BACH2 and inflammatory bowel disease: In order to assess the level of methylation in CpG islands of the five candidate genes (BACH2, MGAT3, IKZF1, LAMB1, and IL6ST), associated with both IBD and IgG glycosylation by GWAS, we developed several pyrosequencing assays for each of the genes (Fig. 1 and Additional file 2: Figure S1).