Implication of IL-2/IL-21 region in systemic sclerosis genetic susceptibility

Role of IL-2/IL-2 receptor in pathogenesis of autoimmune disorders: Genetic and therapeutic aspects

Interleukin-2 (IL-2) is an important cytokine that plays a key role in the immune response. The IL-2 receptor (IL-2R) is composed of three subunits, alpha, beta, and gamma, with the alpha subunit having the highest affinity for IL-2. Several studies reported that immune dysregulation of IL-2 may cause tissue injury as well as damage leading to the pathogenesis of various autoimmune diseases such as acute necrotizing vasculitis in systemic lupus erythematosus (SLE), inflammatory synovitis in rheumatoid arthritis (RA), salivary and lacrimal gland dys-function in Sjogren syndrome (SS), obliterative vasculopathy fibrosis in systemic sclerosis (SSc), and inflammatory demyelination in multiple sclerosis (MS). The aim of this review paper was to examine the role of IL-2/IL-2R in various autoimmune disorders, taking into account recent advancements and discoveries, gaps in the current literature, ongoing debates, and potential avenues for future research. The focus of this review is on systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, sjogren syndrome, and multiple sclerosis, which are all linked to the malfunctioning of IL-2/IL-2R. In genetic studies, gene polymorphisms of IL-2 such as IL-2 330/T, IL-2 330/G, and rs2069763 are involved in increasing the risk of SLE. Furthermore, genetic associations of IL-2/IL-2R such as rs791588, rs2281089, rs2104286, rs11594656, and rs35285258 are significantly associated with RA susceptibility. The IL-2 polymorphism including rs2069762A, rs6822844T, rs6835457G, and rs907715T are significant connections with systemic sclerosis. In addition, rs2104286 (IL-2), rs11594656 (IL-2RA), rs35285258 (IL-2RB) gene polymorphism significant increases the risk of multiple sclerosis. In therapeutic approaches, low-dose IL-2 therapy could regulate Tfr and Tfh cells, resulting in a reduction in disease activity in the SLE patients. In addition, elevated sIL-2R levels in the peripheral blood of SLE patients could be linked to an immunoregulatory imbalance, which may contribute to the onset and progression of SLE. Consequently, sIL-2R could potentially be a target for future SLE therapy. Moreover, Low dose-IL2 was well-tolerated, and low levels of Treg and high levels of IL-21 were associated with positive responses to Ld-IL2 suggested to be a safe and effective treatment for RA. Additionally, low-dose IL-2 treatment improves the exocrine glands' ability to secrete saliva in SS-affected mice. Whereas, Basiliximab targets the alpha chain of the IL-2 receptor suggested as a potential treatment for SSc. Also, pre-and post-treatment with Tregs, MDSCs, and IL-2 may have the potential to prevent EAE induction in patients with MS. It is suggested that further studies should be conducted on IL-2 polymorphism in Sjogren syndrome.

Determination of T Cell Responses in Thai Systemic Sclerosis Patients

Objectives

This study is aimed at determining the role of T cells by assessing the numbers of IFN-γ- and IL-2-secreting T cells following stimulation with peptides derived from DNA topoisomerase-I protein in Thai SSc patients.

Methods

Fifty Thai SSc patients and 50 healthy controls (HC) joined this study. IFN-γ and IL-2 levels upon stimulation of T cells with 6 peptides derived from DNA topoisomerase-I protein were determined. Anti-nuclear antibodies (ANA) and anti-Scl-70 antibodies were determined by using the ELISA method.

