Evaluation of genetic association between an ITGAM non-synonymous SNP (rs1143679) and multiple autoimmune diseases

Exploring the contribution of genetics on the clinical manifestations of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by diverse clinical manifestations affecting multiple organs and systems. The understanding of genetic factors underlying the various manifestations of SLE has evolved considerably in recent years. This review provides an overview of the genetic implications in some of the most prevalent manifestations of SLE, including renal involvement, neuropsychiatric, cutaneous, constitutional, musculoskeletal, and cardiovascular manifestations. We discuss the current state of knowledge regarding the genetic basis of these manifestations, highlighting key genetic variants and pathways implicated in their pathogenesis. Additionally, we explore the clinical implications of genetic findings, including their potential role in risk stratification, prognosis, and personalized treatment approaches for patients with SLE. Through a comprehensive examination of the genetic landscape of SLE manifestations, this review aims to provide insights into the underlying mechanisms driving disease heterogeneity and inform future research directions in this field.

Identification of coagulation-related genes as potential diagnostic biomarkers for pediatric septic shock

This study aimed to identify important clotting associated genes (CRGs) associated with septic shock in children and explore possible important mechanisms of the disease. Five hub genes with diagnostic performance were identified using GEO database and data from literature. These hub genes have strong correlation with immune cells. ceRNA network was constructed to explore potential pathogenic mechanisms. Ten candidate small molecule compounds were identified. In summary, the hub genes may play an important role in the immunity and disease development of septic shock, providing new ideas and strategies for future diagnosis and mechanism evaluation of children with septic shock.

Exploring the shared biomarkers between cardioembolic stroke and atrial fibrillation by WGCNA and machine learning

Background

Cardioembolic Stroke (CS) and Atrial Fibrillation (AF) are prevalent diseases that significantly impact the quality of life and impose considerable financial burdens on society. Despite increasing evidence of a significant association between the two diseases, their complex interactions remain inadequately understood. We conducted bioinformatics analysis and employed machine learning techniques to investigate potential shared biomarkers between CS and AF.

Methods

We retrieved the CS and AF datasets from the Gene Expression Omnibus (GEO) database and applied Weighted Gene Co-Expression Network Analysis (WGCNA) to develop co-expression networks aimed at identifying pivotal modules. Next, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis on the shared genes within the modules related to CS and AF. The STRING database was used to build a protein-protein interaction (PPI) network, facilitating the discovery of hub genes within the network. Finally, several common used machine learning approaches were applied to construct the clinical predictive model of CS and AF. ROC curve analysis to evaluate the diagnostic value of the identified biomarkers for AF and CS.

Results

Functional enrichment analysis indicated that pathways intrinsic to the immune response may be significantly involved in CS and AF. PPI network analysis identified a potential association of 4 key genes with both CS and AF, specifically PIK3R1, ITGAM, FOS, and TLR4.

Conclusion

In our study, we utilized WGCNA, PPI network analysis, and machine learning to identify four hub genes significantly associated with CS and AF. Functional annotation outcomes revealed that inherent pathways related to the immune response connected to the recognized genes might could pave the way for further research on the etiological mechanisms and therapeutic targets for CS and AF.

CD11b suppresses TLR7-driven inflammatory signaling to protect against lupus nephritis

Lupus Nephritis (LN) is a severe complication of systemic lupus erythematosus (SLE) that affects kidney function. Here, we investigated the role of CD11b, a protein encoded by the ITGAM gene, in the development of LN and its functional activation as a therapeutic strategy. Genetic coding variants of ITGAM significantly increase the risk for SLE and LN by producing a less active CD11b and leading to elevated levels of type I interferon (IFN I). However, a molecular mechanism for how these variants increase LN risk has been unclear. Here, we determined that these variants also significantly associate with elevations in soluble urokinase plasminogen activator receptor (suPAR), a known biomarker linked to kidney disease, suggesting a novel molecular connection. Pharmacologic activation of CD11b with a novel, clinical-stage agonist ONT01 significantly suppressed suPAR production in myeloid cells and reduced systemic inflammation and kidney damage in multiple experimental models of LN. Importantly, delaying treatment with ONT01 until after disease onset also significantly reduced serum suPAR and inflammatory cytokines, and decreased immune complex deposition in the glomerulus, glomerulonephritis and albuminuria, suggesting that CD11b activation is therapeutic for LN. Genetic activation of CD11b via a gain-of-function CD11b mutation also showed complete protection from LN, whereas genetic deletion of CD11b worsened the disease in mice, providing further evidence of the role of CD11b activation in regulating LN. Finally, transfer of human LN PBMCs generated human LN like disease in mice that was significantly reduced by ONT01. Together, these data provide strong evidence that ONT01 mediated CD11b activation can therapeutically modulate TLR7-driven inflammation and protect against LN. These findings support clinical development of CD11b agonists as novel therapeutics for treating lupus nephritis in human patients.

Biomimetic design of fibril-forming non-immunogenic collagen like proteins for tissue engineering

Collagen, a key component of extracellular matrix serves as a linchpin for maintaining structural integrity and functional resilience. Concerns over purity and immunogenicity of animal-derived collagens have spurred efforts to develop synthetic collagen-based biomaterials. Despite several collagen mimics, there remains limited exploration of non-immunogenic biomaterials with the capacity for effective self-assembly. To combat the lacuna, collagen like protein (CLP) variants were rationally designed and recombinantly expressed, incorporating human telopeptide sequences (CLP-N and CLP-NC) and bioactive binding sites (CLP-NB). Circular dichroism analyses of the variants confirmed the triple helical conformation, with variations in thermal stability and conformation attributed to the presence of telopeptides at one or both ends of CLP. The variants had propensity to form oligomers, setting the stage for fibrillogenesis. The CLP variants were biocompatible, hemocompatible and supported cell proliferation and migration, particularly CLP-NB with integrin-binding sites. Gene expression indicated a lack of significant upregulation of inflammatory markers, highlighting the non-immunogenic nature of these variants. Lyophilized CLP scaffolds maintained their triple-helical structure and offered favorable biomaterial characteristics. These results accentuate the potential of designed CLP variants in tissue engineering, regenerative medicine and industrial sectors, supporting the development of biocompatible scaffolds and implants for therapeutic and cosmetic purposes.

Integrins in Health and Disease-Suitable Targets for Treatment?

