Cutting edge:: In contrast to effector T cells, CD4+CD25+ FoxP3+ regulatory T cells are highly susceptible to CD95 ligand- but not to TCR-mediated cell death

CD4(+) CD25(+) FoxP3(+) regulatory T cells (T-reg) suppress T cell function and protect rodents from autoimmune disease. Regulation of T-reg during an immune response is of major importance. Enhanced survival of T-reg is beneficial inautoimmunedisease, where as increased depletion by apoptosis is advantageous in cancer. We show here that freshly isolated FACS-sorted T-reg are highly sensitive toward CD95-mediated apoptosis, whereas other T cell populations are resistant to CD95-induced apoptosis shortly after isolation. In contrast, TCR restimulation of T-reg in vitro reg revealed a reduced sensitivity toward activation-induced cell death compared with CD4(+) CD25(-)T cells. Thus, the apoptosis phenotype of T is unique in comparison to reg other T cells, and this might be further explored for novel therapeutic modulations of Treg.