CXCR4 and COVID-19: For example, we observed a decrease in the CXCR2+CXCR4–CD62L+ mature-homeostatic neutrophils and an increase in CD16+CD10+CXCR2+CXCR4+CD62L+ aged neutrophils in patients with COVID-19, indicating a potential link between these subpopulations and disease severity.