CD274 and COVID-19: The broad and sensitive proteomic analyses identified a subset of chemokines (CXCL5, CXCL10, CXCL11), immune modulators (Gal-9, PD-L1, MERTK), cytokines and their cognate receptors (IFN-gamma, IL-18, IL-18R1, LIF-R, MCP-2, MCP-3, TNF), and proteases (MMP-1), as being significantly elevated in COVID-19 patients compared to non-COVID-19 patients with similar symptoms.