Interestingly, the elevated IgG gene expression was mainly due to IgG1 (IGHG1; Fig. 2f) and IgG3 (IGHG3; Supplementary Fig. S3d), but not IgG2 (IGHG2; Fig. 2g), which is in line with the presumed IgG1- and IgG3-switched phenotype of T-bet+ B cells both in MS and during viral infections.23 Here, IGHG2 is linked to viral infectious disease.