HLA-DR4 subtype frequencies in rheumatoid arthritis indicate that DRB1 is the major susceptibility locus within the HLA class II region

Human MHC Class II and Invariant Chain Knock-in Mice Mimic Rheumatoid Arthritis with Allele Restriction in Immune Response and Arthritis Association

Transgenic mice expressing human major histocompatibility complex class II (MHCII) risk alleles are widely used in autoimmune disease research, but limitations arise due to non-physiologic expression. To address this, physiologically relevant mouse models are established via knock-in technology to explore the role of MHCII in diseases like rheumatoid arthritis. The gene sequences encoding the ectodomains are replaced with the human DRB1*04:01 and 04:02 alleles, DRA, and CD74 (invariant chain) in C57BL/6N mice. The collagen type II (Col2a1) gene is modified to mimic human COL2. Importantly, DRB1*04:01 knock-in mice display physiologic expression of human MHCII also on thymic epithelial cells, in contrast to DRB1*04:01 transgenic mice. Humanization of the invariant chain enhances MHCII expression on thymic epithelial cells, increases mature B cell numbers in spleen, and improves antigen presentation. To validate its functionality, the collagen-induced arthritis (CIA) model is used, where DRB1*04:01 expression led to a higher susceptibility to arthritis, as compared with mice expressing DRB1*04:02. In addition, the humanized T cell epitope on COL2 allows autoreactive T cell-mediated arthritis development. In conclusion, the humanized knock-in mouse faithfully expresses MHCII, confirming the DRB1*04:01 alleles role in rheumatoid arthritis and being also useful for studying MHCII-associated diseases.

Innate and Adaptive Immunity during SARS-CoV-2 Infection: Biomolecular Cellular Markers and Mechanisms

The coronavirus 2019 (COVID-19) pandemic was caused by a positive sense single-stranded RNA (ssRNA) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, other human coronaviruses (hCoVs) exist. Historical pandemics include smallpox and influenza, with efficacious therapeutics utilized to reduce overall disease burden through effectively targeting a competent host immune system response. The immune system is composed of primary/secondary lymphoid structures with initially eight types of immune cell types, and many other subtypes, traversing cell membranes utilizing cell signaling cascades that contribute towards clearance of pathogenic proteins. Other proteins discussed include cluster of differentiation (CD) markers, major histocompatibility complexes (MHC), pleiotropic interleukins (IL), and chemokines (CXC). The historical concepts of host immunity are the innate and adaptive immune systems. The adaptive immune system is represented by T cells, B cells, and antibodies. The innate immune system is represented by macrophages, neutrophils, dendritic cells, and the complement system. Other viruses can affect and regulate cell cycle progression for example, in cancers that include human papillomavirus (HPV: cervical carcinoma), Epstein-Barr virus (EBV: lymphoma), Hepatitis B and C (HB/HC: hepatocellular carcinoma) and human T cell Leukemia Virus-1 (T cell leukemia). Bacterial infections also increase the risk of developing cancer (e.g., Helicobacter pylori). Viral and bacterial factors can cause both morbidity and mortality alongside being transmitted within clinical and community settings through affecting a host immune response. Therefore, it is appropriate to contextualize advances in single cell sequencing in conjunction with other laboratory techniques allowing insights into immune cell characterization. These developments offer improved clarity and understanding that overlap with autoimmune conditions that could be affected by innate B cells (B1+ or marginal zone cells) or adaptive T cell responses to SARS-CoV-2 infection and other pathologies. Thus, this review starts with an introduction into host respiratory infection before examining invaluable cellular messenger proteins and then individual immune cell markers.

Visual outcomes and choroidal thickness associated with human leukocyte antigen DRB1*04 in unclassifiable uveitis in Japanese patients

Purpose

Human leukocyte antigen (HLA) and immunity are related. Uveitis is also closely related to immunity. For example, the common presence of human leukocyte antigen (HLA)-DRB1*04 in the immune response is well known. The aim of this study was to investigate the relationship between visual prognosis and various HLA alleles before and after therapy in patients with unclassifiable uveitis, excluding those with Vogt-Koyanagi-Harada (VKH) disease.

Methods

This retrospective case series included 42 eyes from 22 consecutive patients with unclassifiable uveitis, excluding those with VKH disease. Visual acuity (VA), sex, refractive error, central retinal thickness (CRT), central choroidal thickness (CCT), and duration from onset to treatment were measured at initial and 6-month visits. Mean values of parameters were compared at each visit. Genotyping was performed by polymerase chain reaction amplification with sequence-specific primers.

Results

DRB1*04 showed a dominant change. No significant difference was observed in the other alleles. In DRB1*04, The mean differences in initial CCT, 6-month CCT, and 6-month VA showed statistically significant difference was found in best-corrected visual acuity (BCVA) between DRB1*04+ and DRB1*04− at the first visit. BCVA values at baseline and at the final visit were 0.13 ± 0.29 and 0.20 ± 0.36 in the DRB1*04+ and 0.00045 ± 0.20 and − 0.058 ± 0.11 in the DRB1*04− groups(p = 0.00465). Central Choroidal Thickness (CCT) values pretreatment and at the final visit after treatment were (pretreatment:361.00 ± 361.0 μm,after treatment: 286.00 ± 106.53 μm, p = 0.0174) in the DRB1*04+ group, and (pretreatment:281.3 ± 139.68 μm,after treatment:223.85 ± 99.034 μm, p = 0.0426) in the DRB1*04− group, respectively, indicating changes between baseline and the final visit. CCT was significantly greater in the DRB1*04+ group at both the initial visit and at 6 months. Multivariate analysis showed a significant difference between the presence or absence of DRB1*04 and sex.

Conclusion

HLA-DRB1*04 allele may affect visual prognosis and CCT in unclassifiable uveitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02222-9.

Adult-Onset Still's Disease Complicated by Immunoglobulin A Vasculitis and anti-CCP Antibody-Positive Arthritis

A 38-year-old male was admitted to our hospital for arthralgia, fever, skin rash, and purpura. He was diagnosed as having adult-onset Still's disease (AOSD) based on Yamaguchi's criteria. Skin biopsy revealed immunoglobulin A (IgA) vasculitis. He was also found to have anti-cyclic citrullinated peptide (CCP) antibody-positive inflammatory arthritis on a shoulder joint, however he did not fulfill classification criteria for rheumatoid arthritis. Elevated serum cytokine such as serum IL-18 supported the diagnosis of AOSD. His symptoms improved with 40 mg of prednisolone plus cyclosporin A (200 mg/day). Two years after hospitalization, AOSD was relapsed with pleurisy and hyperferritinemia. Finally, he was diagnosed with multicyclic systemic type of AOSD complicated by IgA vasculitis and seropositivity of anti-CCP antibody. Clinicians need to consider the complication of multiple rheumatic diseases, even if the disease-specific autoantibody is positive.

