CCL2 and COVID-19: However, the positive correlations found in COVID-19 patients between IL-22R1+ classical monocytes and plasma MCP-1 concentrations and between IL-22R1+ pDC and the plasma IP-10 levels in patients with a severe disease suggest a deleterious effect of IL-22R1 expressing cells as both MCP-1 and IP-10 levels are associated with the severity of the disease and pathological lung inflammation (14, 45).