Of the eight functional domains analyzed, five (receptor binding site [RBS], esterase domain, conserved glycosylation sites, Cal09 glycosylation site, and the antigenic sites) were preferentially targeted by IgA of HW individuals, while only the fusion domain was preferentially targeted by IgA antibodies from individuals with obesity (Table 1; Fig. 5; Fig. S11C to E). Here, CD79A is linked to obesity due to melanocortin 4 receptor deficiency.