As shown in Table 4, except for IgG 1/IgG 4, LY #, and HGB, the severe COVID-19 group exhibited significantly elevated levels of IL-2, IL-6, IgG 2/IgG 1, IgG Sum/IgG 1, IgG 2/IgG Sum, CRP, PT, INR, DD, WBC, NE #, NLR, RDW, and PDW in comparison to the non-severe COVID-19 group (p<0.05). Here, IL2 is linked to COVID-19.