Only genuine CD4+CD25+ Tregs may be friends or foes

In their recent paper, Stanzani et al sought to ascertain whether the relationship between donor CD4 CD25 regulatory T cells (Tregs) and graft-versus-host disease (GVHD) severity, found in murine transplantation, would hold up in humans. With this aim, they measured CD4 and CD8 T cells coexpressing CD25 within 60 donor grafts infused into matched siblings, reaching the unexpected conclusion that higher numbers of donor CD4 CD25 (as well as CD8 CD25 ) T cells correlated with an increased risk for GVHD. A similar association was stated for the CD4 CD25high subset, but data were not shown. Thus, it was clear that authors referred to Tregs