Enhanced Severe Acute Respiratory Syndrome Coronavirus 2 Antigen-Specific Systemic Immune Responses in Multisystem Inflammatory Syndrome in Children and Reversal After Recovery.

<bold>Background: </bold>Multisystem inflammatory syndrome in children (MIS-C) presents with inflammation and pathology of multiple organs in the pediatric population in the weeks following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.<bold>Methods: </bold>We characterized the SARS-CoV-2 antigen-specific cytokine and chemokine responses in children with MIS-C, coronavirus disease 2019 (COVID-19), and other infectious diseases.<bold>Results: </bold>MIS-C is characterized by elevated levels of type 1 (interferon-γ, interleukin [IL] 2), type 2 (IL-4, IL-13), type 17 (IL-17), and other proinflammatory cytokines (IL-1α, IL-6, IL-12p70, IL-18, and granulocyte-macrophage colony-stimulating factor) in comparison to COVID-19 and other infectious diseases following stimulation with SARS-CoV-2-specific antigens. Similarly, upon SARS-CoV-2 antigen stimulation, CCL2, CCL3, and CXCL10 chemokines were significantly elevated in children with MIS-C in comparison to the other 2 groups. Principal component analysis based on these cytokines and chemokines could clearly distinguish MIS-C from both COVID-19 and other infections. In addition, these responses were significantly diminished and normalized 6-9 months after recovery.<bold>Conclusions: </bold>Our data suggest that MIS-C is characterized by an enhanced production of cytokines and chemokines that may be associated with disease pathogenesis. [ABSTRACT FROM AUTHOR]