In contrast, the frequencies of CD3+CD8+ T cells (Figure 6D), PD-1+CD3+ T cells (Figure 6F), PD-1+CD4+ T cells (Figure 6G), and PD-1+CD8+ T cells (Figure 6H) were markedly elevated in SLE patients compared with NCs. Here, CD4 is linked to systemic lupus erythematosus.