A systematic review and meta-analysis of observational studies on the association between animal protein sources and risk of rheumatoid arthritis

OBJECTIVE

The aim of this study was to investigate the linear and nonlinear dose-response associations of animal-based dietary protein intake and risk of developing rheumatoid arthritis (RA).

METHODS

A systematic search of MEDLINE, Scopus and Embase was conducted up to October 2020. Observational studies that report risk estimates of RA for animal-based protein consumption were included. We calculated pooled relative risks (RRs) by using a random-effects model. Linear and non-linear dose-response analyses were performed to examine the dose-response relations between animal-based protein consumption and RA.

RESULTS

Seven cohort studies (n = 457,554) with 3545 incident cases and six case-control studies with 3994 cases and 5252 controls were identified. Highest compared with the lowest category of fish consumption was inversely associated with risk of RA (RR: 0.89; 95% CI, 0.80 to 0.99; I² = 0%, n = 10). Also, a 100 g/day increment in fish intake was associated with a 15% decreased risk of RA. Dose-response analysis showed a modest U-shaped association between fish consumption and incidence of RA, with the lowest risk at a fish intake of 20-30 g/day (P_{non-linearity} = 0.04). We found no significant association between consumption of red meat, poultry or dairy and the risk of RA.

CONCLUSION

The present study revealed a significant reverse association between fish consumption and risk of RA. While we observed no association between red meat, dairy or poultry consumption and risk of RA. Further well-designed prospective studies are needed to support our findings.

The role of posttranslational modifications in generating neo-epitopes that bind to rheumatoid arthritis-associated HLA-DR alleles and promote autoimmune T cell responses

While antibodies to citrullinated proteins have become a diagnostic hallmark in rheumatoid arthritis (RA), we still do not understand how the autoimmune T cell response is influenced by these citrullinated proteins. To investigate the role of citrullinated antigens in HLA-DR1- and DR4-restricted T cell responses, we utilized mouse models that express these MHC-II alleles to determine the relationship between citrullinated peptide affinity for these DR molecules and the ability of these peptides to induce a T cell response. Using a set of peptides from proteins thought to be targeted by the autoimmune T cell responses in RA, aggrecan, vimentin, fibrinogen, and type II collagen, we found that while citrullination can enhance the binding affinity for these DR alleles, it does not always do so, even when in the critical P4 position. Moreover, if peptide citrullination does enhance HLA-DR binding affinity, it does not necessarily predict the generation of a T cell response. Conversely, citrullinated peptides can stimulate T cells without changing the peptide binding affinity for HLA-DR1 or DR4. Furthermore, citrullination of an autoantigen, type II collagen, which enhances binding affinity to HLA-DR1 did not enhance the severity of autoimmune arthritis in HLA-DR1 transgenic mice. Additional analysis of clonal T cell populations stimulated by these peptides indicated cross recognition of citrullinated and wild type peptides can occur in some instances, while in others cases the citrullination generates a novel T cell epitope. Finally, cytokine profiles of the wild type and citrullinated peptide stimulated T cells unveiled a significant disconnect between proliferation and cytokine production. Altogether, these data demonstrate the lack of support for a simplified model with universal correlation between affinity for HLA-DR alleles, immunogenicity and arthritogenicity of citrullinated peptides. Additionally they highlight the complexity of both T cell receptor recognition of citrulline as well as its potential conformational effects on the peptide:HLA-DR complex as recognized by a self-reactive cell receptor.

Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis

The development of inflammatory arthritis in patients receiving immune checkpoint inhibitor therapy is increasingly recognized due to the growing use of these drugs for the treatment of cancer. This represents an important opportunity not only to define the mechanisms responsible for the development of this immune-related adverse event and to ultimately predict or prevent its development, but also to provide a unique window into early events in the development of inflammatory arthritis. Knowledge gained through the study of this patient population, for which the inciting event is known, could shed light into the pathogenesis of autoimmune arthritis. This review will highlight the clinical and immunologic features of these entities to define common elements for future study.

HLA associations in inflammatory arthritis: emerging mechanisms and clinical implications

Our understanding of the mechanisms underlying HLA associations with inflammatory arthritis continues to evolve. Disease associations have been refined, and interactions of HLA genotype with other genes and environmental risk factors in determining disease risk have been identified. This Review provides basic information on the genetics and molecular function of HLA molecules, as well as general features of HLA associations with disease. Evidence is discussed regarding the various peptide-dependent and peptide-independent mechanisms by which HLA alleles might contribute to the pathogenesis of three types of inflammatory arthritis: rheumatoid arthritis, spondyloarthritis and systemic juvenile idiopathic arthritis. Also discussed are HLA allelic associations that shed light on the genetic heterogeneity of inflammatory arthritides and on the relationships between adult and paediatric forms of arthritis. Clinical implications range from improved diagnosis and outcome prediction to the possibility of using HLA associations in developing personalized strategies for the treatment and prevention of these diseases.

The Contribution of Major Histocompatibility Complex Class II Genes to an Association with Autoimmune Diseases

Genetic studies of patients with autoimmune diseases have shown that one of the most important roles in the developing of these diseases is played by a cluster of genes of the major histocompatibility complex (MHC), as compared with other genome areas. Information on the specific contribution of MHC alleles, mostly MHC class II ones, to the genetic predisposition to autoimmune diseases is crucial for understanding their pathogenesis. This review dwells on the most relevant aspects of this problem: namely, the correlation between carriage of certain MHC II alleles and an increased (positively associated allele) or reduced (negatively associated allele) probability of developing the most common autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, autoimmune thyroiditis, etc. The most universal haplotypes, DR3-DQ2 and DR4-DQ8, are positively associated with many of these diseases, while the universal allele HLA-DRB1*0701 is protective.

Multiple hit infection and autoimmunity: the dysbiotic microbiota-ACPA connection in rheumatoid arthritis

PURPOSE OF REVIEW

This review highlights the most recent data obtained in this field and provides clues toward the better understanding of the close interplay between microbiota and host, leading to autoimmune diseases.

RECENT FINDINGS

A well-described model of microbiota/host interaction of relevance to autoimmunity is linking anti-citrullinated peptide antibody positive rheumatoid arthritis and alterations of microbiota largely concentrating on Porphyromonas gingivalis and more recently of Aggregatibacter actinomycetemcomitans and Prevotella copri.

SUMMARY

The perception of the classical link between microbial infection and development of autoimmune disease has evolved to the more recent concept of the connection between the microbiome/dysbiosis and breaking of immunological tolerance.

Selective Inhibitors of T Cell Receptor Recognition of Antigen-MHC Complexes for Rheumatoid Arthritis

Autoreactive T cells specific to human collagen type II have a crucial role in the development of rheumatoid arthritis (RA) in the context of MHC class II allele HLA-DRB1-*04. The protein-protein interactions between the T cell receptor (TCR) and the type II collagen bound to the allele MHC of class II may thus represent the target for the development of new drugs against RA. In this study, a structure-based pharmacophore model for potential small molecule inhibitors was developed from protein-protein interface structure. The 3D model obtained was used for a virtual screening workflow, which resulted in three hits for experimental follow up. Three compounds have been identified that interfere with the TCR/collagenII-MHCII (K _i values below 10 μM) and open up new possibilities in the treatment of RA.

