CD4 and COVID-19: Consistent with this, the clinical data of COVID-19-children showed that the levels of coagulation indicators such as APTT, PT and D-dimer, the status of immune cell activation such as the ratios of CD3+CD4+ and CD3+CD8+, and the levels of inflammatory factors such as IFN-γ and IL-1β, generally followed in the normal range (Table 1).