The higher median IgM, IgA, and IgG1 values in the sera of the MIS-C cohort to some of the COVID-19 Ags may relate to the higher type-2 cytokines (IL-4, IL-5, IL-6, and IL-13) and IL-21 enhanced Tfh activity known to promote B-cell activities, as mentioned earlier. This evidence concerns the gene IL21 and COVID-19.