Integrin receptors are heterodimeric surface receptors that play multiple roles regarding cell-cell communication, signaling, and migration. The four members of the β2 integrin subfamily are composed of an alternative α (CD11a-d) subunit, which determines the specific receptor properties, and a constant β (CD18) subunit. This review aims to present insight into the multiple immunological roles of integrin receptors, with a focus on β2 integrins that are specifically expressed by leukocytes. The pathophysiological role of β2 integrins is confirmed by the drastic phenotype of patients suffering from leukocyte adhesion deficiencies, most often resulting in severe recurrent infections and, at the same time, a predisposition for autoimmune diseases. So far, studies on the role of β2 integrins in vivo employed mice with a constitutive knockout of all β2 integrins or either family member, respectively, which complicated the differentiation between the direct and indirect effects of β2 integrin deficiency for distinct cell types. The recent generation and characterization of transgenic mice with a cell-type-specific knockdown of β2 integrins by our group has enabled the dissection of cell-specific roles of β2 integrins. Further, integrin receptors have been recognized as target receptors for the treatment of inflammatory diseases as well as tumor therapy. However, whereas both agonistic and antagonistic agents yielded beneficial effects in animal models, the success of clinical trials was limited in most cases and was associated with unwanted side effects. This unfavorable outcome is most probably related to the systemic effects of the used compounds on all leukocytes, thereby emphasizing the need to develop formulations that target distinct types of leukocytes to modulate β2 integrin activity for therapeutic applications.

Systemic lupus erythematosus Association between Osteomyelitis: A two-sample Mendelian randomization study in European population

Background

Systemic lupus erythematosus (SLE) has been correlated with osteomyelitis (OM), yet the underlying causal relationship remains poorly understood. This study aims to investigate the causal association between SLE and OM using Mendelian randomization (MR) analysis.

Methods

Genetic instrumental variables (IVs) correlated with SLE were extracted from a comprehensive genome-wide association study (GWAS) summary database (5201 cases and 9066 controls). OM was considered a SLE phenotype, and summary data from the fast GWA data portal were utilized for the analysis. Eligible IVs were extracted following rigorous quality control measures (P < 5 × 10-8, LD r2>0.001, distance 1 Mb, and F > 10). MR analysis was conducted using the Inverse Variance Weighted (IVW), MR-Egger, and Weighted Median (WM) methods after excluding potential confounders. Cochran's Q was applied for heterogeneity test. Pleiotropy was evaluated through MR-Egger intercept, MR-Pleiotropy Residual Sum and Outlier (MR-PRESSO) method, and Leave-one-SNP-out analysis.

Result

A total of 40 eligible IVs were included for MR analysis. IVW results demonstrated a positive causal association between SLE and OM (P = 0.049, OR = 1.167). Heterogeneity analysis reveal no significant heterogeneity in the IVW analysis (P = 0.5503). Pleiotropy tests, including MR-PRESSO global test and MR-Egger intercept, indicated no evidence of pleiotropy in our findings (P > 0.05). Additionally, the Leave-one-SNP-out analysis showed no substantial deviations when removing individual SNPs, thus supporting the robustness of our results.

Conclusion

This study establishes a genetic causal relationship between SLE and OM, indicating an increased risk of developing OM in individuals with SLE. Therefore, proactive management of SLE is advised to mitigate the risk of developing OM.

Identification and validation of immune-associated NETosis subtypes and biomarkers in anti-neutrophil cytoplasmic antibody associated glomerulonephritis

Background

NETosis is a new form of cell death, marked by DNA chromatin release from dead neutrophils. While it aids in microbe defense, it may worsen inflammation in autoimmune diseases, causing tissue harm. The impact of NETosis on Anti-neutrophil Cytoplasmic Antibody-associated Glomerulonephritis (ANCA-GN) remains unexplored and requires investigation.

Methods

First, a weighted gene co-expression network analysis (WGCNA) was conducted to uncover differential expression of neutrophil extranuclear trap-associated genes (DE-NETs) in ANCA-GN. The NETosisScore model was established through the single sample gene set enrichment analysis (ssGSEA), which categorized all patients into high-risk and low-risk groups. The accuracy of model was assessed by ROC curve. The biological function of various subgroups was explored through Gene Set Variation Analysis (GSVA), while the abundance of immune cell infiltration was measured with CIBERSORT. Furthermore, the key NETosis-related genes (NRGs) were identified using three machine learning algorithms, and their relationship with renal function was analyzed through the NephroseqV5 database. Through the application of qPCR and immunohistochemical staining techniques, the mRNA and protein expression levels of NRGs were determined in patients with ANCA-GN and control.

Results

A NETosisScore model was developed from 18 DE-NETs using the ssGSEA algorithm. The model's ability to predict ANCA-GN patients with a ROC AUC of 0.921. The high-risk group in ANCA-GN showed enrichment of immune-related pathways and greater infiltration of immune cells, as revealed by KEGG enrichment analysis and CIBERSORT. Using three machine learning algorithms, we identified six NRGs. Significant positive correlations were found between NRGs and CCR, macrophages, T-cell co-inhibition, and TIL. Further KEGG analysis revealed that the functions of NRGs may be closely related to the toll-like receptor signaling pathway. The levels of NRGs increased as kidney function declined and were positively correlated with Scr (serum creatinine) and negatively correlated with GFR (glomerular filtration rate), qPCR analysis showed increased expression of most NRGs in ANCA-GN patients. Furthermore, immunohistochemical staining confirmed higher expression of all NRGs in ANCA-GN patients.

Conclusion

NETosisScore model accurately predicts high-risk patients in ANCA-GN with enriched immune pathways, 6 NRGs identified as potential biomarkers.

Identification and validation of glomerulotubular crosstalk genes mediating IgA nephropathy by integrated bioinformatics

Background

IgA nephropathy (IgAN), which has been reported as the most prevalent glomerulonephritis globally, is the major contributor to end-stage renal diseases. This bioinformatics study aimed to explore glomerulotubular crosstalk genes and dysregulated pathways relating to the pathogenesis of IgAN.

Methods

The microarray datasets from the Gene Expression Omnibus (GEO) database were searched. Weighted gene co-expression network analysis (WGCNA) and differentially expressed genes (DEGs) of both glomeruli and tubulointerstitium were conducted individually. The co-expression gene modules of glomeruli and tubulointerstitium were compared via gene function enrichment analysis. Subsequently, the crosstalk co-expression network was constructed via the STRING database and key genes were mined from the crosstalk network. Finally, key genes were validated using another GEO dataset (GSE99340) containing RNA-seq data of IgAN and lupus nephritis, and their potential diagnostic values were shown using receiver operating characteristic (ROC) analysis.

Results

Five hundred eighty-three DEGs and eight modules were identified in glomerular samples, while 272 DEGs and four modules were in tubulointerstitial samples. There were 119 overlapping DEGs between the two groups. Among the distinctive modules, four modules in glomeruli and one module in tubulointerstitium were positively associated with IgAN. While four modules in glomeruli and two modules in tubulointerstitium were negatively associated with IgAN. The top ten key genes screened by CytoHubba were ITGAM, ALB, TYROBP, ITGB2, CYBB, HCK, CSF1R, LAPTM5, FN1, and CTSS. Compared with lupus nephritis, there were significant differences in the expression levels of CYBB, CTSS and TYROBP (P < 0.05), while other key genes showed no significant difference. Meanwhile, CYBB, CTSS, and TYROBP demonstrated possible diagnostic significance.

