Physical and Epitope Analysis of a Recombinant Human T-Cell Receptor Vα/Vβ Construct Support the Similarity to Immunoglobulin

The genetic organization and protein structure of T-cell receptors (TCR) and immunoglobulins (Ig) are remarkably similar. Through recombinant, physical, and peptide-based immunological studies we demonstrated that rabbit antisera generated against a recombinant single-chain TCR (scTCR) react with defined peptide epitopes of their constituent TCR α and β chains. These antisera cross-react with the λ light-chain Mcg as well as with peptides duplicating its covalent structure. Conversely, rabbit antisera generated to human λ light chains cross-reacted with the recombinant scTCR. Rabbit anti-λ antibodies purified on an scTCR affinity column bound to T-cell lines and to T and B lymphocytes from peripheral blood. Circular dichroism analysis demonstrated plots characteristic of β-sheets for both Mcg and recombinant scTCR. Antisera directed against TCR α-chain synthetic peptides reacted with scTCR, Mcg λ light-chain protein, synthetic peptides from regions of sequence homology in β-chains, and Mcg. Based upon this homology and the serological cross-reactions which reflect conformational determinants, we suggest that the Vα/Vβ antigen-binding domain of this particular monoclonal scTCR construct is substantially similar to the conformational structure of λ light chains.