Results

In SSc patients, we detected a significantly higher number of IFN-γ- and IL-2-secreting CD8⁺ T cells than IFN-γ- and IL-2-secreting CD4⁺ T cells after stimulation with pooled peptides derived from DNA topoisomerase-I protein. A similar percentage of CD4⁺IL-2⁺, CD4⁺IFN-γ⁺, and CD8⁺IL-2⁺ were detected following stimulation with DNA topoisomerase-I protein -in SSc patients with anti-Scl-70 antibody (SSc/anti-Scl-70⁺) and those without. In contrast, the amount of CD8⁺IFN-γ⁺ cells was significantly higher in SSc/anti-Scl-70⁺ than those without. Stimulation with individual peptides showed that CSLRVEHINLHPELD (sPep3; 15 amino acids; position 505-519 of DNA topoisomerase-I protein) was the optimal epitope that induced T cells secreting the highest levels of IFN-γ and IL-2. A higher percentage of IFN-γ⁺CD4⁺ T cells was detected in SSc/anti-Scl-70⁺ than those without the following stimulation with peptides 2 (amino acid position 475-486 [RAVALYFIDKLA] of protein DNA topoisomerase).

Conclusion

The results from this study emphasize the critical role of DNA topoisomerase-I peptides on the activation of T cells in SSc patients. The findings provide a better understanding of SSc's immunopathogenesis and may lead to the development of diagnostic tools and specific treatments for SSc in the future.

Impact of IL-21 Gene Polymorphisms (rs2055979) and the Levels of Serum IL-21 on the Risk of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system. Genetic and environmental factors have important roles in the induction, onset, and progression of MS. In this study, the IL-21 genotype (rs2055979) (G/T) in Iraqi MS patients was compared with a healthy control group to investigate the possible association of any particular genotype or allele with multiple sclerosis. This study included 70 patients with relapsing-remitting MS and 50 healthy individuals as control. Following the extraction of genomic DNA, polymerase chain reaction-restriction fragment length polymorphism, the frequencies of genotypes, and alleles were calculated and statistically analyzed. The results of the study revealed a significant reduction in the distribution of the wild homozygous genotype (GG) in MS patients, in comparison to a healthy control group (14.3% vs. 34 %; 0.0129 at P≤0.05; odds ratio [OR] 3.0909, 95% confidence interval [CI]: 1.2704-7.5203). However, MS cases and controls did not differ significantly in neither GT nor TT genotypes, 62.9% (OR 0.6402, 95% CI: 0.3064-1.3374) and 52% (OR 0.5494, 95% CI: 0.2074-1.4557), respectively. The data of allele frequencies in patients and controls showed that the G allele frequencies were 0.46 vs. 0.60 in patients and controls, respectively, while T allele frequencies were 0.54 vs. 0.40 in patients and controls, respectively. The current conclusions indicated that in the study group, the GG genotype of IL-21(rs2055979) could be related to MS.

Involvement of lncRNA IL21-AS1 in interleukin-2 and T follicular regulatory cell activation in systemic lupus erythematosus

BACKGROUND

The single nucleotide polymorphism (SNP) rs62324212, located in IL21 antisense RNA 1 (IL21-AS1), has been identified as a genetic risk variant associated with systemic lupus erythematosus (SLE). We aimed to probe the characteristics of IL21-AS1 and explore its clinical relevance focusing on T helper subsets and disease activity in patients with SLE.

METHODS

rs62324212 genotyping was determined using allelic discrimination by quantitative PCR. Gene expression in peripheral blood mononuclear cells and cell surface markers in CD4⁺ T cells were analyzed using PCR and flow cytometry. The association among IL21-AS1, CD4⁺ T cell subsets, and SLE disease activity was accessed.

RESULTS

Ensembl Genome Browser analysis revealed that rs62324212 (C>A) was located in the predicting enhancer region of IL21-AS1. IL21-AS1 was expressed in the nucleus of CD4⁺ T and B cells, but its expression was decreased in patients with SLE. IL21-AS1 expression was positively correlated with mRNA levels of IL-2 but not IL-21, and it was associated with the proportion of activated T follicular regulatory (Tfr) cells. Furthermore, we observed a significant negative correlation between IL21-AS1 expression and disease activity in patients with SLE (n = 53, p < 0.05).

