CCL2 and COVID-19: Several studies showed that the severity of COVID-19 symptoms positively correlated with blood levels of proinflammatory cytokines and chemokines (e.g., IL-1b, TNF-α, monocyte chemoattractant protein 1 [MCP-1], MCP-3, cytosolic carboxypeptidase 2 [CCL2], CCL3, IL-2, sIL-2RA, IL-6, IL-7, IL-17, IL-18, granulocyte colony-stimulating factor [G-CSF], interferon gamma-induced protein 10 [IP10], macrophage colony-stimulating factor [M-CSF], and microprotein 1a [MIP-1a]) and anti-inflammatory cytokines (e.g., IL-10) [33,34,35,36,37,38].