For example, female-biased monocyte-nC, B cell lgG+, and CD4-T EM cells were observed in mild COVID-19 or healthy donors; yet, male-biased monocytes (including 14 enriched immune pathways [Toll-like receptor (TLR) signaling pathways, RIG-I-like receptor signaling pathway, cytokines and growth factors, and the IL-17 signaling pathway], FDR < 0.05) and NK cells were remarkably observed in severe COVID-19 patients only. This evidence concerns the gene CD4 and COVID-19.