Role of the Fcγ receptor IIIA-V/F158 polymorphism in susceptibility to systemic lupus erythematosus and lupus nephritis: a meta-analysis

Comparison of real-time quantitative PCR and two digital PCR platforms to detect copy number variation in FCGR3B

The importance of structural genetic variants, such as copy number variations (CNVs), in modulating human disease is being increasingly recognized. Several clinical conditions require investigation of human neutrophil antigen (HNA-1), which is encoded by the Fc gamma receptor IIIb gene (FCGR3B), including suspicion of neutropenia, infections, and proactive testing of blood component donors to reduce the potential risk in transfusion. In this study, we compared real-time quantitative polymerase chain reaction (qPCR) with two digital PCR (dPCR) platforms, namely droplet digital PCR and an array-based platform, to determine copy numbers (CNs) in FCGR3B. We initially tested 400 anonymous blood donors with qPCR using a commercially available TaqMan probe assay (Applied Biosystems) on a Quant Studio 12 Flex. CNs was determined for all 400 tested individuals with CNs ranging from zero to four. Zero copies were detected in 0.2% (1/400), one copy was detected in 3.8% (15/400), two copies were detected in 87.8% (351/400), three copies were detected in 8.0% (32/400), and four copies were detected in 0.2% (1/400) of tested individuals. From this cohort, we selected 32 donors with CNs from zero to four for analyses with Digital Real-Time PCR (dPCR) using Lab on an array (LOAA) on an On-Point analyzer from Optolane Technologies Inc. and the Droplet Digital PCR (ddPCR) platform from Bio-Rad Laboratories. We compared the obtained CNs of FCGR3B on the three platforms and found full concordance between the CNs obtained. We therefore conclude that all three platforms can be used for quantification of CNs for FCGR3B, and although dPCR has some advantages over qPCR, it was not necessary for reliably estimating CNs of the FCGR3B gene.

Genetic variations in low-to-medium-affinity Fcγ receptors and autoimmune neutropenia in early childhood in a Danish cohort

Autoimmune neutropenia (AIN) in early childhood is caused by autoantibodies directed against antigens on the neutrophil membrane and is a frequent cause of neutropenia in children. Association of AIN with Fcγ receptor (FCGR) 3B variants is well described. In this study, we investigate genetic variations in the FCGR locus and copy number variation of FCGR3B. A total of 130 antibody-positive AIN patients, 64 with specific anti-HNA-1a antibodies and 66 with broad-reacting anti-FcγRIIIb antibodies, were genotyped with a multiplex ligation probe assay and compared with healthy controls. Positive findings were confirmed with real-time q-PCR. We determined copy numbers of the FCGR2 and FCGR3 genes and the following SNPs: FCGR2A Q62W (rs201218628), FCGR2A H166R (rs1801274), FCGR2B I232T (rs1050501), FCGR3A V176F (rs396991), haplotypes for FCGR2B/C promoters (rs3219018/rs780467580), FCGR2C STOP/ORF and HNA-1 genotypes in FCGR3B (rs447536, rs448740, rs52820103, rs428888 and rs2290834). Generally, associations were antibody specific, with all associations being representative of the anti-HNA-1a-positive group, while the only association found in the anti-FcγRIIIb group was with the HNA-1 genotype. An increased risk of AIN was observed for patients with one copy of FCGR3B; the HNA genotypes HNA-1a, HNA-1aa or HNA-1aac; the FCGR2A 166H and FCGR2B 232I variations; and no copies of FCGR2B 2B.4. A decreased risk was observed for HNA genotype HNA-1bb; FCGR2A 166R; FCGR2B 232T; and one copy of FCGR2B promoter 2B.4. We conclude that in our Danish cohort, there was a strong association between variation in the FCGR locus and AIN. The findings of different genetic associations between autoantibody groups could indicate the presence of two different disease entities and disease heterogeneity.

