Functional and Vbeta 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

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-gamma 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 VbetaT cells were found in each NK-type T-cell population. The non-variant CDR3 region(s) for the TCRbeta 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.

Figure 1

Expression of the intermediate levels of TCRs and CD122 on NKT cells. (a) TCR levels were demonstrated after gating CD4⁺ T-cell depleted PBMC to populations of either CD56-T cells, DP-T cells, CD57-T cells or regular T cells. Arrows in histograms indicated the peak immunofluorescence level of TCR on regular CD8⁺ T cells. (b) The expressions of CD122 were demonstrated after gating PBMC to CD56⁺ αβTCR⁺, CD56⁻ αβTCR⁺, CD57⁺ αβTCR⁺ or CD57⁻ αβTCR⁺ populations.

Figure 2

IFN-γ production, sFAS-L production, and antitumour activity of various T-cell subsets of PBMC. The indicated T-cell subsets were purified by cell sorting, and 2 × 10⁵ cells from each subset were stimulated with IL-2, -12 and -15 in 96-well flat-bottom plates for 96 hr, and IFN-γ levels (a) and sFAS-L levels (b) in culture supernatants were determined by ELISA after culturing for 48 hr. The cytotoxicities of the cultured subsets against K562 cells (c) (E/T ratio was 10/1) and against Raji cells (d) (E/T ratio was 10/1) were also measured after culturing for 96 hr. All data represent the means ± SE from four independent experiments.

Figure 3

T-cell receptor β repertoires of CD56-T cells, DP-T cells CD57-T cells and regular-CD8⁺ T cells. PBMC from five individual healthy volunteers with indicated ages were stained as described in Materials and Methods and percentages (%) of VβT cells in each subset were demonstrated.