CSF3 and COVID-19: The activation of macrophages, epithelial cells, and, possibly, endothelial cells is responsible for the elevated serum levels of proinflammatory cytokines (interleukins (IL)-1β and IL-18, IL-6) chemokines (CCL2, CCL3, CXCL8, CXCL9, and CXCL10, CXCL11), and growth factors (G-CSF and HGF) that contribute to the pathogenic inflammation responsible for the severity of the symptoms of COVID-19 [11,12,13].