CTLA4 and multiple sclerosis: Furthermore, multiple sclerosis after CTLA‐4 blockade by ipilimumab has been reported in one case where the clonally expanded T cell receptor sequences shared between the CSF and melanoma suggest preformed T cell memory led to the CNS disease.16 Similar close clonal relationships of T cells are recognized between tumor and cardiac tissue in post‐checkpoint inhibitor myocarditis,12 supporting the notion that many irAEs are T cell‐mediated.