An update on genetic susceptibility in lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by multiple system involvement and positive serum autoantibodies. Lupus nephritis (LN) is the most common and serious complication of SLE, and it is the main cause of death in patients with SLE. Abnormalities in the immune system lead to LN and involve a variety of cells (T cells, B cells, macrophages, NK cells, etc.), cytokines (interleukin, tumor necrosis factor α, etc.) and their related pathways. Previous studies have shown that the interactions of genetic, epigenetic and environmental factors contribute to the pathogenesis and development of LN. In recent years, one genome-wide association study (GWAS) and a number of gene association studies have explored the susceptibility genes of LN, including immunization-, inflammation-, adhesion- and other pathway-related genes. These genes participate in or suggest the pathogenesis and progression of LN. In this review, we summarize the genetic susceptibility of LN and discuss the possible mechanism underlying the susceptibility genes of LN.

An update on genetic susceptibility in lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by multiple system involvement and positive serum autoantibodies. Lupus nephritis (LN) is the most common and serious complication of SLE, and it is the main cause of death in patients with SLE. Abnormalities in the immune system lead to LN and involve a variety of cells (T cells, B cells, macrophages, NK cells, etc.), cytokines (interleukin, tumor necrosis factor α, etc.) and their related pathways. Previous studies have shown that the interactions of genetic, epigenetic and environmental factors contribute to the pathogenesis and development of LN. In recent years, one genome-wide association study (GWAS) and a number of gene association studies have explored the susceptibility genes of LN, including immunization-, inflammation-, adhesion- and other pathway-related genes. These genes participate in or suggest the pathogenesis and progression of LN. In this review, we summarize the genetic susceptibility of LN and discuss the possible mechanism underlying the susceptibility genes of LN.

Extensive Ethnic Variation and Linkage Disequilibrium at the FCGR2/3 Locus: Different Genetic Associations Revealed in Kawasaki Disease

The human Fc-gamma receptors (FcγRs) link adaptive and innate immunity by binding immunoglobulin G (IgG). All human low-affinity FcγRs are encoded by the FCGR2/3 locus containing functional single nucleotide polymorphisms (SNPs) and gene copy number variants. This locus is notoriously difficult to genotype and high-throughput methods commonly used focus on only a few SNPs. We performed multiplex ligation-dependent probe amplification for all relevant genetic variations at the FCGR2/3 locus in >4,000 individuals to define linkage disequilibrium (LD) and allele frequencies in different populations. Strong LD and extensive ethnic variation in allele frequencies was found across the locus. LD was strongest for the FCGR2C-ORF haplotype (rs759550223+rs76277413), which leads to expression of FcγRIIc. In Europeans, the FCGR2C-ORF haplotype showed strong LD with, among others, rs201218628 (FCGR2A-Q27W, r² = 0.63). LD between these two variants was weaker (r² = 0.17) in Africans, whereas the FCGR2C-ORF haplotype was nearly absent in Asians (minor allele frequency <0.005%). The FCGR2C-ORF haplotype and rs1801274 (FCGR2A-H131R) were in weak LD (r² = 0.08) in Europeans. We evaluated the importance of ethnic variation and LD in Kawasaki Disease (KD), an acute vasculitis in children with increased incidence in Asians. An association of rs1801274 with KD was previously shown in ethnically diverse genome-wide association studies. Now, we show in 1,028 European KD patients that the FCGR2C-ORF haplotype, although nearly absent in Asians, was more strongly associated with susceptibility to KD than rs1801274 in Europeans. Our data illustrate the importance of interpreting findings of association studies concerning the FCGR2/3 locus with knowledge of LD and ethnic variation.

Precision medicine in lupus nephritis: can biomarkers get us there?

