IFNG and COVID-19: Notably, CHIP (+) upregulated genes were uniquely associated with type II interferon (IFN) responses, which was not shown in CHIP (-) upregulated genes (Mann‒Whitney’s U test, P = 1.08e-3, IFN-γ) (Fig. 1e), potentially suggesting that a strong IFN-γ response in classical monocytes is a representative immunological signature in CHIP (+) severe COVID-19.