CONCLUSION

IL21-AS1 has an effect on disease activity through an involvement of IL-2-mediated activation of Tfr cells in SLE. Thus, targeting the IL21-AS1 may provide therapeutic approaches for SLE.

Updates on genetics in systemic sclerosis

Systemic sclerosis (SSc) is a complex disease, in which an interaction of genetic and environmental factors plays an important role in its development and pathogenesis. A number of genetic studies, including candidate gene analysis and genome-wide association study, have found that the associated genetic variants are mainly localized in noncoding regions in the expression quantitative trait locus and influence corresponding gene expression. The gene variants identified as a risk for SSc susceptibility include those associated with innate immunity, adaptive immune response, and cell death, while there are only few SSc-associated genes involved in the fibrotic process or vascular homeostasis. Human leukocyte antigen class II genes are associated with SSc-related autoantibodies rather than SSc itself. Since the pathways between the associated genotype and phenotype are still poorly understood, further investigations using multi-omics technologies are necessary to characterize the complex molecular architecture of SSc, identify biomarkers useful to predict future outcomes and treatment responses, and discover effective drug targets.

Systemic sclerosis pathogenesis: contribution of recent advances in genetics

PURPOSE OF REVIEW

To review susceptibility genes and how they could integrate in systemic sclerosis (SSc) pathophysiology providing insight and perspectives for innovative therapies.

RECENT FINDINGS

SSc is a rare disease characterized by vasculopathy, dysregulated immunity and fibrosis. Genome-Wide association studies and ImmunoChip studies performed in recent years revealed associated genetic variants mainly localized in noncoding regions and mostly affecting the immune system of SSc patients. Gene variants were described in innate immunity (IRF5, IRF7 and TLR2), T and B cells activation (CD247, TNFAIP3, STAT4 and BLK) and NF-κB pathway (TNFAIP3 and TNIP1) confirming previous biological data. In addition to impacting immune response, CSK, DDX6, DNASE1L3 and GSDMA/B could also act in the vascular and fibrotic components of SSc.

SUMMARY

Although genetic studies highlighted the dysregulated immune response in SSc, future research must focus on a deeper characterization of these variants with determination of their functional effects. Moreover, the role of these genes or others on specific vasculopathy and fibrosis would provide insight. Establishment of polygenic score or integrated genome approaches could identify new targets specific of SSc clinical features. This will allow physicians to propose new therapies to SSc patients.

IL-21 gene rs6822844 polymorphism and rheumatoid arthritis susceptibility

Interleukin-21 (IL-21) is a cytokine that plays a crucial role in pathogenesis and activity of the rheumatoid arthritis (RA). Meanwhile, genetic polymorphisms in the IL-21 gene may alter its expression. Previous studies have reported conflicting results assessing the association between the IL-21 rs6822844 G/T polymorphism and RA risk. Thus, it's necessary to perform a meta-analysis to definite above relationship. PubMed database was searched for all papers published until October 20, 2019. Nine case-control studies with 9998 cases and 10742 controls were retrieved based on the search criteria at last. Odds ratio (95% confidence interval) was used to calculate the strength of this association. Publication bias was detected using both Begg's and Egger's tests. Overall, the IL-21 rs6822844 G/T polymorphism was found to be significantly associated with decreased RA risk (e.g. T-allele versus G-allele: OR = 0.81, 95% CI = 0.72-0.91, P < 0.001). In addition, decreased RA risk was also detected both in Asians (eg: TT+TG versus GG: OR = 0.42, 95% CI = 0.31-0.56, P < 0.001) and Caucasians (eg: TT+TG versus GG: OR = 0.85, 95% CI = 0.80-0.91, P < 0.001). A similar trend in association was found in the source of the control and genotype method subgroups. Furthermore, subgroup analysis of rheumatoid factor status revealed a protective relationship between the IL-21 rs6822844 G/T polymorphism and RF+/RF- RA risk. A similar relationship was noted in the anti-citrullinated protein antibody status subgroup. The results of the present study suggest that the IL-21 rs6822844 G/T polymorphism was significantly associated with decreased RA susceptibility.

