After testing an independent cohort of 2,009 cases of ulcerative colitis and 1,580 controls, we identified 13 loci that were significantly associated with ulcerative colitis (P < 5 x 10(-8)), including the immunoglobulin receptor gene FCGR2A, 5p15, 2p16 and ORMDL3 (orosomucoid1-like 3).
In recent years, there has been renewed interest in the role of IgG in intestinal immunity, driven in part by a genetic association of an affinity-lowering variant of an IgG receptor, FcγRIIA, with protection from ulcerative colitis (UC), a subclass of inflammatory bowel disease (IBD).
Our suggestive finding that the association between dietary heme iron intake and risk of UC may be modified by a coding variant in FcγRIIA gene warrants additional investigation.
The TC haplotype constructed by the major allele of FCGR2A (rs1801274 and rs511278) was more prevalent in UC patients compared with controls (65.2% vs. 60.2%, p = 0.017).
Specifically, a variant of the activating receptor, FcγRIIA, with low affinity for IgG, confers protection against the development of ulcerative colitis, a subset of IBD, leading to a re-evaluation of the role of IgG and FcγRs in gastrointestinal tract immunity, an organ system traditionally associated with IgA.
After testing an independent cohort of 2,009 cases of ulcerative colitis and 1,580 controls, we identified 13 loci that were significantly associated with ulcerative colitis (P < 5 x 10(-8)), including the immunoglobulin receptor gene FCGR2A, 5p15, 2p16 and ORMDL3 (orosomucoid1-like 3).
We confirmed the associations of 10 known UC risk loci in Koreans: rs76418789 in IL23R (combined P = 1.25 × 10), rs4728142 in IRF5 (combined P = 3.17 × 10), rs1830610 near JAK2 (combined P = 2.28 × 10), rs1555791 near TNFRSF14 (combined P = 1.62 × 10), rs880790 between IL10-IL19 (combined P = 3.73 × 10), rs10185424 between IL1R2-IL1R1 (combined P = 1.54 × 10), rs6478108 in TNFSF15 (combined P = 9.28 × 10), rs861857 between UBE2L3-YDJC (combined P = 3.05 × 10), rs1801274 in FCGR2A (discovery P = 1.54 × 10), and rs17085007 between GPR12-USP12 (discovery P = 3.64 × 10).
Genome-wide association studies (GWASs) in UC implicate a FCGR2A variant that alters the binding affinity of the antibody receptor it encodes, FcγRIIA, for immunoglobulin G (IgG).