Refusing to be suppressed

On page 737, Fahlén et al. show that colitis-inducing effector T cells that cannot respond to the suppressive cytokine TGF-β refuse to be controlled by regulatory T (T reg) cells.Naturally occurring T reg cells suppress the activity of effector CD4⁺ T cells and are essential for the prevention of autoimmune disease and chronic inflammation. TGF-β appears to be required for T reg cell activity, but determining which cells produce TGF-β and which cells respond to it has proven difficult.

Fahlén and colleagues now attempt to define the role of TGF-β in a mouse model of T cell–induced colitis. In this model, colitis can be reversed when CD4⁺CD25⁺ T reg cells are provided along with the disease-inducing effector cells. The authors showed that...