Curcumin for the Management of Periodontitis and Early ACPA-Positive Rheumatoid Arthritis: Killing Two Birds with One Stone

We propose curcumin as a preventive measure to avoid/manage periodontitis (PD), and as a natural immunosuppressant for rheumatoid arthritis (RA). PD, mainly caused by Porphyromonas gingivalis forming biofilm and leading to tooth decay, is a major public health issue and a risk factor for the development of RA in humans. P. gingivalis is able to trigger experimental autoimmune arthritis in animal models and in humans can induce citrullinated peptides, which not only are a source of anti-citrullinated antibodies (ACPAs), but also participate in autoreactive responses and disease development. Curcumin appears to have efficient anti-bacterial activity against P. gingivalis infection and biofilm formation. In addition to antibacterial, anti-oxidant, and anti-inflammatory action, curcumin exerts unique immunosuppressant properties via the inhibition of Th17 pro-inflammatory responses and promotion of regulatory T cells, thus suppressing autoimmunity. We introduce curcumin as a natural product for the management of both PD and RA-related autoreactivity, possibly also as a preventive measure in early RA or individuals at high risk to develop RA.

The Infectious Basis of ACPA-Positive Rheumatoid Arthritis

Rheumatoid arthritis (RA) is associated with HLA-DRB1 shared epitope (HLA-DRB1SE) and anti-citrullinated protein autoantibodies (ACPAs). ACPAs precedes the onset of clinical and subclinical RA. There are strong data for three infectious agents as autoimmunity triggers in RA, namely Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans causes of periodontal disease (PD), and Epstein-Barr virus (EBV). P. gingivalis expresses arginine gingipains, that cleave proteins at the arginine residues, and peptidyl arginine deiminase (PPAD), which citrullinates arginine residues of proteins, thus forming neoantigens that lead to ACPA production. Peripheral blood plasmablasts from ACPA+RA patients produce ACPAs the majority of which react against P. gingivalis. A. actinocycetemcomitans produces leukotoxin A, a toxin that forms pores in the neutrophil membranes and leads to citrullination and release of citrullinated autoantigens in the gums. EBV can infect B cells and epithelial cells and resides as latent infection in resting B cells. Abs against citrullinated peptides derived from EBV nuclear antigen appear years before RA and cross-react with human citrullinated fibrin. Citrullinated proteins are potential arthritogenic autoantigens in RA. The conversion of arginine to citrulline increases the peptide binding affinity to HLA-DRB1SE. Also, citrullinated fibrinogen induces arthritis in HLA-DRB1^*0401 transgenic mice, and transfer of their splenic T cells causes arthritis to recipient mice.

Targeting the programmed cell death-1 pathway in rheumatoid arthritis

Since the introduction of TNF-α inhibitors and other biologic agents, the clinical outcome for many treated rheumatoid arthritis patients has significantly improved. However, there are still a substantial proportion of patients that are intolerant, or have inadequate responses, with current agents that have become the standards of care. While the majority of these agents are designed to affect the inflammatory features of the disease, there are also agents in the clinic that instead target lymphocyte subsets (e.g., rituximab) or interfere with lymphocyte co-receptor signaling pathways (e.g., abatacept). Due in part to their ability to orchestrate downstream inflammatory responses that lead to joint damage and disease progression, pathogenic expansions of T and B lymphocytes are appreciated to play key roles in the pathogenesis of rheumatoid arthritis. New insights into immune regulation have suggested novel approaches for the pharmacotherapeutic targeting of lymphocytes. In this review, we discuss deepening insights into human genetics and our understanding of the interface with rheumatoid arthritis pathogenesis providing a strong rationale for exploiting the co-inhibitory receptor programmed cell death-1 signaling pathway as a better approach for the treatment of this chronic, often progressive destructive joint disease.

Identification and Validation of SAA4 as a Rheumatoid Arthritis Prescreening Marker by Liquid Chromatography Tandem-mass Spectrometry

Rheumatoid arthritis (RA) is a chronic autoimmune disease that progresses into systemic inflammation and joint deformity. RA diagnosis is a complicated procedure, and early diagnostic methods are insufficient. Therefore, in this study, we attempted to identify new markers to improve the accuracy of RA prescreening. e identified differentially expressed proteins (DEPs) by using liquid chromatography tandem-mass spectrometry in health-prescreening sera with high rheumatoid factor (RF) values, and compared the findings with those from sera with normal RF values. We identified 93 DEPs; of these, 36 were upregulated, and 57 were downregulated in high-RF sera. Pathway analysis revealed that these DEPs were related to immune responses. Additionally, four DEPs were statistically analyzed by proteomic analysis; of these, SAA4 was significantly validated in individual enzyme-linked immunosorbent assays. Moreover, SAA4 was significantly upregulated in RA patients (n = 40, 66.43 ± 12.97 ng/mL) compared with normal controls (n = 40, 4.79 ± 0.95 ng/mL) and had a higher area under the curve than C-reactive protein. Thus, we identified SAA4 as a protein that was positively correlated with RF and RA. SAA4 may represent a novel prescreening marker for the diagnosis of RA.

The autoimmunity-oral microbiome connection

To date, there is a major effort in deciphering the role of complex microbial communities, especially the oral and gut microbiomes, in the pathogenesis of various diseases. Increasing evidence indicates a key role for the oral microbiome in autoimmune diseases. In this review article, we discuss links of the oral microbiota to a group of autoimmune diseases, that is, Sjögren's syndrome (SS), systemic lupus erythematosus (SLE), Crohn's disease (CD), and rheumatoid arthritis (RA). We particularly focus on factors that affect the balance between the immune system and the composition of microbiota leading to dysbiosis, loss of tolerance and subsequent autoimmune disease progression and maintenance.

Infections as a cause of autoimmune rheumatic diseases

Exogenous and endogenous environmental exposures and particularly infections may participate in the breakage of tolerance and the induction of autoimmunity in rheumatic diseases. Response to infections apparently occurs years before clinical manifestations and features of autoimmunity, such as autoantibodies, are detected years before clinical manifestations in autoimmune rheumatic diseases. In this review, we summarize the current evidence for a potential causal link between infectious agents and rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, Sjogren’s syndrome and ANCA-associated vasculitis.

Of the multiple mechanisms leading to type 1 diabetes, T cell receptor revision may play a prominent role (is type 1 diabetes more than a single disease?)

