SARS-CoV-2-specific CD4+ T cells produce IL-2, IFN-γ, and tumor necrosis factor-α (TNF-α), increasing the activation of Th1 immune response and cell-mediated immunity (Figure 2) [2], whereas virus-specific memory CD8+ T cells are involved in host defense from SARS-CoV-2 infection by the secretion of IFN-γ, TNF-α, IL-2, and cytolytic molecules such as granzyme B [44]. The gene discussed is IFNG; the disease is COVID-19.