Patients with systemic lupus erythematosus frequently develop lupus nephritis (LN), a condition that can lead to end-stage kidney disease. Multiple serum and urine biomarkers for LN have been proposed in recent years, yet none have become incorporated into clinical use. The majority of studies have been single center with significant variability in cohorts, assays, and sample storage, leading to inconclusive results. It has become clear that no single biomarker is likely to be sufficient to diagnose LN, identify flares, and define the response to therapy and prognosis. A more likely scenario is a panel of urine, serum, tissue, and genetic biomarkers. In this review, we summarize traditional and novel biomarkers and discuss how they may be utilized in order to bring precision medicine to clinical practice in LN.

FcγRIIa defunctioning polymorphism in paediatric patients with renal allograft

Introduction

Fc gamma receptor (FcγR) IIa is considered the most widely distributed of the three classes of Fc receptors, and it expresses an allelic polymorphism. This type of polymorphism may modify the immune response and may be an important factor for some diseases. The aim of the study reported herein was to evaluate the association between the FcγRIIa polymorphism and susceptibility to both end-stage renal disease (ESRD) and acute kidney graft rejection (AR) in children who have undergone renal transplantation.

Material and methods

The study evaluated 70 children who had undergone transplantation and 60 healthy subjects. AR was observed in 25 children.

Results

FcγRIIa genotypes and alleles were significantly different between transplantation patients and the control group. The assessment for FcγR of the groups in which AR was present showed that there was only a risk of having an acute rejection in homozygous genotype RR.

Conclusions

FcγRIIa RR genotype and allele frequency was increased in paediatric renal transplant recipients. The present findings showed that FcγRIIa genotype may be related to ESRD disease susceptibility, and FcγRIIa polymorphisms seemed to affect AR.

Novel biomarkers for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex and highly heterogeneous disease. By now, no novel drug has been approved by the US FDA in the past 50 years, except Belimumab, a monoclonal antibody to inhibit B-cell activating factor. The stagnating drug development of lupus may be due to our limited understanding of disease etiopathogenesis and the extreme heterogeneity of patient population. Thus, the individualized treatment for SLE becomes necessary. Recently, biomarkers have shown potential in individualized treatment. This review comprehensively summarizes novel potential biomarkers, discusses their current status in preclinical studies and clinical use, sensitivity to treatments and correlation with the disease activity, and provides an insight into the possibility of biomarkers in the utilization of individualized treatment for SLE.

Comprehensive Assessment of the Association between FCGRs polymorphisms and the risk of systemic lupus erythematosus: Evidence from a Meta-Analysis

We performed a meta analysis to assess the relationship of FCGRs polymorphisms with the risk of SLE. Thirty-five articles (including up to 5741 cases and 6530 controls) were recruited for meta-analysis. The strongest association was observed between FCGR2B rs1050501 and SLE under the recessive genotypic model of C allele in the overall population (CC vs CT/TT, OR = 1.754, 95%CI: 1.422–2.165, P = 1.61 × 10⁻⁷) and in Asian population (CC vs CT/TT, OR = 1.784, 95%CI; 1.408–2.261, P = 1.67 × 10⁻⁶). We also found that FCGR3A rs396991 were significant association with the susceptibility to SLE in overall population in recessive model of T allele (TT vs TG/GG, OR = 1.263, 95%CI: 1.123–1.421, P = 9.62 × 10⁻⁵). The results also showed that significant association between FCGR2A rs1801274 and SLE under the allelic model in the overall population (OR = 0.879 per A allele, 95%CI: 0.819–0.943, P = 3.31 × 10⁻⁴). The meta-analysis indicated that FCGR3B copy number polymorphism NA1·NA2 was modestly associated with SLE in overall population (OR = 0.851 per NA1, 95%CI: 0.772–0.938, P = 1.2 × 10⁻³). We concluded that FCGR2B rs1050501 C allele and FCGR3A rs396991 T allele might contribute to susceptibility and development of SLE, and were under recessive association model. While, FCGR2A rs1801274 A allele and FCGR3B NA1 were associated with SLE and reduced the risk of SLE.

