Broad interspecies cross-reactions of anti-Ia murine alloantibodies.

Interspecies cross-reactive antibodies were detected in a mouse alloantiserum, A.TH anti-A. TL raised against products of the I region genes of the H-2 complex. The cross-reactions were found to extend not only to all mammalian species tested but even to avian and amphibian species. Genetic mapping studies of the cross-reactive antibodies in the mouse indicated that the cross-reaction in all cases were attributable to the antibodies to the I-E subregion gene product, i.e. alpha-chain of the I-E molecule. These results probably indicate that the cross-reactive genes are the homologues of mouse I-E gene and share the common ancestral origin. Possible basis for such unusual interspecies cross-reactions of anti-Ia alloantibodies will be discussed.