CD4 and COVID-19: In addition, the CD4 + CD45RA+/CD4 + CD45RO+ and CD8 + CD45RA+/CD8 + CD45RO + ratios were reduced compared to healthy controls, but the CD4/CD8 ratio and absolute counts of Tregs in the peripheral blood of COVID-19 patients did not show statistically significant differences compared to those of the healthy controls (Figure 1(c)).