EXPRESSION OF I‐Aα^k AND ALLELIC RESTRICTION ON A_α/A_α PAIRING IN TRANSGENIC MICE

Cell surface expression of class II major histocompatibility complex encoded (la) molecules depends on association of the component α and β chain into a stable heterodimer. Studies on cell lines transfected with MHC class II genes have revealed important limitations on the assembly of haplotype‐mismatched Aα:Aβ complex. In order to study α: β chain pairing restrictions in vivo a number of lines of transgenic mice carrying the A_α^k gene were generated. The transgene was studied in the context of H‐2^b, H‐2^s, H‐2⁴, H‐2^u, H‐2^f and H‐2^v haplotypes. Initial FACS analysis of spleen and peripheral blood cells showed no A_α^k expression. Spleen cells stimulated with LPS and analysed by FACS showed A_α^k expression in three different H‐2^b strains as well as H‐2^u, but not in others. These data indicate that A_α^k can associate with A_β^b and A_α^k, but not with A_β^s,A_β^q, A_β^f, A_β^v.