Shared structural motifs in TCR of glycopeptide-recognizing T cell hybridomas.

The TCR structure of T cell hybridomas recognizing a tumor glycan-defined epitope has been studied using reverse transcriptase-PCR and gene sequencing. The hybridomas had been raised against a glycopeptide, T-72(Tn), consisting of the mouse hemoglobin-derived decapeptide Hb(67-76), O-glycoslated in position 72 with alpha-D-GalNAc. The glycan-specific hybridomas varied widely in their use of V alpha genes although V alpha 4 was predominant, being present in one third of them. The V beta gene usage was more restricted and dominated by V beta 1 and v beta 15. There was no correlation between V alpha and V beta usage and antigen fine specificity of the hybridomas. The overall amino acid composition of the complementarity-determining region (CDR) 3 of the hybridomas was dominated by small polar residues such as Gly, Asn, Ser, Glu and Ala, amino acids reported in the literature to be frequent in glycan-recognizing proteins. Furthermore, the CDR3 of most hybridomas also contained an aromatic residue with preference for Tyr. A few of the hybridomas raised against the T-72(Tn) glycopeptide were peptide specific, i.e. they responded to the unglycosylated peptide only. The amino acid usage of their CDR3 regions was not radically different from that of the glycopeptide specific hybridomas. They also preferentially used V alpha 4, However, V beta 4 and V beta 8 were the dominating beta chains.