A single determinant factor for autoimmunity does not exist; disease development probably involves contributions from genetics, the environment and immune dysfunction. Type 1 diabetes is no exception. Genomewide-associated studies (GWAS) analysis in T1D has proved disappointing in revealing contributors to disease prediction; the only reliable marker has been human leucocyte antigen (HLA). Specific HLAs include DR3/DR4/DQ2/DQ8, for example. Because HLA molecules present antigen to T cells, it is reasonable that certain HLA molecules have a higher affinity to present self-antigen. Recent studies have shown that additional polymorphisms in HLA that are restricted to autoimmune conditions are further contributory. A caveat is that not all individuals with the appropriate 'pro-autoimmune' HLA develop an autoimmune disease. Another crucial component is autoaggressive T cells. Finding a biomarker to discriminate autoaggressive T cells has been elusive. However, a subset of CD4 helper cells that express the CD40 receptor have been described as becoming pathogenic. An interesting function of CD40 on T cells is to induce the recombination-activating gene (RAG)1/RAG2 T cell receptor recombination machinery. This observation is contrary to immunology paradigms that changes in TCR molecules cannot take place outside the thymic microenvironment. Alteration in TCR, called TCR revision, not only occurs, but may help to account for the development of autoaggressive T cells. Another interesting facet is that type 1 diabetes (T1D) may be more than a single disease; that is, multiple cellular components contribute uniquely, but result ultimately in the same clinical outcome, T1D. This review considers the process of T cell maturation and how that could favor auto-aggressive T cell development in T1D. The potential contribution of TCR revision to autoimmunity is also considered.

Recent Advances in Defining the Genetic Basis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory arthritis and exhibits genetic overlap with other autoimmune and inflammatory disorders. Although predominant associations with the HLA-DRB1 locus have been known for decades, recent data have revealed additional insight into the likely causative variants within HLA-DRB1 as well as within other HLA loci that contribute to disease risk. In addition, more than 100 common variants in non-HLA loci have been implicated in disease susceptibility. Genetic factors are involved not only in the development of RA, but also with various disease subphenotypes, including production and circulating levels of autoantibodies and joint destruction. The major current challenge is to integrate these new data into a precise understanding of disease pathogenesis, including the critical cell types and molecular networks involved as well as interactions with environmental factors. We predict that delineating the functional effects of genetic variants is likely to drive new diagnostic and therapeutic approaches to the disease.

Infectomics and autoinfectomics: a tool to study infectious-induced autoimmunity

The exposome represents all exogenous and endogenous environmental exposures that begin at preconception and carry on throughout life, while the microbiome reflects the microbial component of the exposome. We recently introduced the concept of infectome and autoinfectome as a means of studying the totality of infections throughout life that participate in the induction as well as the progression of autoimmune diseases in an affected individual. The investigation of the autoinfectome could help us understand why some patients develop more than one autoimmune disease, a phenomenon also known as mosaic of autoimmunity. It could also explain the infectious and autoantibody burden of various autoimmune rheumatic diseases. The close interplay between infections and the immune system should be studied over time, long before the onset of autoaggression and autoimmunity. Tracking down each individual's exposure to infectious agents (as defined by the autoinfectome) would be important for the establishment of a causative link between infection and autoimmunity.

Antigen Presentation, Autoantigens, and Immune Regulation in Multiple Sclerosis and Other Autoimmune Diseases

Antigen presentation is in the center of the immune system, both in host defense against pathogens, but also when the system is unbalanced and autoimmune diseases like multiple sclerosis (MS) develop. It is not just by chance that a major histocompatibility complex gene is the major genetic susceptibility locus in MS; a feature that MS shares with other autoimmune diseases. The exact etiology of the disease, however, has not been fully understood yet. T cells are regarded as the major players in the disease, but most probably a complex interplay of altered central and peripheral tolerance mechanisms, T-cell and B-cell functions, characteristics of putative autoantigens, and a possible interference of environmental factors like microorganisms are at work. In this review, new data on all these different aspects of antigen presentation and their role in MS will be discussed, probable autoantigens will be summarized, and comparisons to other autoimmune diseases will be drawn.

B Cells with Regulatory Function in Animal Models of Autoimmune and Non-Autoimmune Diseases

Although the identification of B cell subsets with negative regulatory functions and the definition of their mechanisms of action are recent events, the important negative regulatory roles of B cells in immune responses are now broadly recognized. There is an emerging appreciation for the pivotal role played by B cells in several areas of human diseases including autoimmune diseases and non-autoimmune diseases such as parasite infections and cancer. The recent research advancement of regulatory B cells in human disease coincides with the vastly accelerated pace of research on the bridging of innate and adaptive immune system. Current study and our continued research may provide better understanding of the mechanisms that promote regulatory B10 cell function to counteract exaggerated immune activation in autoimmune as well as non-autoimmune conditions. This review is focused on the current knowledge of BREG functions studied in animal models of autoimmune and non-autoimmune diseases.

DRB1*0402 may influence arthritis by promoting naive CD4+ T-cell differentiation in to regulatory T cells

HLA-DRB1*0401 expression in humans has been associated with a predisposition to developing rheumatoid arthritis (RA) and collagen-induced arthritis (CIA), while HLA-DRB1*0402 is not associated with susceptibility. Here, we determined if mice transgenic (Tg) for human *0401 have a CD4+ T-cell repertoire that predetermines proinflammatory cytokine production. The data show that both *0401 and *0402 Tg mice can produce TH1/TH17 cytokines, although the kinetics of response may be different. However, in the context of antigen-specific responses in a CIA model, *0402 Tg mice generate a TH2 response that may explain their resistance to developing arthritis. In addition, a significant subset of naïve CD4+ T cells from *0402 Tg mice can be activated in polarizing conditions to differentiate into Treg cells that produce IFN-γ. *0401 Tg mice harbor memory CD4+ T cells that differentiate into IL-17(+) cells in various polarizing conditions. Our data suggest that *0401 Tg mice generate a strong immune response to lipopolysaccharide and may be efficient in clearing infection, and may *0401 have been evolutionarily selected for this ability. Autoimmunity, such as RA, could likely be a bystander effect of the cytokine storm that, along with the presence of low Treg-cell numbers in *0401 Tg mice, causes immune dysregulation.

Anti-citrullinated peptides as autoantigens in rheumatoid arthritis-relevance to treatment

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by the presence of rheumatoid factor (RF) and anti-citrullinated protein/peptide autoantibodies (ACPAs). Citrulline derives from arginine by peptidyl arginine deiminases, and ACPAs are directed against different citrullinated antigens, including fibrinogen, fibronectin, α-enolase, collagen type II, histones. ACPAs are present in two thirds of RA patients have higher specificity than RF for RA, and are associated with joint radiographic damage and extra-articular manifestations and they are detected years before the onset clinical arthritis. Recent studies suggest that citrullinated antigens are most likely arthritogenic autoantigens in RA. ACPA production is associated with the HLA-DRB1 shared epitope (HLA-DRB1 SE) and accounts for the well-known RA-HLA-DRB1 SE association, as T cells recognize citrullinated peptides. Smoking and periodontitis, known environmental risk factors for RA promote protein citrullination and ACPA production. Cirullinated proteins are capable of inducing arthritis in transgenic mice carrying HLA-DRB1 SE genes, and ACPAs induce macrophage TNF-α production, osteoclastogenesis and complement activation. They also induce the formation of neutrophil extracellular traps (NETs). NETs, increased in RA, are a source of citrullinated autoantigens in RA and induce fibroblast interleukin-8 production. This knowledge is likely to have therapeutic implications, as there is a need of matching therapy with patient profile. Abatacept, a T cell activation modulator, is the best therapy for ACPA(+) RA patients, although clinical data are sparse at present. Rituximab, a monoclonal antibody that depletes B cells, is also the best therapy for ACPA(+) RA patients, and clinical data support this view.

