Lack of gene complementation prevents expression of I-Ek in recombinant A.TFR5

The I-E molecule is produced by complementation of genes in I-A (A(e)) and I-E (E(α)). Ia specificities 22 and 23 are generated by the hybrid molecule, whereas Ia.7 is an allotypic determinant presumably on the α-chain of the I-E molecule. Recombinant A.TFR5 (A(f)E(k)) lacks detectable I-E molecule since A(f) and E(k) cannot complement. In a cross between A.TFR5 and B10.A(4R) (A(k)E(b)), A(k)(e) and E(k)(α) can succesfully complement to express the I-E(k) molecule on the cell surface of the heterozygote. Haplotypes H-2(b) and H-2(s) can also provide the permissive A(b)(e) and A(s)(e) for complementation with E(k)(α) of A.TFR5.