Allospecific cytolytic T lymphocytes recognize conformational determinants on hybrid mouse transplantation antigens.

Abstract

Alloreactive cytolytic T cell (CTL) lines and clones have been used to identify the sites of polymorphism of antigens of the major histocompatibility complex (MHC). Specific CTL were generated against wild-type H-2b products by cells from H-2b mutant mice that had one or a few amino acid changes in either the alpha 1 or alpha 2 domains of the Kb or Db class I molecules. These CTL populations, which might be expected to react with determinants expressed on single MHC domains, were examined for lytic activity on L cells expressing newly constructed hybrid class I molecules. Transformed cell lines expressing native class I molecules or hybrid class I molecules in which the alpha 1 and alpha 2 domains of H-2Kb had been substituted by those domains of H-2Db were lysed by H-2Db-specific CTL. Similarly, all H-2Kb-specific CTL recognized hybrid molecules in which the alpha 1 and alpha 2 domains of H-2Kb were inserted into the H-2Db molecule. In contrast, exchange of the alpha 1 domains of H-2Kb and H-2Db resulted in a total loss of recognition by Kb and Db-specific CTL. These results suggest that the allodeterminants recognized by H-2 mutant CTL are influenced by interactions between the alpha 1 and alpha 2 domains, findings similar to those seen using conventional alloreactive T cells (11). These results were compared to the binding of alloreactive mAbs, including 5 new mAbs specific for the Kb molecules. Finally, it was shown that primary and secondary CTL responses could be generated by direct sensitization against hybrid class I molecules, demonstrating that these molecules express neoantigenic determinants recognized by alloreactive CTL.

Structure and function of three novel MHC class I antigens derived from a C3H ultraviolet-induced fibrosarcoma.

“…The three antigens share both public and private class I antigenic determinants, and most of the antigenic differences that have been observed among these molecules appear to correlate with discrete sequence substitutions. Previously, studies involving the serological characterization of exon-shuffled class I gene products have succeeded in localizing the structures recognized by several different allospecific mAb to individual protein domains (21,(34)(35)(36)(37) . Unfortunately, attempts to correlate such serological determinants with specific sets of amino acids have been complicated by the comparison of class I products that differ at multiple amino acid residues (38) .…”

“…Conformational interactions between class I domains have been implicated in previous studies involving the H-2K b series of class I mutants (40,41) where one to three amino acid changes in either the al or a2 domains usually result in the loss of most of the CTL epitopes . Further evidence for conformational interactions and the requirement for domain compatibility comes from studies involving the shuffling of exons that encode the al and a2 domains of class I molecules (34)(35)(36). In these studies it was found that virtually all of the CTL epitopes characteristic of the native molecules are absent from the hybrid molecules.…”

“…Detailed study of the structural bases of these conformational interactions might be uniquely accessible in the 1591/H-2Ld system for several reasons: (a) the structural differences that exist between A149, A166, and H-2Ld are quite discrete and can be easily manipulated by oligonucleotide directed mutagenesis; (b) all three antigens seem able to evoke a CTL response ; (c) A149 and A166 each crossreact to some extent with H-2Ld with respect to both CTL and serological reagents ; (d) discrete changes in crossreactivity will probably be observed after in vitro mutagenesis; and (e) H-2Ld has already been extensively characterized as a T cell target (17,18,35).…”

New family of exon-shuffled recombinant genes reveals extensive interdomain interactions in class I histocompatibility antigens and identifies residues involved.

“…The two membrane-distal domains, N and C1, are the most important for the immunological function of the class I antigens . The sites within class I molecules responsible for recognition by both monoclonal antibodies (mAbs) and CTLs have been partially localized and shown to predominantly reside in these two domains (5)(6)(7)(8)(9)(10)(11)(12) . Much of the localization of mAb and CTL epitopes has used hybrid class I molecules produced by the expression in mouse L cells of recombinant genes in which the exons encoding the individual external domains have been exchanged (5)(6)(7)(8)(9)(10)(11)(12) .…”

Idiotypic Manipulation of the Immune Response to Transplantation Antigens

“…The difference between the effects of treatment on the T-and B-cell compartments could have a variety of explanations. It could be due to a difference in the receptor idiotypes expressed (since different receptor gene pools are used), to a difference in activation requirements, or to the selective recognition of different epitopes on the same MHC antigens by B cells and T cells, a suggestion supported by analysis of T-cell lines and clones specific for a panel of in vitro derived H-2K'' mutants (Bluestone et al 1985). In light of these results, it is indeed difficult to explain the basis of earlier findings indicating significant idiotype sharing between T and B cells, with dramatic implications for transplantation.…”