Genetic Variants That Are Associated with Neuropsychiatric Systemic Lupus Erythematosus

OBJECTIVE

While genetic risks have been implicated in systemic lupus erythematosus (SLE), the involvement of various genotypes in neuropsychiatric SLE (NPSLE) remains uncertain. The present metaanalysis aimed to combine data from different studies and evaluate the association between each genotype and the risk of developing NPSLE.

METHODS

Studies were searched and retrieved from online databases (PubMed, EMBASE, BIOSIS, and ScienceDirect). Case-control studies were chosen if they reported genotype frequencies of the γ Fc region (FCγR) receptors II-A, III-A, and III-B; tumor necrosis factor-α (TNF-α); mannan-binding lectin (MBL); integrin alpha M (ITGAM); interleukin (IL) 1, IL-1β, and IL-6; IL-10 promoter; and vitamin D genes. The OR were used to assess the strength of this association between patients with NPSLE and SLE.

RESULTS

A total of 33 studies were considered in this metaanalysis. The results suggest that these genotypes demonstrated a significant association with NPSLE: the homozygous FCγR IIIa 158 FF genotype (OR 1.89, p = 0.03 for FF vs VV + FV), heterozygous FCγR IIIb NA1/2 genotype (OR 2.14, p = 0.03 for NA1/2 vs NA1/1; OR 1.81, p = 0.04 for NA1/2 vs NA1/1 + NA2/2), and homozygous ITGAM rs1143679 HH genotype (OR 3.39, p = 0.04 for HH vs RH; OR 3.11, p = 0.048 for HH vs RR + RH). Polymorphisms of the TNF-α, MBL2, IL-1, IL-1β, IL-6, IL-10 promoter, and vitamin D receptor genes did not show a statistically significant association with the risk of developing NPSLE (p > 0.05).

CONCLUSION

This metaanalysis indicates that polymorphisms in the pathways of immune complex clearance, such as the FcγRIIIa, FcγRIIIb, and ITGAM genotypes, are potential susceptibility genes for NPSLE.

Lupus Nephritis in Asia: Clinical Features and Management

BACKGROUND

Lupus nephritis (LN) is a common and severe organ involvement manifesting itself in systemic lupus erythematosus (SLE). There is a considerable difference in prevalence, severity, treatment response and outcomes between Asian LN patients and LN patients from other racial backgrounds.

SUMMARY

Asian SLE patients have a higher prevalence of LN than Caucasian SLE patients and often present with a more severe disease. Increasing data from genetic studies, accompanied by progress in high-throughput genotyping, have advanced our knowledge about genetic predispositions that might partly contribute to the clinical variations observed. Corticosteroids combined with either cyclophosphamide (CYC) or mycophenolic acid (MPA) is the current standard-of-care induction regimen for severe LN irrespective of race or ethnicity. However, the preference for MPA or CYC, and possibly the optimum dose for MPA, is influenced by the patient's origin. Also, there is an insufficient evidence base for reduced-dose intravenous CYC in Asian patients. Health economics and access to prompt diagnosis and treatment are still challenging issues in some Asian regions. The former represents a significant obstacle limiting the access of patients to MPA despite the proven efficacy of the drug as an induction agent and its superiority over azathioprine (AZA) in preventing disease flares when used for long-term maintenance immunosuppression. Calcineurin inhibitors such as tacrolimus deserve further investigation in view of their additional effect on podocytes by reducing proteinuria and the promising data from Asian patients. Despite considerable advances in the clinical management of LN over the past few decades with resultant improvements in patients' outcomes, there are still knowledge gaps and unmet clinical needs. Asia has made substantial contributions to the evidence base that guides clinical management and continues to offer invaluable opportunities for research pursuits.

KEY MESSAGES

Treatment responses and clinical outcomes in Asian patients with LN compare favorably with patients from other parts of the world. The prevention and treatment of infective complications remain significant challenges in managing LN in Asia.

