Moreover, the previous results suggest that loss of PD-1−/− receptor immune checkpoint signaling in the context of repetitive ISO-mediated injury results in the expansion of cytotoxic CD8+ lymphocytes in the heart, consistent with the development of “smoldering” CD8+ lymphocytic myocarditis that has been reported recently in cancer patients who are being treated with ICIs.12 This evidence concerns the gene CD8A and cancer.