ISG15 and COVID-19: The direct comparison of the immune response in MIS-C and COVID-19 pediatric patients has revealed distinct patterns: while children with typical COVID-19 syndrome displayed a significant increase of IFN-α plasma levels and increased expression of type I IFNs inducible genes ISG15 and IFIT1 in granulocytes and PBMC, patients with MIS-C exhibited low-level expression of ISG15 and IFIT1 mRNAs, as observed in healthy controls.