CD8A and myocardial infarction: Importantly, as previously suggested,17 depletion of CD8+ T cells protected mice from immune-mediated myocardial damage, and another recent study confirms pathogenic effects of CD8+ T cells after MI.18 Consistent with single cell sequencing data above (Figure 1H and 1I), a significant proportion of CD3+ cells in the heart expressed neither CD4+ nor CD8+ (Figure 5C).