CD4 and COVID-19: As demonstrated in Figure 6, the proportion of CD4+ T cells was negatively correlated with the proportion of CD8+ T cells in male COVID-19 patients (Figure 6E; r = −0.7688, P=0.0093), as well as in males and females in the VP (Figure 6C,D) and HC groups (Figure 6A,B), whereas no significant correlation was observed in female COVID-19 patients (Figure 6F; r = −0.1042, P=0.7349).