Human Fc gamma receptor IIA (FcγRIIA) genotyping and association with systemic lupus erythematosus (SLE) in Chinese and Malays in Malaysia

SLE is an autoimmune and polygenic disorder characterized by an accumulation and deposition of immune complexes. Several studies have indicated differential impact of FcγR polymorphism genotypes in different ethnic groups studied. The Fc receptor for IgG class IIA gene (FcγRIIA) occurs in two allelic forms. The allele FcγRIIA-H131 encodes a receptor with a histidine at the 131 amino acid position; the other allele FcγRIIA-R131 encodes an arginine. This polymorphism is believed to determine the affinity of the receptor for hIgG2 in immune complexes. FcγRIIA-H131 has a higher capacity for hIgG2 compared to FcγRIIA-R131 as measured by in vitro studies of insoluble immune complex clearance. We have investigated the polymorphism for FcγRIIA using a novel polymerase chain reaction-allele specific primer (PCR-ASP) method designed specifically to distinguish the two allelic forms. Our studies were based on 175 Chinese and 50 Malays SLE patients as well as 108 and 50 ethnically matched healthy controls for the respective groups. Analysis of the data (χ² test with Yates correction factors and odds ratios) revealed that there were no significant differences between SLE patients and controls. We have not found evidence of a protective effect conferred by FcγRIIA-H131 in the ethnic groups studied.