Diagnostic profiles for precision medicine in systemic sclerosis; stepping forward from single biomarkers towards pathophysiological panels

Systemic sclerosis (SSc) is an autoimmune disease which is characterized by vasculopathy, tissue fibrosis and activation of the innate and adaptive immune system. Clinical features of the disease consists of skin thickening and internal organ involvement. Due to the heterogeneous nature of the disease it is difficult to predict disease progression and complications. Despite the discovery of novel autoantibodies associated with SSc, there is an unmet need for biomarkers for diagnosis, disease progression and response to treatment. To date, the use of single (surrogate) biomarkers for these purposes has been unsuccessful. Combining multiple biomarkers in to predictive panels or ultimately algorithms could be more precise. Given the limited therapeutic options and poor prognosis of many SSc patients, a better understanding of the immune-pathofysiological profiles might aid to an adjusted therapeutic approach. Therefore, we set out to explore immunological fingerprints in various clinically defined forms of SSc. We used multilayer profiling to identify unique immune profiles underlying distinct autoantibody signatures. These immune profiles could fill the unmet need for prognosis and response to therapy in SSc. Here, we present 3 pathophysiological fingerprints in SSc based on the expression of circulating antibodies, vascular markers and immunomodulatory mediators.

The prevalence of systemic sclerosis is increased among patients with alopecia areata: a population-based study

Although the coexistence of alopecia areata (AA) and systemic sclerosis (SSc) has been anecdotally reported, the association between these conditions has been poorly investigated. We aimed to assess the association between AA and SSc using a large-scale real-life computerized database. A cross-sectional study was conducted comparing the prevalence of SSc among patients with AA and among age-, sex-, and ethnicity-matched control subjects. Chi-square and t tests were used for univariate analysis, and logistic regression model was used for multivariate analysis. The study was performed utilizing the computerized database of Clalit Health Services ensuring 4.4 million subjects. A total of 51,561 patients with AA and 51,410 controls were included in the study. The prevalence of SSc was increased in patients with AA as compared with the control group (0.1% vs. 0.0%, respectively; OR, 2.30; 95% CI, 1.2-4.4; P = 0.010). The association was stronger among older and Jewish patients. In a multivariate analysis adjusting for sex, age, ethnicity, and other comorbidities, AA was still independently associated with SSc (OR, 2.3; 95% CI, 1.2-4.4; P = 0.012). In conclusion, a significant positive association was revealed between AA and SSc. Further studies are necessary to establish these findings in other study populations and to elucidate the mechanism underlying this association. Awareness of SSc may be of importance for physicians treating patients with AA, and screening for SSc in patients with relevant symptoms may be considered.

IL-17 and related cytokines involved in systemic sclerosis: Perspectives

Systemic sclerosis (SSc) is a multisystemic, complex, and rare disease of connective tissue, with high morbidity and mortality, and without specific treatment. The disease is characterized by three main principles: vascular disease, autoantibody production and inflammation, and fibrosis. Since it is well defined that SSc is characterized by elevated production of TGF-β, IL-6, and IL-1, all of them cytokines related to Th17 differentiation, the hypothesis is that this disease may be strongly related to a polarization of the immune response towards the Th17 pathway. Considering the importance of a better understanding of the pathophysiology of Th17 pathway in SSc, this article aims to propose an update for a better understanding of current knowledge on main cytokines secreted by the Th17 cells (IL-17 A, IL-21, and IL-22) and the future prospects in the current disease.

