Updated assessment of the prevalence, spectrum and case definition of autoimmune disease

Myasthenia Gravis: paradox versus paradigm in autoimmunity

Myasthenia Gravis (MG) is a paradigm of organ-specific autoimmune disease (AID). It is mediated by antibodies that target the neuromuscular junction. The purpose of this review is to place MG in the general context of autoimmunity, to summarize the common mechanisms between MG and other AIDs, and to describe the specific mechanisms of MG. We have chosen the most common organ-specific AIDs to compare with MG: type 1 diabetes mellitus (T1DM), autoimmune thyroid diseases (AITD), multiple sclerosis (MS), some systemic AIDs (systemic lupus erythematous (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS)), as well as inflammatory diseases of the gut and liver (celiac disease (CeD), Crohn's disease (CD), and primary biliary cirrhosis (PBC)). Several features are similar between all AIDs, suggesting that common pathogenic mechanisms lead to their development. In this review, we address the predisposing factors (genetic, epigenetic, hormones, vitamin D, microbiota), the triggering components (infections, drugs) and their interactions with the immune system [1,2]. The dysregulation of the immune system is detailed and includes the role of B cells, Treg cells, Th17 and cytokines. We particularly focused on the role of TNF-α and interferon type I whose role in MG is very analogous to that in several other AIDS. The implication of AIRE, a key factor in central tolerance is also discussed. Finally, if MG is a prototype of AIDS, it has a clear specificity compared to the other AIDS, by the fact that the target organ, the muscle, is not the site of immune infiltration and B cell expansion, but exclusively that of antibody-mediated pathogenic mechanisms. By contrast, the thymus in the early onset subtype frequently undergoes tissue remodeling, resulting in the development of ectopic germinal centers surrounded by high endothelial venules (HEV), as observed in the target organs of many other AIDs.

Gene-environment interaction in autoimmune disease

Autoimmune disease manifests in numerous forms, but as a disease group is relatively common in the population. It is complex in aetiology, with genetic and environmental determinants. The involvement of gene variants in autoimmune disease is well established, and evidence for significant involvement of the environment in various disease forms is growing. These factors may act independently, or they may interact, with the effect of one factor influenced by the presence of another. Identifying combinations of genetic and environmental factors that interact in autoimmune disease has the capacity to more fully explain disease risk profile, and to uncover underlying molecular mechanisms contributing to disease pathogenesis. In turn, such knowledge is likely to contribute significantly to the development of personalised medicine, and targeted preventative approaches. In this review, we consider the current evidence for gene-environment (G-E) interaction in autoimmune disease. Large-scale G-E interaction research efforts, while well-justified, face significant practical and methodological challenges. However, it is clear from the evidence that has already been generated that knowledge on how genes and environment interact at a biological level will be crucial in fully understanding the processes that manifest as autoimmunity.

Discovery of biomarkers for systemic lupus erythematosus using a library of synthetic autoantigen surrogates

Antibodies to a wide range of self-antigens, including those directed against nucleic acids or nucleic acid-binding proteins are the essential biomarkers for diseases such as systemic lupus erythematosus (SLE). Highly complex libraries of nonamers consisting of N-substituted glycines (peptoids) were screened for compounds that bound IgG from patients with SLE and earlier, incomplete autoimmune syndromes. Peptoids were identified that could identify subjects with SLE and related syndromes with a high sensitivity (70%) and specificity (97.5%). Immobilized peptoids were used to isolate IgG from both healthy subjects and SLE patients that reacted with known RNA-binding proteins. In the case of SLE patients, the peptoid-purified IgG reacted with several autoantigens, suggesting that the peptoids are capable of interacting with multiple, structurally similar molecules. These results show that the measurement of IgG binding to peptoids can identify subjects with high levels of pathogenic autoantibodies.

Genes and functional GI disorders: from casual to causal relationship

BACKGROUND

The functional gastrointestinal disorders (FGID), and in particular irritable bowel syndrome (IBS), pose a considerable burden on health care and society, and negatively impact quality of life. These are common conditions of unknown etiology, and symptom-based criteria are currently the sole nosological tools for their clinical classification. Major insight into FGID pathophysiology is therefore needed and, in recent years, increasing hope has been put on genetic research for the identification of causative pathways. This is more advanced in IBS compared with other FGID, but it has still provided often indecipherable results and no unequivocal evidence of a pathogenetic role for any particular gene. Although thousands of genetic variants have been undoubtedly linked to human disease in hundreds of genome-wide association studies (GWAS), no similar effort has yet even been attempted in FGID. If meaningful, robust, and reproducible results are to be obtained for IBS and other FGID, we must shift gear and adopt these powerful hypothesis-free approaches through concerted actions and allocation of adequate resources. Provided these are in place, the major challenge will be, inevitably, the choice of the target phenotype(s) beyond a descriptive symptom-based classification.

PURPOSE

In view of these much awaited developments, salient results and difficulties inherent to IBS gene discovery are briefly summarized here.

