However, in COVID-19 patients, the total number of CD4+ and CD8+ T cells was significantly reduced, and their phenotype exhibited exhaustion markers, which usually lead to the functional impairment of T cells (Diao et al., 2020; Zheng H. Y. et al., 2020; Zheng M. et al., 2020). The gene discussed is CD8A; the disease is COVID-19.