IMMUNOBIOLOGY

The effector T-cell lineage shows great plasticity. Th17 cells are acknowledged to be instrumental in the response against microbial infection, but are also associated with autoimmune inflammatory processes. Here, we re-port that human regulatory T cells (CD4posCD25highFoxp3posCD127negCD27pos) can differentiate into IL-17–producing cells, when stimulated by allogeneic antigen-presenting cells, especially monocytes, in the presence of rhIL-2/rhIL-15. These regula-tory T cell (Treg)–derived IL-17–producing cells showed high expression of the Th17-related transcription factor RORt and were positively identified by CCR6 expression. This differentiation process was enhance