Excessive activation of the complement cascade, e.g. by antibodies against SARS-CoV-2 (30) or the activation of the lectin pathway (12), may lead to an over-production of C5a, resulting in cytokine storm, severe lung inflammation, infiltration of immune cells, endothelial dysfunction and thromboinflammation (40, 41). The gene discussed is C5AR1; the disease is endothelial dysfunction.