A recent study has shown that CD4+ and CD8+ T cells isolated during the acute phase of coronavirus disease 2019 (COVID-19) patients produce tumor necrosis factor (TNF), interferon-γ, interleukin (IL)-2 and high levels of IL-17 after polyclonal activation, suggesting a detrimental role of IL-17 during the excessive inflammatory response observed in COVID-19 infection [51]. This evidence concerns the gene CD4 and COVID-19.