Variable synthesis and expression of E alpha and Ae (E beta) Ia polypeptide chains in mice of different H-2 haplotypes.

The genetic and molecular requirements for cell-surface expression of Ia antigens precipitated by anti-I-E subregion sera have been examined. Inbred mice f the d, k, p, and r haplotypes synthesize and express on their lymphocytes the two I-region products normally found in anti-I-E-subregion immunoprecipitates, E alpha and Ae (E beta). Cells from mice of the b and s haplotypes fail to synthesize E alpha chains but do synthesize Ae chains, which remain in the cytoplasm as partially glycosylated precursors. Cells of the f and q haplotypes fail to synthesize either the Ae or E alpha polypeptide chains, as shown by both genetic complementation tests and analyses of total cell proteins by two-dimensional polyacrylamide gel electrophoresis. The patterns of expression of the intact E alpha: Ae complex are consistent with the theory that both the Ae and E alpha polypeptide chains must be present in the cells for either chain to be expressed in normal amounts on the cell surface. The implications of these observations for the genetics of I-region-controlled functions are discussed.