Analysis of the susceptibility of CD57 T cells to CD3-mediated apoptosis

After stimulation with anti-CD3 antibody in vitro, CD57(+) T cells showed a greater susceptibility to apoptosis than CD57(-)alphabetaT cell receptor (TCR)(+) T cells (regular alphabeta T cells). The apoptotic fraction of CD57(+) T cells showed an increased production of active caspase-3. An increase in both Fas expression and Fas-ligand (FasL) production was also observed in CD57(+) T cells, whereas the expression of survivin was suppressed in CD57(+) T cells compared to that of regular alphabeta T cells. CD57(+) T cells display a biased expansion of a few Vbeta T cell fractions in individuals, but such Vbeta T cells were not specifically susceptible to CD3-mediated apoptosis. The TCR expression level of CD57(+) T cells was much lower than that of regular T cells and anti-TCR antibody stimulation induced a smaller apoptotic proportion of CD57(+) T cells than did anti-CD3 antibody. Although the CD3epsilon expression levels were similar in both T cell subsets, the CD3zeta level of CD57(+) T cells was significantly higher than that of regular T cells. These results suggest that several apoptotic and anti-apoptotic molecules are involved in the CD3-induced apoptosis of CD57(+) T cells and raise the possibility that the imbalance in expression of the CD3epsilon and CD3zeta chains may also contribute to the susceptibility of CD57(+) T cells to undergo apoptosis.