Pro-inflammatory cytokines (e.g. IL-6, IL-8, G-CSF), the complement factor C5a, antigen-antibody complexes and platelet derived factors (e.g. platelet factor 4 (PF4) and RANTES), whose circulating levels are all increased in patients with severe COVID-19 (5, 65, 91, 167, 174, 175), have been proposed as potential mediators of NET formation (65, 91, 167, 173). The gene discussed is PF4; the disease is COVID-19.