CCL2 and COVID-19: The pathology of severe COVID-19 is characterized by elevated levels of proinflammatory cytokines, mainly tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-1β, granulocyte-macrophage colony-stimulating factor (GM-CSF), and chemokine (C-C-motif) ligand 2 (CCL2), many of which are produced and released by MCs [4,5,6].