FACTS FROM EAST AND WEST

(1) The prevalence of SLE is lower among Caucasians than other ethnicities. A higher prevalence is observed among Asians and African Americans, while the highest prevalence is found in Caribbean people. The prevalence of LN in Asian SLE patients is much higher than in Caucasians as well. However, the 10-year renal outcome and renal survival rate appear to be better in Asians. (2) Polymorphisms of genes involved in the immune response, such as Fcγ receptor, integrin alpha M, TNF superfamily 4, myotubularin-related protein 3 and many others, might be partly responsible for the differences in prevalence between the different ethnic groups. European ancestry was shown to be associated with a decrease in the risk of LN even after adjustment for genes most associated with renal disease. (3) Access to health care is a key determinant of disease progression, treatment outcome and the management of complications such as infections, particularly in South Asia, and might also explain disparities between clinical outcomes. (4) The efficacy of low-dose CYC combined with corticosteroids for induction treatment of LN was proved in European Caucasian patients. This treatment is also used in Asia, although no formal evaluation of efficacy and safety in comparison with other treatment regimens exists in this population. The efficacy of mycophenolate mofetil (MMF) is similar to that of CYC, and similar between Asians and Caucasians. MMF may be more effective than CYC in inducing response in high-risk populations such as African American or Hispanic patients. MMF might cause less infection-related events in Asians, but its high cost prevents broader usage at present. (5) For maintenance therapy, corticosteroid combined with AZA or MMF is used worldwide, with a broadly similar efficacy of both treatments, although there are data suggesting that in high-risk populations (e.g. African Americans) MMF may be more effective in preventing renal flares. AZA is often preferred in Asia due to economic constraints and because of its safety in pregnancy. (6) Alternative therapies under investigation include rituximab, which might be more efficient in Caucasians, as well as belimumab. Recent Japanese and Chinese studies have indicated a potential benefit of tacrolimus as a substitute for or in addition to CYC or MMF (dual or triple immunosuppression). Mizoribine is used in Japan exclusively.

Association of FCGR3A and FCGR3B copy number variations with systemic lupus erythematosus and rheumatoid arthritis in Taiwanese patients

Objective

To determine whether copy number variations (CNVs) in FCGR3A and FCGR3B are associated with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in Taiwanese individuals.

Methods

FCGR3A and FCGR3B CNV genotypes were determined in 846 patients with SLE, 948 patients with RA, and 1,420 healthy control subjects, using custom TaqMan CNV assays. The FCGR3A and FCGR3B CNV genotypes were compared between healthy control subjects and patients and among patients stratified according to clinical characteristics.

Results

A low (<2) FCGR3A copy number was significantly associated with SLE (for <2 copies versus 2 copies, P = 5.06 × 10⁻⁴, false discovery rate–corrected P [P_FDR] = 0.001, odds ratio [OR] 3.26, 95% confidence interval [95% CI] 1.68−6.35) and RA (for <2 copies versus 2 copies, P = 5.83 × 10⁻⁴, P_FDR = 0.0012, OR 2.82, 95% CI 1.56−5.1). A low FCGR3B copy number was also significantly associated with SLE (for <2 copies versus 2 copies, P = 0.0032, P_FDR = 0.0032, OR 1.59, 95% CI 1.17−2.18). Notably, a high (>2) FCGR3A copy number was also associated with SLE (for >2 copies versus 2 copies, P = 0.003, P_FDR = 0.0061, OR 1.6, 95% CI 1.17−2.18). Additionally, the FCGR3A low copy number genotype was significantly enriched in subsets of patients with SLE (those with ulcer, arthritis, rash, discoid rash, photosensitivity, nephritis, leukopenia, thrombocytopenia, depressed complement levels, and autoantibody positivity) and patients with RA (those positive for rheumatoid factor) compared with healthy control subjects. The FCGR3B low copy number genotype was also significantly enriched in SLE patients with ulcer, rash, discoid rash, photosensitivity, ascites, nephritis, complement level depression, and anti–double-stranded DNA antibody positivity compared with control subjects. However, FCGR3B CNVs were not associated with RA susceptibility (for <2 copy numbers versus 2 copy numbers, P = 0.3584, OR 1.15, 95% CI 0.85–1.55) and clinical characteristics.

