CCL2 and pneumonia: COVID-19 patients who succumb to pneumonia and hypoxia had one hallmark feature of the profound inflammatory state that marked elevation of serum inflammatory cytokines (IL-6, IFN-γ, IL-1β, TNF-α and TGF-β) and chemokines (CCL2, CCL5, CXCL8 and CXCL10) [29].