The Expression of I-Ed Molecules in F1 Hybrid Mice Detected with Antigen-specific, I-Ed-restricted Cloned T-cell Lines

The expression of polymorphic determinants on I-E molecules is largely dependent on allelic variation in the E beta chain. We have previously analyzed the expression of Ek beta and Eb beta chains in F1 hybrid mice by a combination of techniques, and have shown that functional variation detected by the responsiveness of cloned T-cell lines specific for these molecules correlates well with serological determination of E beta expression. In the present study, we have extended our analysis to Ed beta expression in F1 hybrid mice. We show that Ed beta is relatively poorly expressed in three F1 combinations: H-2d X H-2b, H-2d X H-2s, and H-2d X H-2u. The former two crosses express E alpha chains from the H-2d parent only; when recombinant strains carrying Eb beta or Es beta and an active E alpha gene are used, Ed beta expression is significantly increased. On the other hand, H-2u mice synthesize E alpha chains; the poor expression of Ed beta chains in this F1 hybrid apparently reflects the strong preferential association of Eu beta chains with all E alpha molecules thus far analyzed. These results confirm that E beta chains compete for binding to E alpha chains and that preferential association of different allelic forms of E beta chains with E alpha chains is a generalized phenomenon. They also illustrate the importance of the rate of biosynthesis of Ia chains for cell-surface expression.