Studies on the association of Fcγ receptor IIA, IIB, IIIA and IIIB polymorphisms with rheumatoid arthritis in the Japanese: evidence for a genetic interaction between HLA-DRB1 and FCGR3A

We recently detected a new single nucleotide polymorphism of FcγRIIB gene, which alters an amino acid within the transmembrane domain from Ile to Thr (I232T), and its association with SLE in the Japanese. This study was performed to examine whether FCGR2B-I232T was associated with susceptibility to rheumatoid arthritis in the Japanese. At the same time, FCGR2A, 3A and 3B polymorphisms were also examined. Genotyping of FCGR2B-I232T, FCGR2A-H131R, FCGR3A-F176V and FCGR3B-NA1/2 polymorphisms were performed using genomic DNA. Association with RA was analyzed in 382 Japanese patients with RA and 303 healthy individuals using a case–control approach. In addition, the same groups of patients and controls were genotyped for HLA-DRB1 to examine possible interaction with FCGR genes. Significantly different distribution of genotype, allele carrier and allele frequencies was not observed between patients with RA and healthy individuals in any of the four polymorphisms. When the subjects were stratified according to the carriage of HLA-DRB1 shared epitope (SE), significant increase of FCGR3A-176F/F genotype was observed in SE positive patients compared with SE positive healthy individuals (P=0.009, Pcorr=0.07). In conclusion, FCGR3A-176F/F genotype was considered to confer risk through genetic interaction with HLA-DRB1 SE.