Conclusions

The crosstalk genes confirmed in this study may provide novel insight into the pathogenesis of IgAN. Immune-related pathways are associated with both glomerular and tubulointerstitial injuries in IgAN. The glomerulotubular crosstalk might perform a role in the pathogenesis of IgAN.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02779-7.

Identification of hub genes and transcription factors in patients with rheumatoid arthritis complicated with atherosclerosis

The aim of this study was to explore the overlapping key genes, pathway networks and transcription factors (TFs) related to the pathogenesis of rheumatoid arthritis (RA) and atherosclerosis. The gene expression profiles of RA and atherosclerosis were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between RA and atherosclerosis were identified. The biological roles of common DEGs were explored through enrichment analysis. Hub genes were identified using protein–protein interaction networks. TFs were predicted using Transcriptional Regulatory Relationships Unraveled by Sentence Based Text Mining (TRRUST) database. The hub genes and TFs were validated with other datasets. The networks between TFs and hub genes were constructed by CytoScape software. A total of 131 DEGs (all upregulated) were identified. Functional enrichment analyses indicated that DEGs were mostly enriched in leukocyte migration, neutrophil activation, and phagocytosis. CytoScape demonstrated 12 hub genes and one gene cluster module. Four of the 12 hub genes (CSF1R, CD86, PTPRC, and CD53) were validated by other datasets. TRRUST predicted two TFs, including Spi-1 proto-oncogene (SPI1) and RUNX family transcription factor 1(RUNX1). The expression of RUNX1 was validated with another dataset. Our study explored the common pathogenesis of RA and atherosclerosis. These results may guide future experimental research and clinical transformation.

Integrin Regulated Autoimmune Disorders: Understanding the Role of Mechanical Force in Autoimmunity

The pathophysiology of autoimmune disorders is multifactorial, where immune cell migration, adhesion, and lymphocyte activation play crucial roles in its progression. These immune processes are majorly regulated by adhesion molecules at cell–extracellular matrix (ECM) and cell–cell junctions. Integrin, a transmembrane focal adhesion protein, plays an indispensable role in these immune cell mechanisms. Notably, integrin is regulated by mechanical force and exhibit bidirectional force transmission from both the ECM and cytosol, regulating the immune processes. Recently, integrin mechanosensitivity has been reported in different immune cell processes; however, the underlying mechanics of these integrin-mediated mechanical processes in autoimmunity still remains elusive. In this review, we have discussed how integrin-mediated mechanotransduction could be a linchpin factor in the causation and progression of autoimmune disorders. We have provided an insight into how tissue stiffness exhibits a positive correlation with the autoimmune diseases’ prevalence. This provides a plausible connection between mechanical load and autoimmunity. Overall, gaining insight into the role of mechanical force in diverse immune cell processes and their dysregulation during autoimmune disorders will open a new horizon to understand this physiological anomaly.

Identification of blood-derived candidate gene markers and a new 7-gene diagnostic model for multiple sclerosis

Background

Multiple sclerosis (MS) is a central nervous system disease with a high disability rate. Modern molecular biology techniques have identified a number of key genes and diagnostic markers to MS, but the etiology and pathogenesis of MS remain unknown.

Results

In this study, the integration of three peripheral blood mononuclear cell (PBMC) microarray datasets and one peripheral blood T cells microarray dataset allowed comprehensive network and pathway analyses of the biological functions of MS-related genes. Differential expression analysis identified 78 significantly aberrantly expressed genes in MS, and further functional enrichment analysis showed that these genes were associated with innate immune response-activating signal transduction (p = 0.0017), neutrophil mediated immunity (p = 0.002), positive regulation of innate immune response (p = 0.004), IL-17 signaling pathway (p < 0.035) and other immune-related signaling pathways. In addition, a network of MS-specific protein–protein interactions (PPI) was constructed based on differential genes. Subsequent analysis of network topology properties identified the up-regulated CXCR4, ITGAM, ACTB, RHOA, RPS27A, UBA52, and RPL8 genes as the hub genes of the network, and they were also potential biomarkers of MS through Rap1 signaling pathway or leukocyte transendothelial migration. RT-qPCR results demonstrated that CXCR4 was obviously up-regulated, while ACTB, RHOA, and ITGAM were down-regulated in MS patient PBMC in comparison with normal samples. Finally, support vector machine was employed to establish a diagnostic model of MS with a high prediction performance in internal and external datasets (mean AUC = 0.97) and in different chip platform datasets (AUC = (0.93).

Conclusion

This study provides new understanding for the etiology/pathogenesis of MS, facilitating an early identification and prediction of MS.

Clinical features and expression of type I interferon-inducible genes in systemic lupus erythematosus patients harboring rs1143679 polymorphism in China: a single-center, retrospective study

OBJECTIVE

This case-control study aimed to analyze the clinical features and determine the expression of type I interferon-induced genes in systemic lupus erythematosus (SLE) patients harboring the CD11b rs1143679 single-nucleotide polymorphism (SNP) and elucidate whether it is involved in the relapses of SLE.

METHODS

One hundred twenty-five relatively inactive SLE patients with SLEDAI scores < 6, including 102 CD11b rs1143679 G allele patients as controls and 23 rs1143679 A allele carriers as cases, were enrolled from the SLE patient specimen bank in the Department of Rheumatology and Immunology. The sample set was retrospectively analyzed for differences in clinical features, and quantitative PCR and Western blot analyses were performed to evaluate the relative expression of type I interferon (IFN)-inducible genes.

RESULTS

The 24-h urinary protein levels in the case group were significantly elevated, and serum C3 levels were significantly reduced compared with those in the control group (P = 0.019 and P = 0.021, respectively). The relative mRNA levels of IFN-inducible genes IFIT1, IFIT4, and ISG15 in the case group were higher than that in the control group (P = 0.0257, 0.0344, and 0.0311, respectively) and matched with the Western blot results.

CONCLUSIONS

The relative expression of type I IFN-inducible genes in inactive SLE patients harboring the CD11b rs1143679 polymorphism was higher than that in other lupus patients. These findings suggest that the rs1143679 SNP can precipitate relapses in inactive SLE patients.

KEY POINTS

• The rs1143679 GA genotype was associated with SLE clinical features. • The rs1143679 GA genotype showed higher interferon-inducible gene expression relative to the GG genotype.

