(2020) published significant increase in NKG2A expression on CD3+CD8+ and NK cells in COVID-19 patients compared to healthy controls and significant decline in its expression during recovery, what suggests that functional exhaustion of cytotoxic cells might attenuate the effectiveness of antiviral immunity and participate in disease pathogenesis (Zheng M. et al., 2020). This evidence concerns the gene KLRC1 and COVID-19.