CCL2 and COVID-19: The features of COVID-19–mediated CRS are distinct from those of bacterial CRS: 1) COVID-19 patients have a relatively lower elevation in the serum levels of inflammatory cytokines, including IL-6, IL-10, and MCP-1 and 2) these patients have a similar elevation of PAI-1 serum levels, which can be decreased by the inhibition of IL-6 signaling.