FcγRIIa polymorphism in Japanese patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an immune complex-mediated disease and organ damage is caused by the deposition of immune complex. Receptors which recognize the Fc portion of immunoglobulin G (FcgR) play a key role in the phagocytosis of immune complexes. As the gene encoding for FcgR of class IIa (FcγRIIa) has two allelic forms, H131 and R131, which differ in their affinity to IgG2, this polymorphism might have implications in handling immune complex. We studied the distribution of the FcγRIIa polymorphism in 90 Japanese patients with SLE. We also examined the association between FcγRIIa polymorphism and the disease activity of SLE and the histopathological findings of lupus nephritis. FcγRIIa polymorphism was determined by PCR and dot blot analysis. The allelic frequency of H131 in patients with SLE was significantly lower (H131/R131 ‘ 0.44/0.56) than that of normal controls (H131/R131 ‘ 0.62/0.38; P < 0.05). No significant association was observed between FcγRIIa polymorphism and the clinical parameters for the activity of SLE. There was no association between FcγRIIa polymorphism and the histological findings in lupus nephritis. The difference in the distribution of FcγRIIa alleles between patients with SLE and normal subjects indicates that this polymorphism is a candidate of susceptibility gene for SLE in Japanese.