To delineate the immune repertoire of anti‐CTLA‐4 m2a antibody‐associated myocarditis in the peak inflammatory phases, we performed flow cytometry experiments to collect live cardiac CD45+ leukocytes on day 21 post‐initial immunization and subjected the cells to single‐cell RNA sequencing (scRNA‐seq) (Figure S1d,e, Supporting Information). Here, CTLA4 is linked to myocarditis.