Fourth, it is intriguing that complement factors and regulators C4, Factor B, C1-inhibitor and C1s, which were found to be significantly elevated in acute MIS-C in our current study, were all reported to respond with increased gene expression to interferon gamma and LPS stimuli in mouse macrophage models16,17. The gene discussed is SERPING1; the disease is COVID-19–associated multisystem inflammatory syndrome in children.