Indeed, the total number of NK cells declines during the COVID-19 and the number of NK cells is simultaneously increased with the reduced expression of NKG2A after recovery (Yaqinuddin and Kashir, 2020; Qin et al., 2020), while this is associated with significantly decreased expression of the activation markers including CD107a, IFN-γ, IL-2, and TNF-α in T and NK cells of patients with severe COVID-19 (Antonioli et al., 2020; Zheng et al., 2020). This evidence concerns the gene IL2 and COVID-19.