Conclusion

In Taiwanese individuals, a low FCGR3A copy number is a common risk factor for SLE and RA, while a low FCGR3B copy number confers a risk of SLE but not RA.

Fcγ receptor IIIa single-nucleotide polymorphisms and haplotypes affect human IgG binding and are associated with lupus nephritis in African Americans

OBJECTIVE

To investigate whether the Fcγ receptor IIIa-66L/R/H (FcγRIIIa-66L/R/H) polymorphism influences net effective receptor function and to assess if the FCGR3A combined genotypes formed by FcγRIIIa-66L/R/H and FcγRIIIa-176F/V, as well as copy number variation (CNV), confer risk of developing systemic lupus erythematosus (SLE) and lupus nephritis.

METHODS

FcγRIIIa variants, expressed on A20 IIA1.6 cells, were used in flow cytometry-based human IgG-binding assays. Using Pyrosequencing methodology, FCGR3A single-nucleotide polymorphism and CNV genotypes were determined in a cohort of 1,728 SLE patients and 2,404 healthy controls.

RESULTS

The FcγRIIIa-66L/R/H (rs10127939) polymorphism influenced ligand binding capacity in the presence of the FcγRIIIa-176V (rs396991) allele. There was a trend toward an association of the low-binding FcγRIIIa-176F allele with lupus nephritis among African Americans (P = 0.0609) but not among European Americans (P > 0.10). Nephritis among African American patients with SLE was associated with FcγRIIIa low-binding haplotypes containing the 66L/R/H and 176F variants (P = 0.03) and with low-binding genotype combinations (P = 0.002). No association was observed among European American patients with SLE. The distribution of FCGR3A CNV was not significantly different among controls and SLE patients with or without nephritis.

CONCLUSION

FcγRIIIa-66L/R/H influences ligand binding. The low-binding haplotypes formed by 66L/R/H and 176F confer enhanced risk of lupus nephritis in African Americans. FCGR3A CNVs are not associated with SLE or lupus nephritis in either African Americans or European Americans.

Asian ethnicity in systemic lupus erythematosus: an Australian perspective

Ethnic differences in both disease susceptibility and expression have been noted in systemic lupus erythematosus (SLE). This review focuses on the evidence of disparities between SLE patients of Asian and Caucasian descent, the two predominant ethnic groups affected by SLE in the Australian context. While epidemiological studies suggest higher rates of SLE among Asian patients, multi-ethnic cohort studies have allowed direct comparison of disease characteristics between different ethnic groups. Such studies suggest that Asians are affected by more severe SLE across several disease parameters, including increased renal involvement, autoantibody positivity, disease activity and damage accumulation. As delineation of these disparities becomes clearer, uncovering the biological basis of such differences poses a significant opportunity to progress understanding of SLE pathogenesis. Understanding ethnic variation in disease provides a platform for an individualised approach to risk assessment, monitoring and management of SLE.

Association of Asian ethnicity with disease activity in SLE: an observational study from the Monash Lupus Clinic

OBJECTIVE

Systemic lupus erythematosus (SLE), an autoimmune condition with diverse clinical manifestations, is reported to have different expression in populations of different ancestry. Most previous studies compared patients of different ethnic groups from geographically distinct cohorts. In our study, we aimed to characterize disease manifestations in patients of different ethnic groups from a single centre, and studied patterns of disease activity over time.

METHODS

Demographics, baseline disease characteristics and autoantibody profiles, and disease activity (SLEDAI) measured at each visit, were captured from all consenting patients prospectively followed between 2007 and 2011 in an urban teaching hospital lupus clinic. Ethnicity was self-reported.

