CD4 and COVID-19: Using a gating strategy depicted in Figure S1, we analyzed the frequencies of total CD19+, CD3+, CD8+, CD4+, conventional CD4+ T (Tconv) (CD4+Foxp3-), and Treg (CD4+Foxp3+) lymphocytes from PBMCs of the entire cohort of hospitalized patients recruited during the first and second COVID-19 waves in Córdoba (Argentina) with moderate (MD) and severe (SD) COVID-19 disease.