Competition among class II major histocompatibility molecules for presentation of tyrosine‐azobenzenearsonate occurs in vivo and in vitro

Abstract

We have compared by functional assays the relative preference among Ia molecules for their ability to present tyrosine-azobenzenearsonate (ABA-Tyr) to T cells. Immunization of B10.BR mice (IAk, IEk) with ABA-Tyr resulted in the induction of IAk-restricted T cells only. Immunization of B10.A(5R) mice (IAb, IEb/k) gave only IEb/k-restricted T cell clones even though IAb-restricted responses could be induced in C57BL/6 mice (IAb). These results indicated that IAk was preferred over IEk and IEb/k was preferred over IAb for presentation of ABA-Tyr. A comparison between IAk and IEb/k made by immunizing [B10.BR x B10.A(5R)]F1 mice (IAk, IEk, IAb, IEb/k), showed that IEb/k was favored over IAk. No IAb- or IEk-restricted response was seen. Further attempts were made to compare Ia preference for ABA-Tyr presentation by competitive inhibition assays. It could be shown that the presence of IEb/k molecules on an accessory cell interfered with the ability of IAb molecules on the same cell to present ABA-Tyr to an IAb-restricted T cell clone by direct competition. Such a competition was not observed between IAk and IEk. Finally, it could be shown that addition of ABA-Tyr inhibited the presentation of moth cytochrome-c peptide (81-103) by IEb/k but did not influence its presentation by IEk. From these functional studies we suggest that the binding affinity of ABA-Tyr with the Ia molecules will fall in the order: IEb/k greater than IAk greater than IAb greater than IEk.