Characterization of conserved CDR3 sequence of TCR alpha- and beta-chain genes in peripheral blood T-cells from patients with diffuse large B-cell lymphoma.

T-cell immunodeficiency is a common feature in cancer patients, but clonally expanded T cells which were considered to have the specific anti-tumor cytotoxicity can be identified in most cancer patients, including those with hematological malignancies. We previously reported that there were skewed usages of T-cell receptor (TCR) Valpha and TCR Vbeta subfamily in clonally expanded T cells in the peripheral blood (PB) of patients with diffuse large B-cell lymphoma (DLBCL). In order to investigate the characteristics of the complementarity determining region 3 (CDR3) of TCR alpha- and beta-chain genes in clonally expanded T cells, the sequences of TCR-CDR3 region of clonally expanded TCR Valpha and TCR Vbeta subfamily T cells were analyzed. Conserved amino acid motifs of TCR-CDR3 region were identified in different clonally expanded T cells. RSxYNTDKLI, SxGG, GGS, and DSxY motifs were found in the TCR Valpha subfamily T-cell clones, while SxGTG, SRG, and GTxD motifs existed in the TCR Vbeta subfamily T-cell clones. Moreover, the TCR harboring conserved motif in CDR3 region of some T-cell clones had high homology in the three-dimensional spatial structures. These findings revealed the mono/oligoclonally expanded T cells were derived from the stimulation of some antigens in the PB of patients with DLBCL, and may be recognizing an identical antigenic epitope.