ITGAM is a risk factor to systemic lupus erythematosus and possibly a protection factor to rheumatoid arthritis in patients from Mexico

Introduction

ITGAM has consistently been associated with susceptibility to systemic lupus erythematosus (SLE) in many ethnically diverse populations. However, in populations with higher Amerindian ancestry (like Yucatan) or highly admixed population (like Mexican), ITGAM has seldom been evaluated (except few studies where patients with childhood-onset SLE were included). In addition, ITGAM has seldom been evaluated in patients with rheumatoid arthritis (RA). Here, we evaluated whether four single nucleotide polymorphisms (SNPs), located within ITGAM, were associated with SLE and RA susceptibility in patients from Mexico.

Methods

Our study consisted of 1,462 individuals, which included 363 patients with SLE (292 from Central Mexico and 71 from Yucatan), and 621 healthy controls (504 from Central Mexico and 117 from Yucatan). Our study also included 478 patients with RA from Central Mexico. TaqMan assays were used to obtain the genotypes of the four SNPs: rs34572943 (G/A), rs1143679 (G/A), rs9888739 (C/T), and rs1143683 (C/T). We also verified the genotypes by Sanger sequencing. Fisher's exact test and permutation test were employed to evaluate the distribution of genotype, allele, and haplotype between patients and controls.

Results

Our data show that all four ITGAM SNPs are significantly associated with susceptibility to SLE using both genotypic and allelic association tests (corrected for multiple testing, but not for population stratification). A second study carried out in patients from Yucatan, a southeastern part of Mexico (with a high Amerindian ancestry), also replicated SLE association with all four SNPs, including the functional SNP, rs1143679 (OR = 24.6 and p = 9.3X10^-6). On the other hand, none of the four SNPs are significant in RA after multiple testing. Interestingly, the GACC haplotype, which carries the ITGAM rs1143679 (A) minor allele, showed an association with protection against RA (OR = 0.14 and p = 3.0x10^-4).

Conclusion

Our data displayed that ITGAM is a risk factor to SLE in individuals of Mexican population. Concurrently, a risk haplotype in ITGAM confers protection against RA.

Mice expressing the variant rs1143679 allele of ITGAM (CD11b) show impaired DC-mediated T cell proliferation

Genome-wide association studies (GWAS) and functional genomic analyses have implicated several ITGAM (CD11b) single-nucleotide polymorphisms (SNPs) in the development of SLE and other disorders. ITGAM encodes the αM chain of the β2 integrin Mac-1, a receptor that plays important roles in myeloid cell functions. The ITGAM SNP rs1143679, which results in an arginine to histidine change at amino acid position 77 of the CD11b protein, has been shown to reduce binding to several ligands and to alter Mac-1-mediated cellular response in vitro. Importantly, however, the potential contribution of this SNP variant to the initiation and/or progression of immune and inflammatory processes in vivo remains unexplored. Herein, we describe for the first time the generation and characterization of a mouse line expressing the 77His variant of CD11b. Surprisingly, we found that 77His did not significantly affect Mac-1-mediated leukocyte migration and activation as assessed using thioglycollate-induced peritonitis and LPS/TNF-α-induced dermal inflammation models. In contrast, expression of this variant did alter T cell immunity, as evidenced by significantly reduced proliferation of ovalbumin (OVA)-specific transgenic T cells in 77His mice immunized with OVA. Reduced antigen-specific T cell proliferation was also observed when either 77His splenic dendritic cells (DCs) or bone marrow-derived DCs were used as antigen-presenting cells (APCs). Although more work is necessary to determine how this alteration might influence the development of SLE or other diseases, these in vivo findings suggest that the 77His variant of CD11b can compromise the ability of DCs to induce antigen-driven T cell proliferation.

Association of ITGAX and ITGAM gene polymorphisms with susceptibility to IgA nephropathy

Previous genome-wide association studies have discovered significant association at ITGAX-ITGAM on 16p11.2 for IgA nephropathy (IgAN). In this study, we performed a two-stage association study that enrolled 1700 IgAN cases and 2400 controls to further investigate the relationship of ITGAX and ITGAM gene polymorphisms with IgAN. Seven single-nucleotide polymorphisms (SNPs) were selected for genotyping in 1000 IgAN cases and 1000 healthy controls in the discovery stage, and the significant SNP was further validated in additional 700 IgAN cases and 1400 healthy controls. We found that four SNPs (rs11150619, rs11150614, rs7190997, and rs4597342) showed potential associations with IgAN susceptibility in the discovery stage, but only SNP rs11150619 was further genotyped in the validation stage after multiple testing. The results indicated that rs11150619 was significantly associated with IgAN in the combined samples (OR = 0.81, 95%CI = 0.71-0.91, and dominant P = 6.68 × 10^-4). Moreover, patients with TT genotype of rs11150619 exhibited increased estimated glomerular filtration rate levels and a reduced proportion of global sclerosis compared with those with TC and CC genotypes. Our results suggested that ITGAX and ITGAM gene polymorphisms were associated with IgAN in a Chinese Han population, and the rs11150619-T allele showed a potential protective role for IgAN.

Autoimmune Thyroid Disease in Patients with Systemic Lupus Erythematosus: A 7-year Retrospective Study in China

BACKGROUND

The study was a retrospective case-controlled study. We aimed to determine the clinical and laboratory features of systemic lupus erythematosus (SLE) and compared the features of autoimmune thyroid disease (AITD) with those of SLE.

MATERIALS AND METHODS

The study included 38 patients with SLE with AITD (SLE-AITD) and 190 age- and gender-matched SLE patients. The distribution of sociodemographic and clinical factors was compared between the SLE-AITD and SLE groups using Chi-square tests for gender and t tests for others. Univariate and multivariate logistic regression models were used to identify factors associated with the prevalence of AITD among SLE patients.

RESULTS

In univariate analysis, malar rash, oral ulcers, serositis, anti-double-stranded DNA antibody positivity (anti-dsDNA+), anti-Sjögren's syndrome type A antibodies (SSA), anti-Sjögren's syndrome type B antibodies (SSB), low complement 3 (C3), and low complement 4 (C4) were significantly different between the SLE-AITD and SLE groups. There were no significant differences among other clinical or laboratory features. In multivariate analysis, serositis (adjusted odds ratio [AOR], 3.64; P = 0.00), anti-dsDNA+ (AOR, 0.30; P = 0.01) and low C3 (AOR, 0.30; P = 0.02) were all associated with SLE-AITD.

CONCLUSIONS

In our study, serositis was a risk factor for AITD, so we propose that AITD should be considered in lupus patients with serositis.

Celiac Disease Autoimmunity

Celiac disease is an autoimmune condition triggered by the ingestion of gluten, the protein fraction of wheat, barley and rye. It is not simply an intestinal disease; it is multifactorial caused by many different genetic factors acting together with non-genetic causes. Similar to other autoimmune diseases, celiac disease is a polygenic disorder for which the major histocompatibility complex locus is the most important genetic factor, and is the result of an immune response to self-antigens leading to tissue destruction and the autoantibodies production. Celiac disease exemplifies how an illness can have autoimmune-like features having to be driven by exogenous antigen and how can be reasonably considered as a model of organ-specific autoimmunity.

