SIgM indeed partially compensates for defective or absent IgA in mouse models of IgA deficiency and in human cohorts of selective IgA deficiency (Fadlallah et al, 2018, 2019; Catanzaro et al, 2019; Michaud et al, 2020; Sterlin et al, 2020). This evidence concerns the gene CD79A and selective IgA deficiency disease.