CD4 and COVID-19: Cellular groups that were decreased in COVID-19 patients included several types of less activated Tregs (cTfr, naïve, and CM-like) in correlation with groups of DCs (pDC and cDC), CXCR4lo naïve CD4, naïve CD8, CD56hiCD16lo NK cells, and monocyte subgroups (intermediate, nonclassical, and HLA-DRhi cMono).