Genomic and genetic studies of systemic sclerosis: A systematic review

Systemic sclerosis is an autoimmune rheumatic disease characterised by fibrosis, vasculopathy and inflammation. The exact aetiology of SSc remains unknown but evidences show that various genetic factors may be involved. This review aimed to assess HLA alleles/non-HLA polymorphisms, microsatellites and chromosomal abnormalities that have thus far been associated with SSc. PubMed, Embase and Scopus databases were searched up to July 29, 2015 using a combination of search-terms. Articles retrieved were evaluated based on set exclusion and inclusion criteria. A total of 150 publications passed the filters. HLA and non-HLA studies showed that particular alleles in the HLA-DRB1, HLA-DQB1, HLA-DQA1, HLA-DPB1 genes and variants in STAT4, IRF5 and CD247 are frequently associated with SSc. Non-HLA genes analysis was performed using the PANTHER and STRING₁₀ databases. PANTHER classification revealed that inflammation mediated by chemokine and cytokine, interleukin and integrin signalling pathways are among the common extracted pathways associated with SSc. STRING₁₀ analysis showed that NFKB1, CSF3R, STAT4, IFNG, PRL and ILs are the main "hubs" of interaction network of the non-HLA genes associated with SSc. This study gathers data of valid genetic factors associated with SSc and discusses the possible interactions of implicated molecules.

Genetics of systemic sclerosis: recent advances

Purpose of review

Large-scale and follow-up genetic association studies in systemic sclerosis (SSc) have implicated over 40 regions in disease risk, 15 of which with robust associations. Nevertheless, the causal variants and the functional mechanisms underlying the genetic associations remain elusive, and the reasons for the higher disease burden in African Americans unknown. Incorporating tools from diverse fields is beginning to unveil the role of genetic diversity and regulatory variation in SSc susceptibility. This review will summarize recent advances in SSc genetics, including autoimmune disease overlap, evidence of natural selection, and current progress towards the dissection of the functional role of associated risk variants.

Recent findings

In the past year, multiple large-scale studies reported novel strong and suggestive SSc associations. These results, coupled with the regions shared with other autoimmune diseases, emphasize the role of dysregulation of immune pathways as a key causative factor in SSc pathogenesis. Strong evidence implicates natural selection as a mechanism contributing to the maintenance of some of these SSc alleles in the population. Studies integrating genomic, transcriptomic, and epigenomic datasets in specific cell types to identify causal autoimmune disease variants are emerging.

Summary

The identification and comprehensive understanding of the factors and mechanisms contributing to SSc will contribute to improved diagnosis and disease management.

Current perspectives on the immunopathogenesis of systemic sclerosis

Systemic sclerosis (SSc or scleroderma) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, vasculopathy, and extensive fibrosis. SSc is highly heterogeneous in its clinical presentation, extent and severity of skin and internal organ involvement, and clinical course and has the highest fatality rate among connective tissue diseases. While clinical outcomes have improved in recent years, no current therapy is able to reverse or slow the natural progression of SSc, a reflection of its complex pathogenesis. Although activation of the immune system has long been recognized, the mechanisms responsible for the initiation of autoimmunity and the role of immune effector pathways in the pathogenesis of SSc remain incompletely understood. This review summarizes recent progress in disease pathogenesis with particular focus on the immunopathogenetic mechanisms of SSc.

Identification of an Association of TNFAIP3 Polymorphisms With Matrix Metalloproteinase Expression in Fibroblasts in an Integrative Study of Systemic Sclerosis-Associated Genetic and Environmental Factors

OBJECTIVE

Systemic sclerosis (SSc) is a fibrotic disease attributed to both genetic susceptibility and environmental factors. This study was undertaken to investigate the associations between SSc-associated genetic variants and the expression of extracellular matrix (ECM) genes in human fibroblasts stimulated with silica particles in time-course and dose-response experiments.

