The R131 low-affinity allele of the Fc gamma RIIA receptor is associated with systemic lupus erythematosus but not with other autoimmune diseases in French Caucasians

Meta analysis on the association between FcgammaRIIa-R/H131 polymorphisms and systemic lupus erythematosus

In order to study the association between FcgammaRIIa gene polymorphisms and the risk of systemic lupus erythematosus (SLE) and lupus nephritis, relevant studies were identified from electronic databases. A meta-analysis of relevant studies was performed for heterogeneity test and pooled OR calculation. When all groups were pooled, a significant association of FcgammaRIIa-R131 allele and increased SLE risk was found. But this association was not observed in lupus nephritis. In the subgroup analysis, a clear effect of R allele in SLE was shown in European and Asian subgroups. Similarly, RR homozygous genotype was found to be a risk factor of SLE and lupus nephritis. The association between RR genotype and SLE was shown in European and Asian descents. However, the association between RR genotype and lupus nephritis was not found in any ethnic subgroups. Taken together, our study suggests that the FcgammaRIIa-R/H131 polymorphism might contribute to the susceptibility to SLE and lupus nephritis.

Fcgamma receptor IIA genotype and susceptibility to P. aeruginosa infection in patients with cystic fibrosis

It has been suggested that genes other than CFTR could modulate the severity of lung disease in cystic fibrosis (CF). Neutrophil Fcgamma receptor II (FcgammaRII) is involved in host defense against microorganisms and in inflammatory response. We evaluated the association between genetic variability of this gene and both airway infection with Pseudomonas aeruginosa and severity of lung disease in patients with CF. We studied 167 Italian unrelated patients with CF and 50 control subjects. The distribution of FcgammaRIIA genotypes in CF patients was compared with that in control subjects and the different genotypes were related with the presence or absence of P. aeruginosa infection and markers of disease severity in CF patients. The distribution of FcgammaRIIA genotypes was not significantly different between CF patients and controls. We observed that in CF patients with the same CFTR genotype (DeltaF508/DeltaF508), those carrying the R allele of FcgammaRIIA had an increased risk of acquiring chronic P. aeruginosa infection (P=0.042, R.R.: 4.38; 95% CI: 1.17/22.4). Moreover, the frequency of R/R genotype in patients with chronic P. aeruginosa infection seems to be higher than that of control subjects and patients without chronic infection. The observation that CF patients carrying the R allele of FcgammaRIIA are at higher risk of acquiring chronic P. aeruginosa infection suggests that the FcgammaRII loci genetic variation is contributing to this infection susceptibility.

Fc RIIa polymorphism: a susceptibility factor for immune complex-mediated lupus nephritis in Brazilian patients

BACKGROUND

Fc gamma RIIa is a low affinity receptor that has two co-dominantly expressed alleles, R131 and H131, which differ in their ability to bind immunoglobulin G (IgG) subclasses. Cells expressing H131 bind more efficiently complexed IgG2 and IgG3 than those expressing the R131 variant. The Fc gamma RIIa polymorphism has been shown to be associated with lupus nephritis. Here we evaluated the relevance of Fc gamma RIIa gene polymorphism in the development of lupus immune complex (IC)-mediated nephritis by comparing the genotype and allelic distribution of this receptor in lupus nephritis to ethnically matched healthy controls in Brazilians.

METHODS

119 systemic lupus erythematosus (SLE) patients and 48 healthy volunteers were recruited. Fc gamma RIIa genotyping was performed by PCR with allele-specific primers to distinguish between the two allelic forms (H131 and R131).

RESULTS

Comparison of Fc gamma RIIa genotypes distribution in SLE patients with nephritis and in controls showed a significant increase in Fc gamma RIIa-R131 homozygosity (P < or = 0.02). The genotype distribution in lupus nephritis (45% with Fc gamma RIIa-R/R131, 30% with H/R131 and 25% with H/H131) was distinct from that observed in controls (21% with Fc gamma RIIa-R/R131, 52% with H/R131 and 27% with H/H131). In contrast, there was no difference in the distribution of Fc gamma RIIa genotypes in lupus without nephritis and controls (P = 0.3). Reinforcing the relevance of Fc gamma RIIa polymorphism in IC-mediated nephritis, patients with renal failure had an over-representation of the R131 allele (70%) when compared with normal controls (47%) (P = 0.06).

CONCLUSIONS

The skewed distribution of Fc gamma RIIa genotypes with the predominance of homozygous R/R131 genotype observed in lupus nephritis emphasizes its importance as a heritable risk factor for IC-mediated renal injury in Brazilian lupus patients.

