Fc gamma receptor IIIb polymorphism and systemic lupus erythematosus: association with disease susceptibility and identification of a novel FCGR3B*01 variant.

OBJECTIVE

The objective of this study was to evaluate the association between Fc gamma receptor IIIb polymorphism and susceptibility to systemic lupus erythematosus and clinical traits of the disease.

METHODS

Genomic DNA was obtained from 303 consecutive systemic lupus erythematosus patients and 300 healthy blood donors from the southeastern region of Brazil. The polymorphic region of the FCGR3B gene was sequenced and the alleles FCGR3B01, FCGR3B02 and FCGR3B*03 were analyzed.

RESULTS

The FCGR3B01 allele was more frequent in systemic lupus erythematosus patients (43.1%) while the FCGR3B02 allele prevailed among controls (63.7%) (P = 0.001). The FCGR3B03 allele was found equally in both groups. The FCGR3B01/01 (20.7%) and FCGR3B01/02 (41.1%) genotypes were more frequent among systemic lupus erythematosus patients (P = 0.028 and P = 0.012, respectively) while the FCGR3B02/02 genotype was more frequent in controls (45.5%) (P < 0.001). One variant of the FCGR3B01 allele previously described in Germany was found in only one control. A new variant of the FCGR3B01 allele with two substitutions (A227G/G277A) was found in one control. Three variants of the FCGR3B02 allele previously described in African-Americans, Brazilians, Chinese and Japanese were found in ten 10 patients and two controls. In addition, several single nucleotide polymorphisms at non-polymorphic positions were identified in both patients and controls.

CONCLUSION

Susceptibility to systemic lupus erythematosus was associated with the FCGR3B01 allele, as well as with the FCGR3B01/01 and FCGR3B01/*02 genotypes. No association was found between FCGR3B genotypes and clinical manifestations, disease severity or the presence of autoantibodies.