CCL2 and COVID-19: The levels of pro-inflammatory cytokines, such as IL-2, IL-7, G-CSF, IP-10, MCP-1, MIP-1A and TNF-α in plasma were higher especially in severe COVID-19 patients, and T cells, macrophages and natural killer cells rapidly proliferate and are highly activated, accompanied by overproduction of immune or non-immune defense cells and the release of more than 150 inflammatory cytokines and chemical mediators13–16.