CCL2 and COVID-19: MCP-1 upregulation was observed in most COVID-19 patients, whether cases were severe (296.7 pg/mL ± 128 pg/mL) or mild (215.9 pg/mL ± 67.4 pg/mL), versus healthy controls (36.2 pg/mL ± 6.7 pg/mL; Fig. 1a; P < 0.01).