CD4 and systemic lupus erythematosus: Given the fact that a complete lack of functional CD4+FoxP3+ cells leads to severe autoimmune disease with a variety of lupus-like symptoms, these Treg in miR155-/- mice are likely still functional, since peripheral tolerance is still maintained in mir155-deficient controls (CO-/-) which did not show any signs of inflammation or autoimmune disease [9].