A Novel Association of Polymorphism in the ITGA4 Gene Encoding the VLA-4 α4 Subunit with Increased Risk of Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent cause of dementia in elderly people worldwide. Many studies support the hypothesis that the inflammation of the CNS contributes to the neurodegeneration and disease progression. The integrin molecule α4β1, also known as very late antigen 4 (VLA-4), belongs to adhesion molecules that activate the inflammatory process through the migration of immune cells into the CNS. Therefore, the objective of our study was to analyze the association between two polymorphisms located in the ITGA4 gene encoding the α4 subunit of VLA-4 and the risk of AD. 104 late-onset AD patients and 206 control subjects from Slovakia were genotyped for ITGA4 gene SNP polymorphism rs113276800 (-269C/A) and rs1143676 (+3061A/G). The same study cohorts were also genotyped for the APOE-ε4, which is a known genetic factor associated with increased risk of AD developing. ITGA4 polymorphism analysis revealed significantly higher frequency of the +3061AG carriers in AD group compared to the controls (P ≤ 0.05). Following the APOE-ε4 stratification of study groups, the association remained significant only in APOE-ε4 noncarriers. Our study suggests a novel association of ITGA4 +3061A/G polymorphism with AD and its possible contribution to the disease pathology.

Genetics of human lupus nephritis

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease characterized by immune complex formation with multi-organ manifestations. Lupus nephritis (LN) is one of the most severe types of organ damage in SLE, and it clearly contributes to increased morbidity and mortality due to SLE. LN occurs more frequently and is more severe in non-European ancestral backgrounds, although the cause of this disparity remains largely unknown. Genetic factors play an important role in the pathogenesis of SLE. Although many SLE susceptibility genes have been identified, the genetic basis of LN is not as well understood. While some of the established general SLE susceptibility genes are associated with LN, recent discoveries highlight a number of genes with renal functions that are specifically associated with LN. Some of these genes associated with LN help to explain the disparity in the prevalence of nephritis between individuals with SLE, and also partially explain differences in LN between ancestral backgrounds. Moreover, not only the gene mutations, but also post-translational modifications seem to play important roles in the pathogenesis of LN. Overall it seems likely that a combination of general SLE susceptibility genes cooperate with LN specific risk genes to result in the genetic propensity for LN. In this review, we will outline the genetic contribution to LN and describe possible roles of LN susceptibility genes.

The many faces of Mac-1 in autoimmune disease

Mac-1 (CD11b/CD18) is a β2 integrin classically regarded as a pro-inflammatory molecule because of its ability to promote phagocyte cytotoxic functions and enhance the function of several effector molecules such as FcγR, uPAR, and CD14. Nevertheless, recent reports have revealed that Mac-1 also plays significant immunoregulatory roles, and genetic variants in ITGAM, the gene that encodes CD11b, confer risk for the autoimmune disease systemic lupus erythematosus (SLE). This has renewed interest in the physiological roles of this integrin and raised new questions on how its seemingly opposing biological functions may be regulated. Here, we provide an overview of the CD18 integrins and how their activation may be regulated as this may shed light on how the opposing roles of Mac-1 may be elicited. We then discuss studies that exemplify Mac-1's pro-inflammatory versus regulatory roles particularly in the context of IgG immune complex-mediated inflammation. This includes a detailed examination of molecular mechanisms that could explain the risk-conferring effect of rs1143679, a single nucleotide non-synonymous Mac-1 polymorphism associated with SLE.

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.

The genetics of human autoimmune disease: A perspective on progress in the field and future directions

Progress in defining the genetics of autoimmune disease has been dramatically enhanced by large scale genetic studies. Genome-wide approaches, examining hundreds or for some diseases thousands of cases and controls, have been implemented using high throughput genotyping and appropriate algorithms to provide a wealth of data over the last decade. These studies have identified hundreds of non-HLA loci as well as further defining HLA variations that predispose to different autoimmune diseases. These studies to identify genetic risk loci are also complemented by progress in gene expression studies including definition of expression quantitative trait loci (eQTL), various alterations in chromatin structure including histone marks, DNase I sensitivity, repressed chromatin regions as well as transcript factor binding sites. Integration of this information can partially explain why particular variations can alter proclivity to autoimmune phenotypes. Despite our incomplete knowledge base with only partial definition of hereditary factors and possible functional connections, this progress has and will continue to facilitate a better understanding of critical pathways and critical changes in immunoregulation. Advances in defining and understanding functional variants potentially can lead to both novel therapeutics and personalized medicine in which therapeutic approaches are chosen based on particular molecular phenotypes and genomic alterations.

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.

Rare variants at 16p11.2 are associated with common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is characterized clinically by inadequate quantity and quality of serum immunoglobulins with increased susceptibility to infections, resulting in significant morbidity and mortality. Only a few genes have been uncovered, and the genetic background of CVID remains elusive to date for the majority of patients.

OBJECTIVE

We sought to seek novel associations of genes and genetic variants with CVID.

METHODS

We performed association analyses in a discovery cohort of 164 patients with CVID and 19,542 healthy control subjects genotyped on the Immuno BeadChip from Illumina platform; replication of findings was examined in an independent cohort of 135 patients with CVID and 2,066 healthy control subjects, followed by meta-analysis.

RESULTS

We identified 11 single nucleotide polymorphisms (SNPs) at the 16p11.2 locus associated with CVID at a genome-wide significant level in the discovery cohort. The most significant SNP, rs929867 (P = 6.21 × 10(-9)), is in the gene fused-in-sarcoma (FUS), with 4 other SNPs mapping to integrin CD11b (ITGAM). Results were confirmed in our replication cohort. Conditional association analysis suggests a single association signal at the 16p11.2 locus. A strong trend of association was also seen for 38 SNPs (P < 5 × 10(-5)) in the MHC region, supporting that this is a genuine CVID locus. Interestingly, we found that 80% of patients with the rare ITGAM variants have reduced switched memory B-cell counts.

CONCLUSION

We report a novel association of CVID with rare variants at the FUS/ITGAM (CD11b) locus on 16p11.2. The association signal is enriched for promoter/enhancer markers in the ITGAM gene. ITGAM encodes the integrin CD11b, a part of complement receptor 3, a novel candidate gene implicated here for the first time in the pathogenesis of CVID.

