Methods: T-lymphocytes (including Th cells, regulatory T-lymphocytes, CD4+ initial T-lymphocytes, CD4+ memory T-lymphocytes, CD4+ T-lymphocytes functional subsets, Tc cells, CD8+ initial T-lymphocytes, CD8+ memory T-lymphocytes, and CD8+ T-lymphocyte functional subpopulations) were isolated, by flow cytometry, from peripheral blood specimens of 60 COVID-19 patients (experimental group) and 36 healthy controls (control group). The gene discussed is CD8A; the disease is COVID-19.