Tregs are critical for control of self-reactive T cells that escape thymic selection and end up in the periphery. Treg subsets suppress effector T cell populations through the secretion of immunosuppressive molecules and inhibitory cytokines as well as cell contact–dependent mechanisms. In this issue of the
Christoph T. Berger, Christoph Hess
Schematic of the mechanism by which CD8+ Tregs suppress CD4+ T cells and implications for autoimmune disease.