Mutations in ras genes which result in transforming gene products carrying amino acid substitutions in position 12, 13 or 61 are common in human cancer. Peptides encompassing these mutations in ras are shown to be immunogenic in both mice and humans. The potential usefulness of such peptides in cancer therapy, depends on their ability to bind to HLA molecules. We therefore stimulated T cells from healthy donors with mutated ras-derived peptides. By repeated in vitro stimulation of peripheral blood mononuclear cells, several T cells clones could be generated which recognized a p21 ras derived peptide carrying a position 12 Gly-->Arg substitution. This peptide (1-25,12 Arg) could be specifically recognized by T cells restricted by either HLA-DQ7 or -DP3. Previously, we showed that this peptide is also recognized by a T cell clone restricted by HLA-DR2. The core region of the peptide was determined to span positions 9-16 for all three HLA restriction elements, and accordingly contains the mutational hot spots in position 12 and 13. The observation that the mutant 1-25,12 Arg ras-derived peptide may contain a promiscuous epitope encompassing the Gly-->Arg mutation in position 12 indicates that lack of peptide presentation by given HLA molecules may not be a major constraint in responsiveness against ras mutations.

To characterize the T cell receptor repertoire in an immune response in which the Ia and nominal antigenic determinants are defined and limited, we have cloned and sequenced the expressed receptors from four independent, beef insulin-specific T cell lines from C57BL mice. Each of these lines responded to beef but not to the pork insulin, thus defining the nominal antigenic determinant recognized. Furthermore, each of these lines could only be presented antigen by B6 but not mutant B6.C-H-2bm12 antigen-presenting cells, thus defining the requisite Ia recognition or antigen-association site. In spite of this functional similarity in ligand specificity, each of these T cell lines was found to use different V alpha and V beta gene segments. Moreover, structural comparisons of implied protein sequences of each of these receptors showed no stretches of conserved amino acid residues that could be implicated in ligand interaction. However, the V alpha genes used by these four clones appeared considerably more homologous to each other than were their V beta genes.

restriction fine-specificity and T-cell receptor usage of T cells recognizing DQ7.Tissue Antigens 1994: 43: 266-270. 0 Munksgaard, 1994 To study the HLA restriction fine-specificity of T cells recognizing DQ7 and correlations between HLA specificity and TCR usage, we investigated five alloreactive DQ7-specific and two peptide-specific DQ7-restricted TLC.The serologically defined DQ7 specificity in caucasians encompasses two different variants: DQ-(a1 *0302,P1*0301) encoded by genes on the DR4,-DQ7 haplotype and DQ(al*O501 ,Pl*0301) encoded by genes on the DR5,DQ7 haplotype. The DQP chains (DQP1*0301) are identical, but the DQa chains differs at 10 amino acid (aa) residues in the first domain (1). Previous studies of T-cell receptor (TCR) aP+ alloreactive T-lymphocyte clones (TLC) have demonstrated T-cell recognition of DQ7 at the DR4,DQ7 haplotype [DQ(a1*0302,-Pl*0301)] (2), while others have demonstrated TLC recognizing DQ7 irrespective of whether at the DR4, DQ7 or DR5,DQ7 haplotypes; i.e. restricted by DQ(P1*0301) paired with either the DQ(a1-*0302) or the DQ(al*0501) (3).The proposed three-dimentional structure of the TCR suggests that the complementarity-determining regions (CDR) 1 and 2, encoded by the TCRV genes, interact with the a-helixes of the HLA molecules, whereas the CDR3, encoded by the V-(D)-