Functional and Vβ repertoire characterization of human CD8+ T‐cell subsets with natural killer cell markers, CD56+ CD57− T cells, CD56+ CD57+ T cells and CD56− CD57+ T cells

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Abstract
We investigated the individual CD8+ populations with natural killer (NK) cell markers (NK‐type T cell); CD56 single positive (CD56)‐T cells, CD56/CD57 double positive (DP)‐T cells and CD57 single positive (CD57)‐T cells in the peripheral blood. All NK‐type T‐cell populations expressed CD122 and intermediate levels of T‐cell receptor (TCR; regular CD8+ T cells are CD122− and express high levels of TCR). The number of both DP‐T cells and CD57‐T cells, but not CD56‐T cells, gradually increased with age. All NK‐type T‐cell populations produced larger amounts of interferon‐γ than did regular CD8+ T cells after stimulation with interleukin (IL)‐2, IL‐12 and IL‐15. However, CD56‐T cells and CD57‐T cells but not DP‐T cells showed a potent antitumour cytotoxity to NK‐sensitive K562 cells, whereas only CD56‐T cells showed a potent cytotoxity to NK‐resistant Raji cells. Furthermore, although NK‐type T cells produced large amounts of soluble Fas‐ligands, their cytotoxic activities appeared to be mediated by the perforin/granzyme pathway. The oligoclonal or pauciclonal expansions of certain VβT cells were found in each NK‐type T‐cell population. The non‐variant CDR3 region(s) for the TCRβ chain(s) showed CD57‐T cells and CD56‐T cells to be derived from distinct origins, while the DP‐T cell population consisted of a mixture of the clones seen in both CD56‐T cells and CD57‐T cells. Our results suggest that CD57‐T cells and CD56‐T cells are functionally and ontogenically different populations while DP‐T cells appear to originate from both CD56‐T cells and CD57‐T cells.