It examines the differences in the levels of 21 cytokines, including IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ, IL-17A, IL-1β, IL-5, IL-12p70, IFN-α, IL-8, sCD25, sCD40L, sCD130, sTREM-1, TGF-β, G-CSF, GM-CSF, TGF-A, VEGF, and 5 chemokines, including IP-10, MIG, SDF-1, MCP-1, RANTES, in the serum of non-severe and severe COVID-19 patients. The gene discussed is CD40LG; the disease is COVID-19.