RESULTS

Asian ethnicity was significantly associated with more clinically severe SLE. Time-adjusted mean SLEDAI (p = 0.01) and maximum SLEDAI (p = 0.0018) were significantly higher in Asian patients. Asians were more likely to have renal disease (OR 2.9, 95% CI 1.4-5.98; p = 0.004) and persistently active disease (PAD) (OR 2.14, 95% CI 1.05-4.38, p = 0.04). Asian lupus patients also had a significantly higher proportion of autoantibody positivity to anti-dsDNA, anti-RNP, anti-Sm, anti-Ro and anti-La, as well as increased likelihood of hypocomplementaemia and immunosuppressant use.

CONCLUSION

In this single-cohort study, Asian ethnicity was found to be associated with increased SLE disease activity. This suggests significant inter-ethnic genetic contributions to the regulation of autoimmune responses and disease severity in SLE.

Biomarker profiling for lupus nephritis

Lupus nephritis (LN) is one of the most severe manifestations of systemic lupus erythematosus (SLE), which is associated with significant morbidity and mortality of SLE patients. The pathogenesis of LN involves multiple factors, including genetic predisposition, epigenetic regulation and environmental interaction. Over the last decade, omics-based techniques have been extensively utilized for biomarker screening and a wide variety of variations which are associated with SLE and LN have been identified at the levels of genomics, transcriptomics and proteomics. These studies and discoveries have expanded our understanding of the molecular basis of the disease and are important for identification of potential therapeutic targets for disease prediction and early treatment. In this review, we summarize some of the recent studies targeted at the identification of LN-associated biomarkers using genomics and proteomic approaches.

Lupus nephritis: a critical review

Lupus nephritis remains one of the most severe manifestations of systemic lupus erythematosus associated with considerable morbidity and mortality. A better understanding of the pathogenesis of lupus nephritis is an important step in identifying more targeted and less toxic therapeutic approaches. Substantial research has helped define the pathogenetic mechanisms of renal manifestations and, in particular, the complex role of type I interferons is increasingly recognized; new insights have been gained into the contribution of immune complexes containing endogenous RNA and DNA in triggering the production of type I interferons by dendritic cells via activation of endosomal toll-like receptors. At the same time, there have been considerable advances in the treatment of lupus nephritis. Corticosteroids have long been the cornerstone of therapy, and the addition of cyclophosphamide has contributed to renal function preservation in patients with severe proliferative glomerulonephritis, though at the cost of serious adverse events. More recently, in an effort to minimize drug toxicity and achieve equal effectiveness, other immunosuppressive agents, including mycophenolate mofetil, have been introduced. Herein, we provide a detailed review of the trials that established the equivalency of these agents in the induction and/or maintenance therapy of lupus nephritis, culminating in the recent publication of new treatment guidelines by the American College of Rheumatology. Although newer biologics have been approved and continue to be a focus of research, they have, for the most part, been relatively disappointing compared to the effectiveness of biologics in other autoimmune diseases. Early diagnosis and treatment are essential for renal preservation.

Replicated associations of TNFAIP3, TNIP1 and ETS1 with systemic lupus erythematosus in a southwestern Chinese population

Introduction

Recent genome-wide and candidate gene association studies in large numbers of systemic lupus erythematosus (SLE) patients have suggested approximately 30 susceptibility genes. These genes are involved in three types of biological processes, including immune complex processing, toll-like receptor function and type I interferon production, and immune signal transduction in lymphocytes, and they may contribute to the pathogenesis of SLE. To better understand the genetic risk factors of SLE, we investigated the associations of seven SLE susceptibility genes in a Chinese population, including FCGR3A, FCGR2A, TNFAIP3, TLR9, TREX1, ETS1 and TNIP1.

Methods

A total of 20 SNPs spanning the seven SLE susceptibility genes were genotyped in a sample of 564 unrelated SLE patients and 504 unrelated healthy controls recruited from Yunnan, southwestern China. The associations of SNPs with SLE were assessed by statistical analysis.

