CD4 and rheumatic myocarditis: Subsequently, Morris et al. (1993) reported that the frequency of CD4+ T cells was significantly higher in the peripheral blood of both ARF and RHD patients compared to healthy donors [21], while Oner et al. (2016) described a lower frequency of CD8+ T cells in patients with acute rheumatic carditis and regurgitation compared to those with regurgitation regression [22].