The "missing link" in autoimmunity and autism: extracellular mitochondrial components secreted from activated live mast cells

Autoimmune diseases continue to increase, but the reason(s) remain obscure and infections have not proven to be major contributors. Mast cells are tissue immune cells responsible for allergies, but have been increasingly shown to be involved in innate and acquired immunity, as well as inflammation. This involvement is possible because of their ability to release multiple mediators in response to a great variety of triggers. We recently published that activation of mast cells is accompanied by mitochondrial fission and translocation to the cell surface from where they secrete at least ATP and DNA outside the cell without cell damage. These extracellular mitochondrial components are misconstrued by the body as "innate pathogens" leading to powerful autocrine and paracrine auto-immune/auto-inflammatory responses. We also showed that mitochondrial DNA is increased in the serum of young children with autism spectrum disorders (ASD), a condition that could involve "focal brain allergy/encephalitits". Blocking the secretion of extracellular mitochondrial components could present unique possibilities for the therapy of ASD and other autoimmune diseases. Unique formulation of the flavonoid luteolin offers unique advantages.

Innate and adaptive immunity in inflammatory bowel disease

Inflammatory bowel disease (IBD) includes Crohn's disease (CD) and ulcerative colitis (UC). The exact cause of IBD remains unknown. Available evidence suggests that an abnormal immune response against the microorganisms of the intestinal flora is responsible for the disease in genetically susceptible individuals. The adaptive immune response has classically been considered to play a major role in the pathogenesis of IBD. However, recent advances in immunology and genetics have clarified that the innate immune response is equally as important in inducing gut inflammation in these patients. In particular, an altered epithelial barrier function contributes to intestinal inflammation in patients with UC, while aberrant innate immune responses, such as antimicrobial peptide production, innate microbial sensing and autophagy are particularly associated to CD pathogenesis. On the other hand, besides T helper cell type (Th)1 and Th2 immune responses, other subsets of T cells, namely Th17 and regulatory T (Treg) cells, are likely to play a role in IBD. However, given the complexity and probably the redundancy of pathways leading to IBD lesions, and the fact that Th17 cells may also have protective functions, neutralization of IL-17A failed to induce any improvement in CD. Studying the interactions between various constituents of the innate and adaptive immune systems will certainly open new horizons in the knowledge about the immunologic mechanisms implicated in gut inflammation.

Autoantibody profiling in multiple sclerosis using arrays of human protein fragments

Profiling the autoantibody repertoire with large antigen collections is emerging as a powerful tool for the identification of biomarkers for autoimmune diseases. Here, a systematic and undirected approach was taken to screen for profiles of IgG in human plasma from 90 individuals with multiple sclerosis related diagnoses. Reactivity pattern of 11,520 protein fragments (representing ∼38% of all human protein encoding genes) were generated on planar protein microarrays built within the Human Protein Atlas. For more than 2,000 antigens IgG reactivity was observed, among which 64% were found only in single individuals. We used reactivity distributions among multiple sclerosis subgroups to select 384 antigens, which were then re-evaluated on planar microarrays, corroborated with suspension bead arrays in a larger cohort (n = 376) and confirmed for specificity in inhibition assays. Among the heterogeneous pattern within and across multiple sclerosis subtypes, differences in recognition frequencies were found for 51 antigens, which were enriched for proteins of transcriptional regulation. In conclusion, using protein fragments and complementary high-throughput protein array platforms facilitated an alternative route to discovery and verification of potentially disease-associated autoimmunity signatures, that are now proposed as additional antigens for large-scale validation studies across multiple sclerosis biobanks.

Longitudinal observational study of sporadic inclusion body myositis: implications for clinical trials

Sporadic inclusion body myositis (IBM) is the most common acquired myopathy occurring in adults aged over 50 years. The aim of the study was to assess prospectively the clinical features and functional impact of sporadic inclusion body myositis (IBM). Clinical data, manual muscle testing (MMT), quantitative muscle testing (QMT) of quadriceps muscle and IBM functional rating scale (IBM-FRS) were collected according to a standardised protocol at baseline (n=51) and one-year follow-up (n=23). MMT, quadriceps QMT and IBM-FRS significantly declined after one year (by 5.2%, 27.9%, and 13.8%, respectively). QMT of the quadriceps muscle and IBM-FRS were the most sensitive measures of disease progression. After a median time of seven years of disease duration, 63% of patients had lost independent walking. Disease onset after 55 years of age, but not sex or treatment, is predictive of a shorter time to requirement of a walking stick. We detected no differences in disease presentation and progression between clinically and pathologically defined IBM patients. The study provides evidence that quadriceps QMT and IBM-FRS could prove helpful as outcome measures in future therapeutic trials in IBM.

Common variable immunodeficiency: crossroads between infections, inflammation and autoimmunity

Common variable immunodeficiency is a collection of diseases characterized by primary hypogammaglobulinemia. The causes of CVID are extremely heterogeneous and may affect virtually every pathway linked to B cell development and function. Clinical manifestations of CVID mainly include recurrent bacterial infections, but autoimmune, gastrointestinal, lymphoproliferative, granulomatous, and malignant disorders have also been frequently reported as associated conditions. We aimed to focus on the state of the art of the relationship between infections, inflammation and autoimmunity in CVID.