Systematic characterization of human CD8(+) T cells with natural killer cell markers in comparison with natural killer cells and normal CD8(+) T cells

We investigated the function of CD56(+) CD8(+) T cells (CD56(+) T cells) an d CD56(-) CD57(+) CD8(+) T cells (CD57(+) T cells; natural killer (NK)-type T cells) and compared them with those of normal CD56(-) CD57(-) CD8(+) T c ells (CD8(+) T cells) and CD56(+) NK cells from healthy volunteers. After t he stimulation with immobilized anti-CD3 antibodies, both NK-type T cells p roduced much larger amounts of interferon-gamma (IFN-gamma) than CD8(+) T c ells. Both NK-type T cells also acquired a more potent cytotoxicity against NK-sensitive K562 cells than CD8(+) T cells while only CD56(+) T cells sho wed a potent cytotoxicity against NK-resistant Raji cells. After the stimul ation with a combination of interleukin (IL)-2, IL-12 and IL-15, the IFN-ga mma amounts produced were NK cells greater than or equal to CD56(+) T cells greater than or equal to CD57(+) T cells > CD8(+) T cells. The cytotoxicit ies against K562 cells were NK cells > CD56(+) T cells greater than or equa l to CD57(+) T cells > CD8(+) T cells while cytotoxicities against Raji cel ls were CD56(+) T cells >CD57(+) T cells greater than or equal to CD8(+) T cells greater than or equal to NK cells. However, the CD3-stimulated prolif eration of both NK-type T cells was smaller than that of CD8(+) T cells par tly because NK-type T cells were susceptible to apoptosis. In addition to N K cells, NK-type T cells but not CD8(+) T cells stimulated with cytokines, expressed cytoplasmic perforin and granzyme B. Furthermore, CD3-stimulated IFN-gamma production from peripheral blood mononuclear cells (PBMC) correla ted with the proportions of CD57(+) T cells in PBMC from donors. Our findin gs suggest that NK-type T cells play an important role in the T helper 1 re sponses and the immunological changes associated with ageing.