VLA4 Gene Polymorphism and Susceptibility to Multiple Sclerosis in Slovaks

Multiple sclerosis (MS) is an inflammatory autoimmune disease occurring in genetically sensitive individuals. As migration of immune cells into the CNS is facilitated by the Very Late Antigen 4 (VLA-4) integrin molecule, the VLA4 gene may be considered as a plausible candidate genetic risk factor for susceptibility to MS. Therefore, the objective of our study was to investigate the association between two genetic polymorphisms located in the VLA4 gene and the risk of multiple sclerosis. One hundred seventeen MS patients and 165 control subjects from Slovakia were genotyped for VLA4 gene SNP polymorphisms at positions 269 (C/A) and 3061 (A/G). The same study cohorts were also genotyped for the rs3135388 polymorphism tagging the HLA-DRB1*15:01 allele, which is a known genetic factor associated with susceptibility to develop MS in many populations. Our findings show for the first time that the rs3135388 polymorphism is a strong risk factor for MS in the Slovak population. Investigation of the VLA4 gene polymorphisms revealed a significantly higher frequency of the 3061AG genotype in MS patients compared to the controls (P ≤ 0.05). We suggest that the 3061AG polymorphic variant is an independent genetic risk factor for MS development in our population as it was significantly associated with this disease. The association was also confirmed after applying multivariate logistic-regression analysis adjusted for gender, age and HLA-DRB1*15:01 positivity as possible influencing factors.

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.

Association between the functional ITGAM rs1143679 G/A polymorphism and systemic lupus erythematosus/lupus nephritis or rheumatoid arthritis: an update meta-analysis

The aim of this study was to determine whether the functional integrin-α-M (ITGAM) rs1143679 polymorphism is associated with susceptibility to systemic lupus erythematosus (SLE), lupus nephritis (LN), and rheumatoid arthritis (RA). A series of meta-analyses were conducted to test for associations between the ITGAM rs1143679 polymorphism and SLE, LN, or RA. A total of 24 comparisons involving 7,738 patients and 8,309 controls for SLE, and 2,663 patients and 2,694 controls in RA were considered. Meta-analysis showed a significant association between the ITGAM rs1143679 A allele and SLE in all subjects (OR 1.773, 95 % CI 1.656, 1.901, p < 1.0 × 10(-9)). After stratification by ethnicity, the A allele was found to be significantly associated with SLE in European, Latin American, and Asian. A significant association was also found between the ITGAM A allele and lupus nephritis in Europeans (OR 2.131, 95 % CI 1.565, 2.903, p = 1.6 × 10(-7)). However, no association was found between RA and the ITGAM rs1143679 polymorphism. Our meta-analyses confirm that the ITGAM rs1143679 polymorphism is associated with SLE susceptibility in different ethnic groups and demonstrate that the polymorphism is associated with LN in European.

Celiac disease as an autoimmune condition

Autoimmune diseases have become a major medical problem of recent years. Celiac disease is an autoimmune disease model. The aim of our study was to follow the changes in the clinical autoimmunity picture of the celiac disease from recent years. The study of autoimmunity in celiac disease has focused on associated diseases with the aforementioned disease: type 1 diabetes mellitus, thyroid autoimmunity disease, Graves’ disease, Hashimoto's disease, systemic lupus erythematosus, systemic sclerosis, spondyloarthritis, hyperprolactinemia, Turner syndrome, Addison's disease, sensory neuronopathies. Immune reactivity to tissue transglutaminase targeted autoantibodies and other autoantigens, including transglutaminase 3, actin, ganglioside, collagen, calreticulin or zonulin which have been reported in the celiac disease. New research directions given by celiac disease autoimmunity, interleukin 1, interleukin 2, protein tyrosine phosphatase non-receptor type 22, CD4+CD25+ T lymphocytes, cytotoxic T-lymphocyte antigen 4, infection with Necator americanus and definitive identification of pathogenic T cell epitopes, seem to provide a solution in celiac disease treatment.

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.

Combined protein- and nucleic acid-level effects of rs1143679 (R77H), a lupus-predisposing variant within ITGAM

Integrin alpha M (ITGAM; CD11b) is a component of the macrophage-1 antigen complex, which mediates leukocyte adhesion, migration and phagocytosis as part of the immune system. We previously identified a missense polymorphism, rs1143679 (R77H), strongly associated with systemic lupus erythematosus (SLE). However, the molecular mechanisms of this variant are incompletely understood. A meta-analysis of published and novel data on 28 439 individuals with European, African, Hispanic and Asian ancestries reinforces genetic association between rs1143679 and SLE [Pmeta = 3.60 × 10(-90), odds ratio (OR) = 1.76]. Since rs1143679 is in the most active region of chromatin regulation and transcription factor binding in ITGAM, we quantitated ITGAM RNA and surface protein levels in monocytes from patients with each rs1143679 genotype. We observed that transcript levels significantly decreased for the risk allele ('A') relative to the non-risk allele ('G'), in a dose-dependent fashion: ('AA' < 'AG' < 'GG'). CD11b protein levels in patients' monocytes were directly correlated with RNA levels. Strikingly, heterozygous individuals express much lower (average 10- to 15-fold reduction) amounts of the 'A' transcript than 'G' transcript. We found that the non-risk sequence surrounding rs1143679 exhibits transcriptional enhancer activity in vivo and binds to Ku70/80, NFKB1 and EBF1 in vitro, functions that are significantly reduced with the risk allele. Mutant CD11b protein shows significantly reduced binding to fibrinogen and vitronectin, relative to non-risk, both in purified protein and in cellular models. This two-pronged contribution (nucleic acid- and protein-level) of the rs1143679 risk allele to decreasing ITGAM activity provides insight into the molecular mechanisms of its potent association with SLE.

Autoimmunity in 2012

The initiation and perpetuation of autoimmunity recognize numerous checkpoints, from the genomic susceptibility to the breakdown of tolerance. This latter phenomenon includes the loss of B cell anergy and T regulatory cell failure, as well as the production of autoantibodies and autoreactive T cells. These mechanisms ultimately lead to tissue injury via different mechanisms that span from the production of proinflammatory cytokines to the chemotaxis of immune cells to the target sites. The pathways to autoimmunity have been widely investigated over the past year and resulted in a number of articles in peer-reviewed journals that has increased by nearly 10 % compared to 2011. We herein follow on the attempt to provide a brief discussion of the majority of articles on autoimmune diseases that were published in the major immunology journals in the previous solar year. The selection is necessarily arbitrary and may thus not be seen as comprehensive but reflects current research trends. Indeed, 2012 articles were mostly dedicated to define new and old mechanisms with potential therapeutic implications in autoimmunity in general, though based on specific clinical conditions or animal models. As paradigmatic examples, the environmental influence on autoimmunity, Th17 changes modulating the autoimmune response, serum autoantibodies and B cell changes as biomarkers and therapeutic targets were major issues addressed by experimental articles in 2012. Further, a growing number of studies investigated the sex bias of autoimmunity and supported different working hypotheses to explain the female predominance, including sex chromosome changes and reproductive life factors. In conclusion, the resulting scenario illustrates that common factors may underlie different autoimmune diseases and this is well represented by the observed alterations in interferon-α and TGFβ or by the shared signaling pathways.