Rheumatoid arthritis in the Women's Health Initiative: methods and baseline evaluation

Second-generation assays for anti-cyclic citrullinated peptide (anti-CCP), a highly sensitive and specific marker for rheumatoid arthritis (RA), have redefined the epidemiology of RA. In the Women's Health Initiative (WHI) RA study (2009-2011), we evaluated the prevalence of anti-CCP positivity among 15,691 (10.2% of 161,808) WHI participants aged 50-79 years who reported RA. Using stored baseline specimens, we measured serum anti-CCP, rheumatoid factor (RF), and antinuclear antibody in a defined sample of 9,988 of black, white, and Hispanic women. In a subset of women, we measured plasma cytokine levels and number of copies of the human leukocyte antigen (HLA)-DRB1 (HLA-DRB1) shared epitope in DNA by means of Luminex polymerase chain reaction typing (Luminex Corporation, Austin, Texas). We validated classification of probable clinical RA in 2 clinics as anti-CCP positivity or self-reported validated use of disease-modifying antirheumatic drugs (DMARDs). The prevalence of anti-CCP positivity was 8.1%, and the prevalence of RF positivity was approximately 16.0%. DMARD use including prednisone was reported by 1,140 (11.4%) participants (841 excluding prednisone) but by 57.5% of anti-CCP-positive women. The prevalence of 2 shared epitopes was also much higher for anti-CCP-positive women (18.2%, as opposed to only 5.5% for women with anti-CCP-negative DMARD-positive RA and 6.6% for anti-CCP-negative, RF-negative DMARD nonusers). Median cytokine levels were much higher for anti-CCP-positive/RF-positive women. Women with anti-CCP-positive RA and anti-CCP-negative RA had different characteristics with regard to HLA shared epitope, cigarette smoking, and inflammation (cytokines).

Association between IgA deficiency & other autoimmune conditions: a population-based matched cohort study

PURPOSE

To examine autoimmune disorders in patients with IgA deficiency compared with the general population.

METHODS

Nationwide prospective population-based cohort study. Through six university hospitals in Sweden we identified 2100 individuals with IgA deficiency (IgA levels < .07 g/L) diagnosed between 1980 and 2011. Each patient with IgA deficiency was matched on age, sex, place of residence, and year of diagnosis with up to 10 general population controls (n = 18,653). Data on nine autoimmune disorders were retrieved from the Swedish National Patient Register (including inpatient and non-primary outpatient care). Autoimmune disorders were defined as having at least two visits listing the relevant international classification of disease (ICD) code as main diagnosis. Prevalences and prevalence ratios (PRs) were calculated.

RESULTS

Individuals with IgA deficiency more often had celiac disease (6.7 % vs. 0.19 % in controls) and type 1 diabetes (5.9 % vs. 0.57 %) corresponding to a 35-fold higher PR for celiac disease and 10-fold higher for type 1 diabetes. Also for the other autoimmune diseases did we see statistically significantly elevated prevalences and PRs (juvenile idiopathic arthritis (0.76 % vs. 0.09 % in controls, PR = 8.9), systemic lupus erythematosus (0.57 % vs. 0.06 %; PR = 8.9), inflammatory bowel disease (3.9 % vs. 0.81 %; PR = 5.0; specifically Crohn's disease (2.4 % vs. 0.42 %; PR = 5.7) and ulcerative colitis (1.7 % vs. 0.46 %; PR = 3.9)), hypothyreosis (0.76 % vs. 0.16 %; PR = 4.6), rheumatoid arthritis (2.2 % vs. 0.50 %; PR = 4.5), and hyperthyreosis (1.7 % vs. 0.43 %; PR = 3.9), but not with myasthenia gravis (0.05 % vs. 0.02 %; PR = 3.0).

CONCLUSIONS

Individuals with IgA deficiency have a higher prevalence of several other autoimmune disorders.

Design of peptide immunotherapies for MHC Class-II-associated autoimmune disorders

Autoimmune disorders, that occur when autoreactive immune cells are induced to activate their responses against self-tissues, affect one percent of the world population and represent one of the top 10 leading causes of death. The major histocompatibility complex (MHC) is a principal susceptibility locus for many human autoimmune diseases, in which self-tissue antigens providing targets for pathogenic lymphocytes are bound to HLA molecules encoded by disease-associated alleles. In spite of the attempts to design strategies for inhibition of antigen presentation targeting the MHC-peptide/TCR complex via generation of blocking antibodies, altered peptide ligands (APL), or inhibitors of costimulatory molecules, potent therapies with minimal side effects have yet to be developed. Copaxone (glatiramer acetate, GA) is a random synthetic amino acid copolymer that reduces the relapse rate by about 30% in relapsing-remitting multiple sclerosis (MS) patients. Based on the elucidated binding motifs of Copaxone and of the anchor residues of the immunogenic myelin basic protein (MBP) peptide to HLA-DR molecules, novel copolymers have been designed and proved to be more effective in suppressing MS-like disease in mice. In this report, we describe the rationale for design of second-generation synthetic random copolymers as candidate drugs for a number of MHC class-II-associated autoimmune disorders.

Structural basis for self-recognition by autoimmune T-cell receptors

T-cell receptors (TCRs) recognize peptides presented by major histocompatibility complex molecules (pMHC) to discriminate between foreign and self-antigens. Whereas T-cell recognition of foreign peptides is essential for protection against microbial pathogens, recognition of self-peptides by T cells that have escaped negative selection in the thymus can lead to autoimmune disease. Structural studies of autoimmune TCR-pMHC complexes have provided insights into the mechanisms underlying self-recognition and escape from thymic deletion. Two broad categories of self-reactive TCRs can be clearly distinguished: (i) TCRs with altered binding topologies to self-pMHC and (ii) TCRs that bind self-pMHC in the canonical diagonal orientation, but where there are structural defects or suboptimal anchors in the self-ligand. For both categories, however, the overall stability of the autoimmune TCR-pMHC complex is markedly reduced compared to anti-microbial complexes, allowing the autoreactive T cells to evade negative selection, yet retain the ability to be activated by self-antigens in target organs. Additionally, the structures provide insights into TCR cross-reactivity, which can contribute to autoimmunity by increasing the likelihood of self-pMHC recognition. Efforts are now underway to understand the impact of structural alterations in autoimmune TCR-pMHC complexes on higher order assemblies involved in TCR signaling, as well as on immunological synapse formation.

