Abstract
Dysfunction in various parts of immune defence, such as immune response, immune complex clearance, and inflammation, has an impact on pathogenesis in systemic lupus erythematosus (SLE). We hypothesised that combinations of common variants of genes involved in these immune functions are associated with susceptibility to SLE. The following variants were analysed: HLA DR3, HLA DQ2, C4AQ0, Fcgamma receptor IIa (FcgammaRIIa) genotype R/R, Fcgamma receptor IIIa (FcRgammaIIIa) genotype F/F, mannan-binding lectin (MBL) genotype conferring a low serum concentration of MBL (MBL-low), and interleukin-1 receptor antagonist (IL-1Ra) genotype 2/2. Polymorphisms were analysed in 143 Caucasian patients with SLE and 200 healthy controls. HLA DR3 in SLE patients was in 90% part of the haplotype HLA DR3-DQ2-C4AQ0, which was strongly associated with SLE (odds ratio [OR] 2.8, 95% CI 1.7-4.5). Analysis of combinations of gene variants revealed that the strong association with SLE for HLA DR3-DQ2-C4AQ0 remained after combination with FcgammaRIIa R/R, FcgammaRIIIa F/F, and MBL-low (OR>2). Furthermore, the combination of the FcgammaRIIa R/R and IL-1Ra 2/2 genotypes yielded a strong correlation with SLE (OR 11.8, 95% CI 1.5-95.4). This study demonstrates that certain combinations of gene variants may increase susceptibility to SLE, suggesting this approach for future studies. It also confirms earlier findings regarding the HLA DR3-DQ2-C4AQ0 haplotype.