Results

Five SNPs in two genes (TNFAIP3 and ETS1) were significantly associated with SLE (corrected P values ranging from 0.03 to 5.5 × 10^-7). Through stratified analysis, TNFAIP3 and ETS1 showed significant associations with multiple SLE subphenotypes (such as malar rash, arthritis, hematologic disorder and antinuclear antibody) while TNIP1 just showed relatively weak association with onset age. The associations of the SNPs in the other four genes were not replicated.

Conclusions

The replication analysis indicates that TNFAIP3, ETS1 and TNIP1 are probably common susceptibility genes for SLE in Chinese populations, and they may contribute to the pathogenesis of multiple SLE subphenotypes.

Do Asian patients have worse lupus?

The predisposition to and clinical phenotype of systemic lupus erythematosus, an autoimmune disease that is associated with significant morbidity and mortality, are affected by genetic and environmental factors. This article aims to examine whether Asians have worse lupus by reviewing the literature on genetic predisposition and clinical outcomes, including major organ involvement, damage score and mortality in Asian populations compared with other ethnicities. A number of lupus nephritis susceptibility genes have been identified in Asians and White patients, with further variations among different Asian populations. Meta-analysis studies on various Fcγ receptor subtypes revealed that FcγRIIIA-F158 allele, which is associated with low binding affinity to IgG1 and IgG3, predisposed to lupus nephritis in Asian patients. Asian patients were reported to have higher rates of lupus nephritis-associated autoantibodies, lupus nephritis and more active glomerulonephritis compared with White patients. Renal outcome and the level of immunosuppressant use in Asians were comparable to Afro-American Blacks in some studies. Asians were also found to have higher overall damage scores compared with Whites. The difference in mortality between Asian patients and other ethnicities in different geographical regions was found to vary depending on socioeconomic factors such as access to health care. Poverty, education level, cultural and behavioural factors are confounders to ethnicity in determining clinical outcome of systemic lupus erythematosus.

Genetic variation of the Fc gamma receptor 3B gene and association with rheumatoid arthritis

Background

Fc gamma receptors (FcγRs) play a crucial role in immunity by linking IgG antibody-mediated responses with cellular effector and regulatory functions. Genetic variants in these receptors have been previously identified as risk factors for several chronic inflammatory conditions. The present study aimed to investigate the presence of copy number variations (CNVs) in the FCGR3B gene and its potential association with the autoimmune disease rheumatoid arthritis (RA).

Methodology/Principal Findings

CNV of the FCGR3B gene was studied using Multiplex Ligation Dependent Probe Amplification (MLPA) in 518 Dutch RA patients and 304 healthy controls. Surprisingly, three independent MLPA probes targeting the FCGR3B promoter measured different CNV frequencies, with probe#1 and #2 measuring 0 to 5 gene copies and probe#3 showing little evidence of CNV. Quantitative-PCR correlated with the copy number results from MLPA probe#2, which detected low copy number (1 copy) in 6.7% and high copy number (≥3 copies) in 9.4% of the control population. No significant difference was observed between RA patients and the healthy controls, neither in the low copy nor the high copy number groups (p-values = 0.36 and 0.71, respectively). Sequencing of the FCGR3B promoter region revealed an insertion/deletion (indel) that explained the disparate CNV results of MLPA probe#1. Finally, a non-significant trend was found between the novel -256A>TG indel and RA (40.7% in healthy controls versus 35.9% in RA patients; P = 0.08).

Conclusions/Significance

The current study highlights the complexity and poor characterization of the FCGR3B gene sequence, indicating that the design and interpretation of genotyping assays based on specific probe sequences must be performed with caution. Nonetheless, we confirmed the presence of CNV and identified novel polymorphisms in the FCGR3B gene in the Dutch population. Although no association was found between RA and FCGR3B CNV, the possible protective effect of the -256A>TG indel polymorphism must be addressed in larger studies.