No abstract

Sequential immunoprecipitation and isoelectric focusing analyses with monoclonal I-E-specific antibodies presented in this paper indicate the existence of multiple I-E molecules. In sequential immunoprecipitations with 13-4 (anti-Ia.7) and 17-3-3 (anti-Ia.22) monoclonal antibodies, 17-3-3 only partially cleared I-E molecules immunoprecipitated by 13-4. Similarly, 13-4 monoclonal antibody only partially cleared I-E molecules precipitated by 17-3-3 monoclonal antibody. These results suggested a minimum of three I-E molecules. One I-E molecule expresses both 13-4 and 17-3-3 determinants, a second I-E molecule expresses only 17-3-3 determinants, and a third I-E molecule expresses only 13-4 determinants. Isoelectric focusing analyses of I-E molecules immunoprecipitated by 13-4 and 17-3-3 showed differences in both Ae beta polypeptide chains and E alpha polypeptide chains. The sequential immunoprecipitation and isoelectric focusing analyses presented in this paper can be explained by a model in which there are at least two separate Ae genes being encoded within the I-A subregion and two separate E alpha genes being encoded within the I-E subregion. The 17-3-3 monoclonal antibody would recognize a determinant on only one of two Ae beta polypeptide chains and the 13-4 monoclonal antibody would recognize a determinant on only one of two E alpha polypeptide chains.

Ia specificity 22 is expressed on a hybrid I-E molecule formed by the association of a beta chain (Ae) coded for by the I-A subregion and an alpha chain (E alpha) encoded by the I-E subregion. Ia.22 can be generated by the complementation of Ab, Ak, As, Ar, with Ed, Ek, Ep, Er, Ew3, Eu, Ev but Eb, Ef, Eq, and Es. With the exception of H-2p which does not complement with As to generate Ia.22, all Ia. 7-positive (I-E) haplotypes can provide the permissive E alpha allele. It is postulated that Ia.22 is a combinatorial Ia determinant generated by the association of the alpha and beta chains. These determinants are probably involved in the immune recognition of antigens under dual Ir-gene control.

Recombinant D2.Gd (KdAdBbJbEbCbSbDb) was derived from parental strains B6 (H-2b) and DBA/2 H-2d). Recent peptide studies and 2-D electrophoresis studies from other laboratories have shown that the Aed (E beta) chain of D2.GD is structurally different from the parental-derived chain. An antiserum (D2.GD X A. TFR5)F1 anti-DBA/2 was produced that detects an Ia specificity (Ia.50) in the I-E molecule formed by the parent Aed chain and lacking in the I-E molecule formed by the variant Aed. chain. The variant Ae chain could have derived either from a mutational event or an intracistronic cross-over.