CCR1 and COVID-19: Compared with CCR1− CD16+monocytes, there were 351 significantly highly expressed genes in CCR1+ CD16+monocytes, such as inflammatory and cytokine genes of IL1B, IL27, CXCL10, CXCL8, CD14, and OSM (FDR < 0.05, Fig. 4B and Additional file 2: Table S12), which have been documented to be associated with the inflammatory response and chemotaxis of immune cells among COVID-19 patients [10, 15, 66, 67].