Predominant Role of T Cell Receptor (TCR)-α Chain in Forming Preimmune TCR Repertoire Revealed by Clonal TCR Reconstitution System

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Abstract
The CDR3 regions of T cell receptor (TCR)-α and -β chains play central roles in the recognition of antigen (Ag)-MHC complex. TCR repertoire is created on the basis of Ag recognition specificity by CDR3s. To analyze the potential spectrum of TCR-α and -β to exhibit Ag specificity and generate TCR repertoire, we established hundreds of TCR transfectants bearing a single TCR-α or -β chain derived from a cytotoxic T cell (CTL) clone, RT-1, specific for HIVgp160 peptide, and randomly picked up TCR-β or -α chains. Surprisingly, one-third of such TCR-β containing random CDR3β from naive T cells of normal mice could reconstitute the antigen-reactive TCR coupling with RT-1 TCR-α. A similar dominant function of TCR-α in forming Ag-specific TCR, though low-frequency, was obtained for lymphocytic choriomeningitis virus–specific TCR. Subsequently, we generated TCR-α and/or -β transgenic (Tg) mice specific for HIVgp160 peptide, and analyzed the TCR repertoire of Ag-specific CTLs. Similar to the results from TCR reconstitution, TCR-α Tg generated CTLs with heterogeneous TCR-β, whereas TCR-β Tg-induced CTLs bearing a single TCR-α. These findings of Ag recognition with minimum involvement of CDR3β expand our understanding regarding the flexibility of the spectrum of TCR and suggest a predominant role of TCR-α chain in determining the preimmune repertoire of Ag-specific TCR.