A long asymptomatic period is observed before the onset of the clinical autoimmune diseases in CTLA‐4 haploinsufficiency, we can hypothesise that CTLA‐4 deficiency can be compensated by other Treg mechanisms of suppression for years but eventually leads to autoimmune diseases because Treg cell mechanisms of suppression are not redundant. Here, CTLA4 is linked to autoimmune disease.