S100A9 and COVID-19: Interestingly, many pro-inflammatory genes including S100A8 and S100A9, chemotaxis genes such as CXCR2 and FPR1, and NETosis-associated genes such as TIMP1 were highly expressed in neutrophils of ANPEP-high patients with COVID-19 compared with ANPEP-low patients with COVID-19 (Figure 4C).