Interestingly, no difference in the number of Foxp3+ Tregs could be found between vehicle-treated and mepazine-treated mice, demonstrating that a balanced inhibition of TCR signaling by specific inhibition of MALT1 proteolytic activity, leaving its scaffolding function intact, does not affect the development of Tregs and holds promise for the treatment of autoimmune disease. Here, MALT1 is linked to autoimmune disease.