Hybrid (combinatorial) Ia specificities: Gene complementations to generate Ia.22

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) encoded by the I-E subregion. Ia.22 can be generated by the complementation of A ^b , A ^k A ^s , A ^r with E ^d , E ^k , E ^vp , E ^r , E ^w3 , E ^u , E ^v but not E ^b , E ^f , E ^q , and E ^s . With the exception of H-2 ^p which does not complement with A ^s to generate Ia.22, all Ia.7-positive (I-E) haplotypes can provide the permissive E 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.