IL-10-producing regulatory B cells (B10 cells) in autoimmune disease

B cell abnormalities contribute to the development and progress of autoimmune disease. Traditionally, the role of B cells in autoimmune disease was thought to be predominantly limited to the production of autoantibodies. Nevertheless, in addition to autoantibody production, B cells have other functions potentially relevant to autoimmunity. Such functions include antigen presentation to and activation of T cells, expression of co-stimulatory molecules and cytokine production. Recently, the ability of B cells to negatively regulate cellular immune responses and inflammation has been described and the concept of regulatory B cells has emerged. A variety of cytokines produced by regulatory B cell subsets have been reported, with IL-10 being the most studied. In this review, this specific IL-10-producing subset of regulatory B cells has been labeled B10 cells to highlight that the regulatory function of these rare B cells is mediated by IL-10, and to distinguish them from other B cell subsets that regulate immune responses through different mechanisms. B10 cells are a functionally defined subset currently identified only by their competency to produce and secrete IL-10 following appropriate stimulation. Although B10 cells share surface markers with other previously defined B cell subsets, currently there is no cell surface or intracellular phenotypic marker or set of markers unique to B10 cells. The recent discovery of an effective way to expand B10 cells ex vivo opens new horizons in the potential therapeutic applications of this rare B cell subset. This review highlights the current knowledge on B10 cells and discusses their potential as novel therapeutic agents in autoimmunity.

Structure-based prediction of Major Histocompatibility Complex (MHC) epitopes

Because of the enormous diversity of both MHC proteins and peptide epitopes, computational epitope prediction methods are needed in order to supplement limited experimental data. These prediction methods are useful for guiding experiments and have many potential biomedical applications. Unlike popular sequence-based methods, structure-based epitope prediction methods can predict epitopes for multiple MHC types with highly distinct peptide binding propensities. In this chapter, we describe in detail our previously developed structure-based epitope prediction methods for both class I and class II MHC proteins. We also discuss the relative advantages and disadvantages of sequence-based versus structure-based methods and how to evaluate prediction performance.

What Have We Learned about the Pathogenesis of Rheumatoid Arthritis from TNF-Targeted Therapy?

Studies of cytokine regulation in rheumatoid arthritis led to the development of TNFα inhibitors which are now used for a number of indications, including rheumatoid arthritis, inflammatory bowel disease, psoriasis, psoriatic arthritis, and ankylosing spondylitis. The widespread use of biologics in the clinic offers unique opportunities for probing disease pathogenesis and this paper provides an overview of rheumatoid arthritis, with a particular emphasis on the impact of anti-TNFα therapy on pathogenetic mechanisms. An overview is also provided on the most commonly used animal models that mimic RA, including adjuvant-induced arthritis, collagen-induced arthritis, TNFα-transgenic mice, and the K/BxN and SKG models. These models have led to significant discoveries relating to the importance of pro-inflammatory cytokines in the pathogenesis of rheumatoid arthritis, resulting from disregulation of the normally finely tuned balance of pro- and anti-inflammatory cytokine signalling. In addition, experimental evidence is discussed suggesting how genetic and environmental factors can contribute to disease susceptibility. The role of effector and regulatory T cells is discussed in the light of the relatively disappointing therapeutic effects of T cell modifying agents such as anti-CD4 antibody and cyclosporin. It is concluded that comprehensive analyses of mechanisms of action of biologics and other drugs entering the clinic will be essential to optimise therapy, with the ultimate aim of providing a cure.

Association of MIF-173G/C and MBL2 codon 54 gene polymorphisms with rheumatoid arthritis: a meta-analysis

The aim of this study was to evaluate the association between macrophage migration inhibitory factor (MIF) -173G/C (rs755622), mannose-binding lectin (MBL2) exon 1 codon 54 (rs1800450) gene polymorphisms and rheumatoid arthritis (RA) susceptibility in ethnically different populations. A meta-analysis was conducted (allelic contrast, the additive model, the dominant model and the recessive model) on the MIF-173G/C polymorphism across five studies (four European and one Asian studies), and the MBL2 codon 54 polymorphism with five studies (four Asian and one European studies), respectively. Meta-analysis indicated an association between the MIF-173G/C in all study subjects in allelic contrast (OR=1.19, 95%CI: 1.05-1.35, P=0.001), the additive model (OR=1.68, 95CI: 1.13-2.49, P=0.001), the dominant model (OR=1.17, 95CI: 1.01-1.35, P=0.003), the recessive model (OR=1.63, 95CI: 1.10-2.42, P=0.001). While stratified by ethnicity with European populations, an association was found in allelic contrast (OR=1.20, 95CI: 1.04-1.38, P=0.002), the additive model (OR=1.85, 95CI: 1.19-2.88, P=0.001), the dominant model (OR=1.20, 95CI: 1.02-1.41, P=0.003). With respect to MBL2 codon 54 polymorphism and RA, no association was found in all study subjects in all comparisons, but there was an association while stratified by ethnicity with Asian populations in the dominant model (OR=1.50, 95CI: 1.01-2.23, P=0.007). In conclusion, the present study suggests that the MIF-173G/C polymorphism is associated with RA susceptibility, but the MBL2 codon 54 polymorphism is not associated with RA.

Lack of association of TLR4 polymorphisms with susceptibility to rheumatoid arthritis and ankylosing spondylitis: a meta-analysis

OBJECTIVE

The aim of the study was to determine whether polymorphisms of toll-like receptor 4 (TLR4) confer susceptibility to rheumatoid arthritis (RA) and ankylosing spondylitis (AS).

METHODS

A meta-analysis was conducted on the association between the D299G/T399I polymorphisms and RA/AS (when available) using (1) the allelic contrast, (2) the recessive, (3) the dominant, and (4) the additive models.

RESULTS

A total of eleven relevant studies met the inclusion criteria were identified, including RA: D299G (six studies), T399I (three studies); AS: D299G (five studies), T399I (four studies). Meta-analysis was performed with fixed/random effect models. Overall, no significant RA/AS risk was found in all genetic models when all studies were pooled into the meta-analysis (P>0.05).

CONCLUSIONS

The present study might suggest that TLR4 D299G/T399I polymorphisms are not associated with RA/AS susceptibility.

HLA-DRβ1*04 typing by simple in-house PCR-SSP technique for rheumatoid arthritis patients

A strong association between rheumatoid arthritis (RA) and human leukocyte antigen (HLA) has been observed in many different populations and that accounts for approximately one-third of the genetic component of RA susceptibility. The greatest effect comes from DRβ1 gene where the strongest association has been found with DRβ1*04 (DR4) allele. As serology has some disadvantages over polymerase chain reaction (PCR)-based techniques and commercially available PCR-based kits are expensive, this study was aimed to standardize simple in-house PCR-SSP technique. Accuracy of this test was further checked with standard PCR-SSOP (RLS) results. The frequency HLA-DRβ1*04 was significantly increased among RA patients when compared with normal controls. In this study, a very simple, convenient and more cost-effective in-house PCR-SSP technique was standardized for HLA-DRβ1*04 typing that is helpful to RA diagnosis in developing countries like India, which can be used as a good screening test.

