CD4 and COVID-19: In the evaluation of exhaustion markers, CD127+ and PD-1+ CD4+ T cell subpopulations were increased in patients who recovered from COVID-19 as compared with healthy controls, and they were at comparable levels to those observed in patients with COVID-19 (Figure 1, A–D), while 2B4+CD4+ T cell levels were similar to that of healthy controls but higher compared with patients with COVID-19 (Figure 1, E and F).