and H39-459 were found to be directed against the I-Ek molecule with positive reactions against B10.A (AkEk) and B10.S(9R) (AsEk) but not B10.A(4R) (AkEb). The monoclonal antibodies were also found to react with the b and q haplotypes, which do not express an I-E molecule. Sequential precipitation analysis showed that in the b haplotype, H9-15.4 and H39-459 react with the I-Ab molecule. These results showed that H9-15.4 and H39-459 recognize determinants shared by 1-Ek and I-Ab molecules, suggesting that I-A and I-E molecules may have a common evolutionary origin, possibly through gene duplication. Sequential immunoprecipitation analysis of l-Ab molecules precipitated by H9-15.4 and H39-459 also suggested that these monoclonal antibodies recognize subsets of I-Ab molecules. Pretreatment with the 17-227 monoclonal anti-1-Ab antibody (Ia.15) had no effect on I-Ab molecules precipitated by H9-15.4 and H39-459. Also, pretreatment with H9-15.4 and H39-459 had no effect on I-Ab molecules immunoprecipitated by 17-227. Also H9-15.4 and H39-459 only partially cleared Ia molecules immunoprecipitated by each other. These results suggest that 17-227, H9-15.4, and H39-459 detect a minimum of four subsets of l-Ab molecules. To account for these observations, it is proposed that during evolution of the mouse H-2 complex, in addition to gene duplication of ancestral gene(s) to yield the genes encoding EαAα, Aβ, and Eβ polypeptide chains, further gene duplication occurred, forming multiple copies of genes encoding each Ia polypeptide chain.
ASJC Scopus subject areas