MALT1 and Autoimmunity: Together, these results clearly demonstrate that MALT1 proteolytic activity in T cells regulates CTLA-4 surface expression in Tregs and CD44+CD4+ T cells, indicating that MALT1 proteolytic activity influences Treg functionality in a T cell-intrinsic manner, since even a moderate decrease in CTLA-4 expression can lead to autoimmunity in humans (61).