FACS analysis illustrated that, in comparison to healthy controls, especially ICU patients with COVID-19 disease showed markedly higher percentages of PD-1+CD8+ and CD4+ T cells, with a trend to show higher PD-1 levels on PD-1+CD8+ or CD4+ T cells (Figures 3A,B), indicating that SARS-CoV-2 can drive T cell exhaustion in COVID-19 patients, particularly in those requiring ICU care. This evidence concerns the gene CD4 and COVID-19.