A genome-wide homozygosity association study identifies runs of homozygosity associated with rheumatoid arthritis in the human major histocompatibility complex

Rheumatoid arthritis (RA) is a chronic inflammatory disorder with a polygenic mode of inheritance. This study examined the hypothesis that runs of homozygosity (ROHs) play a recessive-acting role in the underlying RA genetic mechanism and identified RA-associated ROHs. Ours is the first genome-wide homozygosity association study for RA and characterized the ROH patterns associated with RA in the genomes of 2,000 RA patients and 3,000 normal controls of the Wellcome Trust Case Control Consortium. Genome scans consistently pinpointed two regions within the human major histocompatibility complex region containing RA-associated ROHs. The first region is from 32,451,664 bp to 32,846,093 bp (−log10(p)>22.6591). RA-susceptibility genes, such as HLA-DRB1, are contained in this region. The second region ranges from 32,933,485 bp to 33,585,118 bp (−log10(p)>8.3644) and contains other HLA-DPA1 and HLA-DPB1 genes. These two regions are physically close but are located in different blocks of linkage disequilibrium, and ∼40% of the RA patients' genomes carry these ROHs in the two regions. By analyzing homozygote intensities, an ROH that is anchored by the single nucleotide polymorphism rs2027852 and flanked by HLA-DRB6 and HLA-DRB1 was found associated with increased risk for RA. The presence of this risky ROH provides a 62% accuracy to predict RA disease status. An independent genomic dataset from 868 RA patients and 1,194 control subjects of the North American Rheumatoid Arthritis Consortium successfully validated the results obtained using the Wellcome Trust Case Control Consortium data. In conclusion, this genome-wide homozygosity association study provides an alternative to allelic association mapping for the identification of recessive variants responsible for RA. The identified RA-associated ROHs uncover recessive components and missing heritability associated with RA and other autoimmune diseases.

HLA-DRB1 may be antagonistically regulated by the coordinately evolved promoter and 3'-UTR under stabilizing selection

HLA-DRB1 is the most polymorphic MHC (major histocompatibility complex) class II gene in human, and plays a crucial role in the development and function of the immune system. Extensive polymorphisms exist in the promoter and 3'-UTR of HLA-DRB1, especially a LTR (Long terminal repeat) element in the promoter, which may be involved in the expression regulation. However, it remains unknown how the polymorphisms in the whole promoter region and 3'-UTR to regulate the gene expression. In this study, we investigated the extensive polymorphisms in the HLA-DRB1 promoter and 3'-UTR, and how these polymorphisms affect the gene expression in both independent and jointly manners. It was observed that most of the haplotypes in the DRB1 promoter and 3'-UTR were clustered into 4 conserved lineages (H1, H2, H3 and H4), and showed high linkage disequilibrium. Compared with H1 and H2 lineage, a LTR element in the promoter of H3 and H4 lineage significantly suppressed the promoter activity, whereas the activity of the linked 3'-UTR increased, leading to no apparent difference in the final expression product between H1/H2 and H3/H4 lineage. Nevertheless, compared with the plasmid with a promoter and 3'-UTR from the same lineage, the recombinant plasmid with a promoter from H2 and a 3'-UTR from H3 showed about double fold increased luciferase activity, Conversely, the recombinant plasmid with a promoter from H3 and a 3'-UTR from H2 resulted in about 2-fold decreased luciferase activity. These results indicate that the promoter and 3'-UTR of HLA-DRB1 may antagonistically regulate the gene expression, which may be subjected to stabilizing selection. These findings may provide a novel insight into the mechanisms of the diseases associated with HLA-DRB1 genes.

A functional polymorphism in B and T lymphocyte attenuator is associated with susceptibility to rheumatoid arthritis

Inhibitory coreceptors are thought to play important roles in maintaining immunological homeostasis, and a defect in the negative signals from inhibitory coreceptors may lead to the development of autoimmune diseases. We have recently identified B and T lymphocyte attenuator (BTLA), a new inhibitory coreceptor expressed on immune cells, and we suggest that BTLA may be involved in the development of autoimmune diseases using BTLA-deficient mice. However, the role of BTLA in the pathogenesis of autoimmune diseases in humans remains unknown. We, therefore, examined the possible association between BTLA and rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and Sjögren's syndrome (SS) by conducting a case-control genetic association study. We found that 590C single-nucleotide polymorphism (SNP) of BTLA gene was significantly associated with susceptibility to RA, but not to SLE or SS. Furthermore, RA patients bearing this 590C SNP developed the disease significantly earlier than the patients without this allele. We also found that BTLA with 590C allele lacked the inhibitory activity on concanavalin A- and anti-CD3 Ab-induced IL-2 production in Jurkat T cells. These results suggest that BTLA is an RA-susceptibility gene and is involved in the protection from autoimmunity in humans.

Towards universal structure-based prediction of class II MHC epitopes for diverse allotypes

The binding of peptide fragments of antigens to class II MHC proteins is a crucial step in initiating a helper T cell immune response. The discovery of these peptide epitopes is important for understanding the normal immune response and its misregulation in autoimmunity and allergies and also for vaccine design. In spite of their biomedical importance, the high diversity of class II MHC proteins combined with the large number of possible peptide sequences make comprehensive experimental determination of epitopes for all MHC allotypes infeasible. Computational methods can address this need by predicting epitopes for a particular MHC allotype. We present a structure-based method for predicting class II epitopes that combines molecular mechanics docking of a fully flexible peptide into the MHC binding cleft followed by binding affinity prediction using a machine learning classifier trained on interaction energy components calculated from the docking solution. Although the primary advantage of structure-based prediction methods over the commonly employed sequence-based methods is their applicability to essentially any MHC allotype, this has not yet been convincingly demonstrated. In order to test the transferability of the prediction method to different MHC proteins, we trained the scoring method on binding data for DRB1*0101 and used it to make predictions for multiple MHC allotypes with distinct peptide binding specificities including representatives from the other human class II MHC loci, HLA-DP and HLA-DQ, as well as for two murine allotypes. The results showed that the prediction method was able to achieve significant discrimination between epitope and non-epitope peptides for all MHC allotypes examined, based on AUC values in the range 0.632-0.821. We also discuss how accounting for peptide binding in multiple registers to class II MHC largely explains the systematically worse performance of prediction methods for class II MHC compared with those for class I MHC based on quantitative prediction performance estimates for peptide binding to class II MHC in a fixed register.

Association ofEMCNwith Susceptibility to Rheumatoid Arthritis in a Japanese Population

Objective.

