While total IgG1, IgG2, IgG3, and IgG4 subclass Abs were significantly higher in the sera of IBD patients compared to healthy donors (data not shown), the profile of the IgG humoral response in IBD patients also revealed increases in Mycobacteria-specific IgG1 and IgG2 Abs (Figure 1). This evidence concerns the gene IGHG3 and inflammatory bowel disease.