Gender and autoimmune comorbidity in multiple sclerosis

BACKGROUND

The female preponderance in incidence of multiple sclerosis (MS) calls for investigations into sex differences in comorbidity with other autoimmune diseases (ADs).

OBJECTIVES

To determine whether male and female patients with MS have a higher frequency of autoimmune comorbidity than controls, and to describe the type and frequency of ADs that are associated with MS.

METHODS

Our database was established by linkage of the Danish MS Registry to The Danish National Patient Register and consisted of 1403 patients of both sexes with clinical onset of MS between 2000 and 2004, and 25 matched controls for every case.

RESULTS

None of the ADs occurred more frequently in female cases than in controls. Male cases were more likely to have Type I diabetes mellitus (odds ratio (OR) = 3.34; 95% CI 1.40 - 7.02; p < 0.008), Crohn's disease (OR = 5.03; 95% CI 1.18 - 16.10; p = 0.03) and systemic lupus erythematosus (OR = 12.55; 95% CI 1.62 - 69.95; p = 0.02) than male controls.

CONCLUSIONS

Autoimmune disorders are rare, but some of them tend to occur together with MS at a higher rate than in controls. Although women are generally more prone to ADs than men, significantly increased occurrence of other ADs were only found in male MS patients.

The CD11b-integrin (ITGAM) and systemic lupus erythematosus

Variations at the ITGAM gene, which encodes for the CD11b chain of the Mac-1 (alphaMbeta2; CD11b/CD18; complement receptor-3) integrin, is one of the strongest genetic risk factors for systemic lupus erythematosus (SLE). More specifically, a genetic variant (rs1143679) which results in an arginine to histidine substitution at position 77 in the extracellular portion of the integrin is associated with disease. It has recently been shown that this amino acid substitution results in a dysfunctional integrin, which is deficient in mediating cell adhesion to integrin ligands, phagocytosis and in addition cannot restrict inflammatory cytokine production in macrophages. In this review, we discuss immunological functions of the Mac-1 integrin and how defects in the genetic variant of Mac-1 may relate to SLE development.

Celiac disease and autoimmune-associated conditions

Celiac disease (CD) is frequently accompanied by a variety of extradigestive manifestations, thus making it a systemic disease rather than a disease limited to the gastrointestinal tract. This is primarily explained by the fact that CD belongs to the group of autoimmune diseases. The only one with a known etiology is related to a permanent intolerance to gluten. Remarkable breakthroughs have been achieved in the last decades, due to a greater interest in the diagnosis of atypical and asymptomatic patients, which are more frequent in adults. The known presence of several associated diseases provides guidance in the search of oligosymptomatic cases as well as studies performed in relatives of patients with CD. The causes for the onset and manifestation of associated diseases are diverse; some share a similar genetic base, like type 1 diabetes mellitus (T1D); others share pathogenic mechanisms, and yet, others are of unknown nature. General practitioners and other specialists must remember that CD may debut with extraintestinal manifestations, and associated illnesses may appear both at the time of diagnosis and throughout the evolution of the disease. The implementation of a gluten-free diet (GFD) improves the overall clinical course and influences the evolution of the associated diseases. In some cases, such as iron deficiency anemia, the GFD contributes to its disappearance. In other disorders, like T1D, this allows a better control of the disease. In several other complications and/or associated diseases, an adequate adherence to a GFD may slow down their evolution, especially if implemented during an early stage.

Phagocytosis is the main CR3-mediated function affected by the lupus-associated variant of CD11b in human myeloid cells

The CD11b/CD18 integrin (complement receptor 3, CR3) is a surface receptor on monocytes, neutrophils, macrophages and dendritic cells that plays a crucial role in several immunological processes including leukocyte extravasation and phagocytosis. The minor allele of a non-synonymous CR3 polymorphism (rs1143679, conversation of arginine to histidine at position 77: R77H) represents one of the strongest genetic risk factor in human systemic lupus erythematosus, with heterozygosity (77R/H) being the most common disease associated genotype. Homozygosity for the 77H allele has been reported to reduce adhesion and phagocytosis in human monocytes and monocyte-derived macrophages, respectively, without affecting surface expression of CD11b. Herein we comprehensively assessed the influence of R77H on different CR3-mediated activities in monocytes, neutrophils, macrophages and dendritic cells. R77H did not alter surface expression of CD11b including its active form in any of these cell types. Using two different iC3b-coated targets we found that the uptake by heterozygous 77R/H macrophages, monocytes and neutrophils was significantly reduced compared to 77R/R cells. Allele-specific transduced immortalized macrophage cell lines demonstrated that the minor allele, 77H, was responsible for the impaired phagocytosis. R77H did not affect neutrophil adhesion, neutrophil transmigration in vivo or Toll-like receptor 7/8-mediated cytokine release by monocytes or dendritic cells with or without CR3 pre-engagement by iC3b-coated targets. Our findings demonstrate that the reduction in CR3-mediated phagocytosis associated with the 77H CD11b variant is not macrophage-restricted but demonstrable in other CR3-expressing professional phagocytic cells. The association between 77H and susceptibility to systemic lupus erythematosus most likely relates to impaired waste disposal, a key component of lupus pathogenesis.

The rs1143679 (R77H) lupus associated variant of ITGAM (CD11b) impairs complement receptor 3 mediated functions in human monocytes

OBJECTIVES

The rs1143679 variant of ITGAM, encoding the R77H variant of CD11b (part of complement receptor 3; CR3), is among the strongest genetic susceptibility effects in human systemic lupus erythematosus (SLE). The authors aimed to demonstrate R77H function in ex-vivo human cells.

METHODS

Monocytes/monocyte-derived macrophages from healthy volunteers homozygous for either wild type (WT) or 77H CD11b were studied. The genotype-specific expression of CD11b, and CD11b activation using conformation-specific antibodies were measured. Genotype-specific differences in iC3b-mediated phagocytosis, adhesion to a range of ligands and the secretion of cytokines following CR3 ligation were studied. The functionality of R77H was confirmed by replicating findings in COS7 cells expressing variant-specific CD11b.

RESULTS

No genotype-specific difference in CD11b expression or in the expression of CD11b activation epitopes was observed. A 31% reduction was observed in the phagocytosis of iC3b opsonised sheep erythrocytes (sRBC(iC3b)) by 77H cells (p=0.003) and reduced adhesion to a range of ligands: notably a 24% reduction in adhesion to iC3b (p=0.014). In transfected COS7 cells, a 42% reduction was observed in phagocytosis by CD11b (77H)-expressing cells (p=0.004). A significant inhibition was seen in the release of Toll-like receptor 7/8-induced pro-inflammatory cytokines from WT monocytes when CR3 was pre-engaged using sRBC(iC3b), but no inhibition in 77H monocytes resulting in a significant difference between genotypes (interleukin (IL)-1β p=0.030; IL-6 p=0.029; tumour necrosis factor alpha p=0.027).