Endomucin, an endothelial-specific sialomucin, is thought to facilitate “lymphocyte homing” to synovial tissues, resulting in the major histopathologies of rheumatoid arthritis (RA). We examined the association between RA susceptibility and the gene coding endomucin,EMCN.

Methods.

Association studies were conducted with 2 DNA sample sets (initial set of 1504 patients, 752 controls; and validation set, 1113 patients, 940 controls) using 6 tag single-nucleotide polymorphisms (SNP) from the Japanese HapMap database. Immunohistochemistry for the expression of endomucin was conducted with synovial tissues from 4 patients with RA during total knee arthroplasty. Electromobility shift assays were performed for the functional study of identified polymorphisms.

Results.

Within the initial sample set, the strongest evidence of an association with RA susceptibility was SNP rs3775369 (OR 1.20, p = 0.0075). While the subsequent replication study did not initially confirm the observed significant association (OR 1.13, p = 0.062), an in-depth stratified analysis revealed significant association in patients testing positive to anti-cyclic citrullinated peptide (anti-CCP) antibody in the replication data set (OR 1.15, p = 0.044). Investigating 2 sample sets, significant associations were detected in overall and stratified samples with anti-CCP antibody status (OR 1.17, p = 0.0015). Positive staining for endomucin was detected in all patients. The allele associated with RA susceptibility had a higher binding affinity for HEK298-derived nuclear factors compared to the nonsusceptible allelic variant of rs3775369.

Conclusion.

A significant association betweenEMCNand RA susceptibility was detected in our Japanese study population. TheEMCNallele conferring RA susceptibility may also contribute to the pathogenesis of RA.

Modeling the ternary complex TCR-Vbeta/CollagenII(261-273)/HLA-DR4 associated with rheumatoid arthritis

Background

It is known that genetic predisposition to rheumatoid arthritis (RA) is associated with the MHC class II allele HLA-DR4 and that residues 261–273 of type II collagen (huCollp261) represent an immunodominant T cell epitope restricted by the DR4 molecule. Despite recent advances in characterization of MHC and T cell receptor (TCR) contacts to this epitope, the atomic details of TCR/huCollp261/HLA-DR4 ternary complex are not known.

Methodology/Principal Findings

Here we have used computational modeling to get insight into this interaction. A three-dimensional model of the TCR Vβ domain from a DR4⁺ patient affected by RA has been derived by homology modeling techniques. Subsequently, the structure of the TCR Vβ domain in complex with huCollp261/HLA-DR4 was obtained from a docking approach in conjunction with a filtering procedure based on biochemical information. The best complex from the docking experiments was then refined by 20 ns of molecular dynamics simulation in explicit water. The predicted model is consistent with available experimental data. Our results indicate that residues 97–101 of CDR3β are critical for recognition of huCollp261/HLA-DR4 by TCR. We also show that TCR contacts on p/MHC surface affect the conformation of the shared epitope expressed by DR alleles associated with RA susceptibility.

Conclusions/Significance

This work presents a three-dimensional model for the ternary complex TCR-Vβ/collagenII(261–273)/HLA-DR4 associated with rheumatoid arthritis that can provide insights into the molecular mechanisms of self reactivity.

Association of variation in Fcgamma receptor 3B gene copy number with rheumatoid arthritis in Caucasian samples

OBJECTIVE

There is increasing evidence that variation in gene copy number (CN) influences clinical phenotype. The low-affinity Fcgamma receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment to sites of inflammation and activation of polymorphonuclear neutrophils (PMNs). Given recent evidence that low FCGR3B CN is a risk factor for systemic but not organ-specific autoimmune disease and the potential importance of PMN in the pathophysiology of rheumatoid arthritis (RA), the authors hypothesised that FCGR3B gene dosage influences susceptibility to RA.

METHODS

FCGR3B CN was measured in 643 cases of RA and 461 controls from New Zealand (NZ), with follow-up analysis in 768 cases and 702 controls from the Netherlands and 250 cases and 211 controls from the UK. All subjects were of Caucasian ancestry.

RESULTS

Significant evidence for an association between CN <2 and RA was observed in the Dutch cohort (OR 2.01 (95% CI 1.37 to 2.94), p=3 x 10-4) but not in the two smaller cohorts (OR 1.45 (95% CI 0.92 to 2.26), p=0.11 and OR 1.33 (95% CI 0.58 to 3.02), p=0.50 for the NZ and UK populations, respectively). The association was evident in a meta-analysis which included a previously published Caucasian sample set (OR 1.67 (95% CI 1.28 to 2.17), p=1.2 x 10-4).

CONCLUSIONS

One possible mechanism to explain the association between reduced FCGR3B CN and RA is the reduced clearance of immune complex during inflammation. However, it is not known whether the association between RA and FCGR3B CN is aetiological or acts as a proxy marker for another biologically relevant variant. More detailed examination of genetic variation within the FCGR gene cluster is required.

The link of C4B null allele to autism and to a family history of autoimmunity in Egyptian autistic children

The reason behind the initiation of autoimmunity, which may have a role in autism, is not well understood. There is an association between some autoimmune disorders and complement (C) 4B null allele. We aimed to study the association between C4B null allele and autism. In addition, we are the first to investigate the association between this allele and a family history of autoimmune diseases in autistic children. Therefore, we examined the frequency of C4B null allele, by quantitative real-time PCR, in 80 autistic patients and 80 healthy matched-children. The frequency of C4B null allele was significantly higher in autistic patients (37.5%) than healthy controls (8.75%), P<0.001. The frequency of autoimmune diseases in families of autistic children (40%) was significantly higher than healthy children (10%), P<0.001. In addition, a family history of autoimmunity had a significant risk for association with autism (odds ratio=6, 95%, CI=2.5-14.1). C4B null allele had a significant risk for association with autism (odds ratio=6.26, 95% CI=2.55-15.36) and with a family history of autoimmunity (odds ratio=21, 95% CI=6.5-67.8).

CONCLUSIONS

the link of C4B null allele to autism and to a family history of autoimmunity may indicate its possible contributing role to autoimmunity in autism.

Lack of association of TLR4 gene Asp299Gly and Thr399Ile polymorphisms with rheumatoid arthritis in Chinese Han population of Yunnan Province

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of synovium and subsequent joint destruction. Recently, genetic polymorphisms within the toll-like receptor 4 (TLR4) genes have been reported to be associated with RA. To analyze the association between the genetic polymorphisms within TLR4 gene and the susceptibility to RA in Chinese people, two functional variants, Asp299Gly and Thr399Ile, in the TLR4 gene were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct sequencing techniques from 213 RA patients and 247 ethnically matched controls. None polymorphisms of Asp299Gly and Thr399Ile were detected in all RA cases and controls, which indicates that there is no relevance between these two SNPs and RA in the Chinese Han population. Further studies with extended single nucleotide polymorphisms (SNP) should be performed.