METHODS

A total of 200 fibroblast strains were examined for ECM gene expression after stimulation with silica particles. The fibroblasts were genetically profiled using Immunochip assays and then subjected to whole-genome genotype imputation. Associations of genotypes and gene expression were first analyzed in a Caucasian cohort and then validated in a meta-analysis combining the results from Caucasian, African American, and Hispanic subjects. A linear mixed model for longitudinal data analysis was used to identify genetic variants associated with the expression of ECM genes, and the associations were validated by using a haplotype-based longitudinal association test on regions that included the loci identified.

RESULTS

The single-nucleotide polymorphism rs58905141 in TNFAIP3 was consistently associated with time-course and/or dose-response expression of MMP3 and MMP1 in the fibroblasts stimulated with silica particles in both the analysis of Caucasian subjects only and the meta-analysis. Results of the haplotype-based analysis validated the association signals.

CONCLUSION

Our findings indicate that a genetic variant of TNFAIP3 is strongly associated with the silica-induced profibrotic response of fibroblasts. In silico functional analysis based on the ENCODE database revealed that rs58905141 might affect the binding activities of the transcription factors for TNFAIP3. This is the first genome-wide study of interactions between genetic and environmental factors in a complex SSc fibroblast model.

Investigation of IL-21 gene polymorphisms (rs2221903, rs2055979) in cases with multiple sclerosis of Azerbaijan, Northwest Iran

BACKGROUND

Multiple Sclerosis (MS) is a chronic inflammatory demyelinating disease of the Central Nervous System that is immunologically mediated in genetically susceptible individuals. IL-21, a cytokine produced by TCD4(+) cells, particularly by Th-17 cells, is believed to play an important role in the MS pathogenesis.

OBJECTIVE

This study was performed to investigate the impact of genetic polymorphisms in IL-21 gene on MS susceptibility and clinical profiles.

METHODS

Seventy Iranian patients with clinically definite relapsing-remitting MS and 110 age, sex and ethic matched controls were genotyped for IL-21 gene polymorphisms using PCR-RFLP method.

RESULTS

Our results showed that the IL-21 rs2221903 SNP is not polymorphic in our population. Also, the allelic and genotypic frequencies of the IL-21 rs2055979 did not differ significantly between the MS patients and controls (P = 0.413 and P = 0.565 respectively, and OR = 1.122, 95% CI = 0.79-1.87 for T allele). However, our results showed that IL-21 rs2055979 (G/T) T allele positive (TT+GT) MS patients had lower (PI ≤ 1.5) disease progression compared to rs2055979 T allele negative (GG) patients (P = 0.009).

CONCLUSION

Our results showed that no outstanding association exists between IL-21 alleles and susceptibility to MS. However, our clinical analysis showed significant association of IL-21 gene polymorphism with the progression of multiple sclerosis disease. Our results indicate that the G allele promotes, or the T allele protects against disease progression. To clarify the role of IL-21 rs2055979 in MS pathogenesis, further comprehensive studies with larger sample sizes among different ethnicity populations are recommended.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Fecal stream diversion and mucosal cytokine levels in collagenous colitis: A case report

In this case report, we examined the levels of cytokines expressed before and during fecal stream diversion and after intestinal continuity was restored in a patient with collagenous colitis. We report the case of a 46-year-old woman with chronic, active collagenous colitis who either failed to achieve clinical remission or experienced adverse effects with the following drugs: loperamide, cholestyramine, budesonide, methotrexate and adalimumab. Due to the intractable nature of the disease and because the patient was having up to 15 watery bowel movements per day, she underwent a temporary ileostomy. Colonic biopsies were analyzed for mucosal cytokine protein levels before and during fecal stream diversion and after intestinal continuity was restored. Mucosal protein levels of interleukin (IL)-1β, IL-2, IL-6, IL-12, IL-17 A, IL-23, TNF, IFN-γ, IL-4, IL-5, IL-10 and IL-13 were all higher during active disease and decreased to non-detectable or considerably lower levels during fecal stream diversion. One month after the restoration of bowel continuity, when the patient experienced a relapse of symptoms, IL-2, IL-23 and IL-21 levels were again increased. Our results indicate that fecal stream diversion in this patient suppressed the levels of all cytokines analyzed in colonic biopsies. With the recurrence of clinical symptoms and histological changes after bowel reconstruction, the levels of primarily proinflammatory cytokines increased. Our findings support the hypothesis that a luminal factor triggers the inflammation observed in collagenous colitis.

