Additionally, a single-cell transcriptomic evaluation of viral antigen-reactive CD4+ T cells of patients with SARS-CoV-2 infection found that the percentages of SARS-CoV-2-reactive Tregs, T follicular helper cells (Tfh), and cytotoxic T helper cells responsive to the viral infection were enhanced in hospitalized COVID-19 patients [60]. This evidence concerns the gene CD4 and COVID-19.