Analysis of the susceptibility of CD57 + T cells to CD3‐mediated apoptosis

Summary After stimulation with anti‐CD3 antibody in vitro , CD57 + T cells showed a greater susceptibility to apoptosis than CD57 – αβT cell receptor (TCR) + T cells (regular αβ 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 αβ T cells. CD57 + T cells display a biased expansion of a few Vβ T cell fractions in individuals, but such Vβ 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 CD3ɛ expression levels were similar in both T cell subsets, the CD3ζ 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 CD3ɛ and CD3ζ chains may also contribute to the susceptibility of CD57 + T cells to undergo apoptosis.