Genetics, Epigenetics, and Genomics of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease that occurs in a genetically susceptible host. Genetic studies performed so far reveal that multiple genetic loci contribute to disease susceptibility in SSc. The purpose of this review is to discuss the current knowledge of genetics in SSc by exploring the observational evidence, the different genetic studies, and their modalities as well as the most relevant genes discovered by these. The importance of gene expression variation and the different mechanisms that govern it, including the recently discovered field of epigenetics, are also explored, with an emphasis on microRNA.

Systems level analysis of systemic sclerosis shows a network of immune and profibrotic pathways connected with genetic polymorphisms

Systemic sclerosis (SSc) is a rare systemic autoimmune disease characterized by skin and organ fibrosis. The pathogenesis of SSc and its progression are poorly understood. The SSc intrinsic gene expression subsets (inflammatory, fibroproliferative, normal-like, and limited) are observed in multiple clinical cohorts of patients with SSc. Analysis of longitudinal skin biopsies suggests that a patient's subset assignment is stable over 6-12 months. Genetically, SSc is multi-factorial with many genetic risk loci for SSc generally and for specific clinical manifestations. Here we identify the genes consistently associated with the intrinsic subsets across three independent cohorts, show the relationship between these genes using a gene-gene interaction network, and place the genetic risk loci in the context of the intrinsic subsets. To identify gene expression modules common to three independent datasets from three different clinical centers, we developed a consensus clustering procedure based on mutual information of partitions, an information theory concept, and performed a meta-analysis of these genome-wide gene expression datasets. We created a gene-gene interaction network of the conserved molecular features across the intrinsic subsets and analyzed their connections with SSc-associated genetic polymorphisms. The network is composed of distinct, but interconnected, components related to interferon activation, M2 macrophages, adaptive immunity, extracellular matrix remodeling, and cell proliferation. The network shows extensive connections between the inflammatory- and fibroproliferative-specific genes. The network also shows connections between these subset-specific genes and 30 SSc-associated polymorphic genes including STAT4, BLK, IRF7, NOTCH4, PLAUR, CSK, IRAK1, and several human leukocyte antigen (HLA) genes. Our analyses suggest that the gene expression changes underlying the SSc subsets may be long-lived, but mechanistically interconnected and related to a patients underlying genetic risk.

Systemic Sclerosis is a Complex Disease Associated Mainly with Immune Regulatory and Inflammatory Genes

Systemic sclerosis (SSc) is a fibrotic and autoimmune disease characterized clinically by skin and internal organ fibrosis and vascular damage, and serologically by the presence of circulating autoantibodies. Although etiopathogenesis is not yet well understood, the results of numerous genetic association studies support genetic contributions as an important factor to SSc. In this paper, the major genes of SSc are reviewed. The most recent genome-wide association studies (GWAS) are taken into account along with robust candidate gene studies. The literature search was performed on genetic association studies of SSc in PubMed between January 2000 and March 2014 while eligible studies generally had over 600 total participants with replication. A few genetic association studies with related functional changes in SSc patients were also included. A total of forty seven genes or specific genetic regions were reported to be associated with SSc, although some are controversial. These genes include HLA genes, STAT4, CD247, TBX21, PTPN22, TNFSF4, IL23R, IL2RA, IL-21, SCHIP1/IL12A, CD226, BANK1, C8orf13-BLK, PLD4, TLR-2, NLRP1, ATG5, IRF5, IRF8, TNFAIP3, IRAK1, NFKB1, TNIP1, FAS, MIF, HGF, OPN, IL-6, CXCL8, CCR6, CTGF, ITGAM, CAV1, MECP2, SOX5, JAZF1, DNASEIL3, XRCC1, XRCC4, PXK, CSK, GRB10, NOTCH4, RHOB, KIAA0319, PSD3 and PSOR1C1. These genes encode proteins mainly involved in immune regulation and inflammation, and some of them function in transcription, kinase activity, DNA cleavage and repair. The discovery of various SSc-associated genes is important in understanding the genetics of SSc and potential pathogenesis that contribute to the development of this disease.

