CD4 and COVID-19: The prevalence of lymphopenia differed among the patients with different disease severities, with 72.7% developed in severe cases and 10.0% in the moderate case.94 Patients with severe COVID-19 showed considerably decrease in the counts of circulating memory CD4+ T cells, CD8+ T cells and regulatory T cells (Tregs).94 Despite reduced CD8+ T-cell counts, their histocompatibility complex (MHC) II cell surface receptor (HLA-DR) expression was higher in patients with severe COVID-19 than moderate cases.