Role of the Fcgamma receptor IIA polymorphism in the antiphospholipid syndrome: an international meta-analysis

OBJECTIVE

To assess the impact of the FcgammaRIIA-R/H131 polymorphism on the risk for antiphospholipid syndrome (APS), both primary and secondary to systemic lupus erythematosus (SLE).

METHODS

This international meta-analysis combined data from 9 research teams. FcgammaRIIA-R/H131 genotypes were determined in 481 APS cases (206 with primary APS), 1,420 SLE controls, and 1,655 disease-free controls. Data were combined using fixed-effects and random-effects models.

RESULTS

Compared with disease-free controls, the RR genotype was enriched in the entire group of APS cases (odds ratio [OR] 1.65, 95% confidence interval [95% CI] 1.28-2.14); this was driven mostly by patients with secondary APS (OR 1.95, 95% CI 1.45-2.63). The excess of RR homozygotes but not heterozygotes among APS patients suggested a recessive mode of inheritance, rather than the additive model seen for SLE susceptibility, where RR conferred greatest risk, and RH intermediate risk, for SLE. This probably reflected the additional influence of another opposing genetic effect of HH homozygosity on APS predisposition (OR 0.72 for RH versus HH, 95% CI 0.55-0.96). Among SLE patients, those with APS were more frequently HH homozygotes than heterozygotes (OR 0.56 for RH versus HH, 95% CI 0.39-0.81). HH homozygosity also tended to predominate in primary APS compared with secondary APS (OR 0.50 for RR versus HH, 95% CI 0.25-0.99 by fixed-effects model). There was no significant between-study heterogeneity for any of these effects.

CONCLUSION

The FcgammaRIIA-R/H131 polymorphism is an important determinant of predisposition to APS, with different influences on SLE and APS susceptibility per se.

The genetic basis for systemic lupus erythematosus

Genetic factors play a major role in the development of lupus. More than 5% of cases are familial, and the concordance rate between identical twins is 40%. Genetic studies in mice suggest a complex mechanism of transmission involving interactions among several susceptibility genes and, probably, protective genes. Genetic studies in humans have identified nearly 50 chromosomal areas possibly involved in lupus transmission. Significant linkage has been found for at least six regions, two on chromosome 1, one near the HLA region on chromosome 6, and three on chromosomes 2, 4, and 16, respectively. Many candidate genes have been identified based on their location or possible pathogenic effects. Specific characteristics of the HLA region, as well as complement factor deficiencies, may promote nuclear antigen presentation, thereby triggering autoantibody production. The genetic polymorphism of cytokines and, perhaps, of the T-cell receptor (TCR) may contribute to deregulate lymphocyte activity. The polymorphism of the Fc receptors of immunoglobulins may affect immune complex clearance, thereby promoting tissue damage. Further genetic studies are needed to enrich the fund of knowledge on lupus and to identify new targets for treatment.

Role of the Fcgamma receptor IIa polymorphism in susceptibility to systemic lupus erythematosus and lupus nephritis: a meta-analysis

OBJECTIVE

To assess the impact of the Fcgamma receptor type IIa (FcgammaRIIa)-R/H131 polymorphism on the risk for systemic lupus erythematosus (SLE) and development of lupus nephritis.

METHODS

A meta-analysis was performed based on the Medline and Embase databases (last retrieval August 2001), assessment of bibliographies of pertinent articles, and additional data gathered after contact with primary investigators.

RESULTS

A total of 25 comparisons from 17 studies involving R/H131 genotyping of 1,405 patients with lupus nephritis, 1,709 SLE patients without nephritis, and 2,580 non-SLE controls were included. No association between RR genotype and risk of lupus nephritis relative to both other genotypes (odds ratio [OR] 1.05, 95% confidence interval [95% CI] 0.88-1.27) was demonstrated in the total meta-analysis or in any racial subgroup. The RR genotype was more frequent in SLE patients as a whole (OR 1.30, 95% CI 1.10-1.52) and in SLE patients without nephritis (OR 1.27, 95% CI 1.04-1.55) compared with disease-free controls. A potential dose-response relation between the R131 allele and the risk of SLE was also identified, with an OR of 1.23 for RR versus RH (95% CI 1.03-1.46). The OR was 1.55 for RR versus HH (95% CI 1.21-1.98). There was no significant heterogeneity between racial subgroups. The population-attributable fractions of SLE cases due to the FcgammaRIIa-R131 allele were 13%, 40%, and 24% in subjects of European, African, and Asian descent, respectively.

CONCLUSION

The FcgammaRIIa-R/H131 polymorphism represents a significant risk factor for SLE but has no clear effect on susceptibility for lupus nephritis.