Association of IL-21 polymorphisms (rs907715, rs2221903) with susceptibility to multiple autoimmune diseases: a meta-analysis

OBJECTIVES

Previous published data indicated that interleukin-21 (IL-21) gene polymorphisms were shown to associate with multiple autoimmune diseases (ADs), but the results remain inconclusive. The aim of this study was to perform a meta-analysis to assess the overall association between IL-21 gene polymorphisms (rs907715, rs2221903) and multiple ADs.

METHODS

All eligible case-control studies were searched in the PubMed and Embase database. A meta-analysis was conducted on the association between the IL-21 gene variants and ADs using: (1) allelic contrast, (2) homozygote contrast, (3) the recessive model, and (4) the dominant model.

RESULTS

A total of 12 relevant studies including 10,535 cases and 19,356 controls were enrolled in this meta-analysis. A significant association between IL-21 rs907715 gene polymorphism and AD was found under the allelic (OR: 1.102, 95% CI: 1.057-1.149, p = 0.000), homozygous (OR: 1.220, 95% CI: 1.089-1.368, p = 0.001), dominant (OR: 1.160, 95% CI: 1.027-1.309, p = 0.017), and recessive genetic model (OR: 1.119, 95% CI: 1.055-1.187, p = 0.000) among Caucasian populations. However, there was no significant association between IL-21 rs2221903 polymorphism and AD in different genetic models.

CONCLUSIONS

Data from the present study suggest that the IL-21 rs907715 polymorphism might be associated with multiple ADs susceptibility in Caucasians. Especially, the allele G of intronic rs907715 in IL-21 confers increased risk of ADs.

Genetic association of IL-21 polymorphisms with dilated cardiomyopathy in a Han Chinese population

BACKGROUND

Autoimmune abnormalities appear to be major predisposing factors for dilated cardiomyopathy (DCM). Interleukin-21 (IL-21) gene polymorphisms have been previously found to be associated with autoimmune diseases. This study aimed to assess the role of IL-21 in DCM in a Han Chinese population.

PATIENTS AND METHODS

A total of 364 independent DCM patients and 384 unrelated healthy controls were recruited for this case-control association study. rs2055979 and rs12508721 were genotyped by PCR-RFLP. IL-21 plasma levels in samples from DCM and control individuals were evaluated by ELISA. The association between the SNPs and overall survival (OS) was evaluated by Kaplan-Meier analysis. Hazard ratios and 95 % confidence intervals (CIs) were assessed in a Cox regression analysis with adjustment for sex and age.

RESULTS

The T allele frequencies of both SNPs were higher in DCM patients than in controls (p < 0.001). The genotypic frequencies of rs2055979 G > T and rs12508721 C > T were associated with DCM in the codominant, dominant, and recessive models (p < 0.05). IL-21 plasma levels in patients were higher than those of the control subjects (p = 0.009). The TT genotypes of both SNPs were associated with significantly higher plasma levels (prs2055979 = 0.03, prs12508721 < 0.001). Kaplan-Meier analysis showed that the genotypic frequencies of both SNPs were associated with OS in the dominant and the recessive models (p < 0.001). The TT genotypes of both SNPs were associated with the worst OS (p < 0.001).

CONCLUSION

Our findings suggest that theIL-21 gene plays an important role in susceptibility to DCM as well as in the clinical outcome of this ailment in the Han Chinese population.