Isotypic and allotypic variation of human class II histocompatibility antigen α -chain genes

DNA sequences of four human class II histocompatibility antigen α chain DNA sequences (derived from cDNA and genomic clones representing DC1 α , DC4 α , DX α and SB α ) are presented and compared to DR α and to mouse I-A α and I-E α sequences. These data suggest possible mechanisms for the generation of polymorphism and the evolution of the DR, DC and SB families.