CONCLUSIONS

The R77H variant impairs a broad range of CR3 effector functions in human monocytes. This study discusses how perturbation of this pathway may predispose to SLE.

Variation in the ICAM1-ICAM4-ICAM5 locus is associated with systemic lupus erythematosus susceptibility in multiple ancestries

OBJECTIVE

Systemic lupus erythematosus (SLE; OMIM 152700) is a chronic autoimmune disease for which the aetiology includes genetic and environmental factors. ITGAM, integrin α(M) (complement component 3 receptor 3 subunit) encoding a ligand for intracellular adhesion molecule (ICAM) proteins, is an established SLE susceptibility locus. This study aimed to evaluate the independent and joint effects of genetic variations in the genes that encode ITGAM and ICAM.

METHODS

The authors examined several markers in the ICAM1-ICAM4-ICAM5 locus on chromosome 19p13 and the single ITGAM polymorphism (rs1143679) using a large-scale case-control study of 17 481 unrelated participants from four ancestry populations. The single-marker association and gene-gene interaction were analysed for each ancestry, and a meta-analysis across the four ancestries was performed.

RESULTS

The A-allele of ICAM1-ICAM4-ICAM5 rs3093030, associated with elevated plasma levels of soluble ICAM1, and the A-allele of ITGAM rs1143679 showed the strongest association with increased SLE susceptibility in each of the ancestry populations and the trans-ancestry meta-analysis (OR(meta)=1.16, 95% CI 1.11 to 1.22; p=4.88×10(-10) and OR(meta)=1.67, 95% CI 1.55 to 1.79; p=3.32×10(-46), respectively). The effect of the ICAM single-nucleotide polymorphisms (SNPs) was independent of the effect of the ITGAM SNP rs1143679, and carriers of both ICAM rs3093030-AA and ITGAM rs1143679-AA had an OR of 4.08 compared with those with no risk allele in either SNP (95% CI 2.09 to 7.98; p=3.91×10(-5)).

CONCLUSION

These findings are the first to suggest that an ICAM-integrin-mediated pathway contributes to susceptibility to SLE.

The genetics of lupus: a functional perspective

Systemic lupus erythematosus (SLE) is an autoimmune disease with a strong genetic component and is characterized by chronic inflammation and the production of anti-nuclear auto-antibodies. In the era of genome-wide association studies (GWASs), elucidating the genetic factors present in SLE has been a very successful endeavor; 28 confirmed disease susceptibility loci have been mapped. In this review, we summarize the current understanding of the genetics of lupus and focus on the strongest associated risk loci found to date (P <1.0 × 10−8). Although these loci account for less than 10% of the genetic heritability and therefore do not account for the bulk of the disease heritability, they do implicate important pathways, which contribute to SLE pathogenesis. Consequently, the main focus of the review is to outline the genetic variants in the known associated loci and then to explore the potential functional consequences of the associated variants. We also highlight the genetic overlap of these loci with other autoimmune diseases, which indicates common pathogenic mechanisms. The importance of developing functional assays will be discussed and each of them will be instrumental in furthering our understanding of these associated variants and loci. Finally, we indicate that performing a larger SLE GWAS and applying a more targeted set of methods, such as the ImmunoChip and next generation sequencing methodology, are important for identifying additional loci and enhancing our understanding of the pathogenesis of SLE.

Shared HLA Class II in Six Autoimmune Diseases in Latin America: A Meta-Analysis

The prevalence and genetic susceptibility of autoimmune diseases (ADs) may vary depending on latitudinal gradient and ethnicity. The aims of this study were to identify common human leukocyte antigen (HLA) class II alleles that contribute to susceptibility to six ADs in Latin Americans through a meta-analysis and to review additional clinical, immunological, and genetic characteristics of those ADs sharing HLA alleles. DRB1(∗)03:01 (OR: 4.04; 95%CI: 1.41-11.53) was found to be a risk factor for systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and type 1 diabetes mellitus (T1D). DRB1(∗)04:05 (OR: 4.64; 95%CI: 2.14-10.05) influences autoimmune hepatitis (AIH), rheumatoid arthritis (RA), and T1D; DRB1(∗)04:01 (OR: 3.86; 95%CI: 2.32-6.42) is a susceptibility factor for RA and T1D. Opposite associations were found between multiple sclerosis (MS) and T1D. DQB1(∗)06:02 and DRB1(∗)15 alleles were risk factors for MS but protective factors for T1D. Likewise, DQB1(∗)06:03 allele was a risk factor for AIH but a protective one for T1D. Several common autoantibodies and clinical associations as well as additional shared genes have been reported in these ADs, which are reviewed herein. These results indicate that in Latin Americans ADs share major loci and immune characteristics.

Introducing polyautoimmunity: secondary autoimmune diseases no longer exist

Similar pathophysiological mechanisms within autoimmune diseases have stimulated searches for common genetic roots. Polyautoimmunity is defined as the presence of more than one autoimmune disease in a single patient. When three or more autoimmune diseases coexist, this condition is called multiple autoimmune syndrome (MAS). We analyzed the presence of polyautoimmunity in 1,083 patients belonging to four autoimmune disease cohorts. Polyautoimmunity was observed in 373 patients (34.4%). Autoimmune thyroid disease (AITD) and Sjögren's syndrome (SS) were the most frequent diseases encountered. Factors significantly associated with polyautoimmunity were female gender and familial autoimmunity. Through a systematic literature review, an updated search was done for all MAS cases (January 2006-September 2011). There were 142 articles retrieved corresponding to 226 cases. Next, we performed a clustering analysis in which AITD followed by systemic lupus erythematosus and SS were the most hierarchical diseases encountered. Our results indicate that coexistence of autoimmune diseases is not uncommon and follows a grouping pattern. Polyautoimmunity is the term proposed for this association of disorders, which encompasses the concept of a common origin for these diseases.

Unraveling the genetic component of systemic sclerosis

Systemic sclerosis (SSc) is a severe connective tissue disorder characterized by extensive fibrosis, vascular damage, and autoimmune events. During the last years, the number of genetic markers convincingly associated with SSc has exponentially increased. In this report, we aim to offer an updated review of the classical and novel genetic associations with SSc, analyzing the firmest and replicated signals within HLA and non-HLA genes, identified by both candidate gene and genome-wide association (GWA) studies. We will also provide an insight into the future perspectives and approaches that might shed more light into the complex genetic background underlying SSc. In spite of the remarkable advance in the field of SSc genetics during the last decade, the use of the new genetic technologies such as next generation sequencing (NGS), as well as the deep phenotyping of the study cohorts, to fully characterize the genetic component of this disease is imperative.