Using functional cellular assays of endotoxin and NLRP3 responses, alongside high dimensional cytokine, mass cytometry, and scRNA-seq analysis, we studied the immune landscape of MIS-C from acute to convalescence stages, comparing it with severe paediatric COVID-19, other non-SARS-CoV-2 related paediatric infections, and healthy children. The gene discussed is NLRP3; the disease is COVID-19.