CCL4 and COVID-19: When plasma levels of cytokines and chemokines were analysed using a 30-plex kit, several of these (IFN-γ, TNF-α, IL-18, IL-7, IL-10, IL-15, CXCL8, CXCL10, CCL2, CCL3, and CCL4) were significantly increased in all COVID-19 patient groups as compared to HCs (Figure 4).