CXCL10 and COVID-19: Levels of circulating factors including interleukin (IL)-6, IL-18, Interferon (IFN)-γ, IL-15, Tumor Necrosis Factor (TNF)-α, IL-1α, IL-1β, IFN-γ-inducible protein (IP-10), and IL-2 are significantly elevated in patients with moderate or severe COVID-19 and particularly in the fatal course of disease (3, 5).