Isolation and Analysis of Subpopulations of I-A^b Molecules with Monoclonal Antibodies

Abstract

Ia antigens of the mouse H-2 complex are glycoproteins containing two noncovalently associated polypeptides of 33–35,000 daltons (alpha chain) and 25–28,000 daltons (beta chain) (1,2). Two types of Ia antigens, I-A and I-E molecules, have been identified with the genes coding the A_α, A_β and E_β polypeptide chains mapping in the I-A subregion and the genes encoding the E_α chain mapping in the I-E subregion (3–5). Studies from this laboratory using monoclonal antibodies have suggested the existence of multiple I-A and I-E molecules coded by duplicated A_α, A_β and E_α genes. Sequential immunoprecipitations with two I-E monoclonal antibodies suggest that there are at least two E_β polypeptide chains and two E_α chains (6). Sequential immunoprecipitations of I-A^b molecules with monoclonal antibodies suggest that there are subpopulations of I-A^b molecules (7). In this paper, we have isolated subpopulations of I-A^b molecules from immunoadsorbent columns and analyzed these subpopulations by immunoprecipitation with a panel of monoclonal antibodies.