We could show that the difference between development of colitis (CD4-CreERt2/TR2f/f, dLck-Cre/TR2f/f) and a lethal systemic autoimmune syndrome (our thymic deletion model, CD4-Cre/TR2f/f, Lck-Cre/TR1f/f) lies in whether TGF-β signalling is disrupted later than or at the DP thymic stage, respectively. Here, CD4 is linked to colitis.