Twin studies in auto-immune disease

Metabolites: deciphering the molecular language between DCs and their environment

Dendritic cells (DCs) determine the outcome of the immune response based on signals they receive from the environment. Presentation of antigen under various contexts can lead to activation and differentiation of T cells for immunity or dampening of immune responses by establishing tolerance, primarily through the priming of regulatory T cells. Infections, inflammation and normal cellular interactions shape DC responses through direct contact or via cytokine signaling. Although it is widely accepted that DCs sense microbial components through pattern recognition receptors (PRRs), increasing evidence advocates for the existence of a set of signals that can profoundly shape DC function via PRR-independent pathways. This diverse group of host- or commensal-derived metabolites represents a newly appreciated code from which DCs can interpret environmental cues. In this review, we discuss the existing information on the effect of some of the most studied metabolites on DC function, together with the implications this may have in immune-mediated diseases.

Coherent somatic mutation in autoimmune disease

BACKGROUND

Many aspects of autoimmune disease are not well understood, including the specificities of autoimmune targets, and patterns of co-morbidity and cross-heritability across diseases. Prior work has provided evidence that somatic mutation caused by gene conversion and deletion at segmentally duplicated loci is relevant to several diseases. Simple tandem repeat (STR) sequence is highly mutable, both somatically and in the germ-line, and somatic STR mutations are observed under inflammation.

RESULTS

Protein-coding genes spanning STRs having markers of mutability, including germ-line variability, high total length, repeat count and/or repeat similarity, are evaluated in the context of autoimmunity. For the initiation of autoimmune disease, antigens whose autoantibodies are the first observed in a disease, termed primary autoantigens, are informative. Three primary autoantigens, thyroid peroxidase (TPO), phogrin (PTPRN2) and filaggrin (FLG), include STRs that are among the eleven longest STRs spanned by protein-coding genes. This association of primary autoantigens with long STR sequence is highly significant (p<3.0x10(-7)). Long STRs occur within twenty genes that are associated with sixteen common autoimmune diseases and atherosclerosis. The repeat within the TTC34 gene is an outlier in terms of length and a link with systemic lupus erythematosus is proposed.

CONCLUSIONS

The results support the hypothesis that many autoimmune diseases are triggered by immune responses to proteins whose DNA sequence mutates somatically in a coherent, consistent fashion. Other autoimmune diseases may be caused by coherent somatic mutations in immune cells. The coherent somatic mutation hypothesis has the potential to be a comprehensive explanation for the initiation of many autoimmune diseases.

Autoimmunity and environment: am I at risk?

The complex interplay between environmental factors and genetic susceptibility plays an essential role in disease pathogenesis. This is especially true for autoimmunity, where clinical reports, genomic and epidemiological studies, as well as animal models have identified several environmental and genetic risk factors associated with autoimmune disease. The complexity of this relationship is demonstrated by the vast array of environmental factors that have now been implicated in the induction, and possibly the maintenance of autoimmune disease. The multitude of environmental factors implicated includes both infectious and non-infectious agents. Here, we review one specific autoimmune disease, primary biliary cirrhosis (PBC), as a model for environmental risk factors acting in concert with genetic susceptibility in the disease pathogenesis. PBC is an ideal model, as both infectious and non-infectious environmental agents have been identified as risk factors, and their study provides clues for unravelling the pathogenesis of the disease.

Epstein-barr virus as a trigger of autoimmune liver diseases

The pathogenesis of autoimmune diseases includes a combination of genetic factors and environmental exposures including infectious agents. Infectious triggers are commonly indicated as being involved in the induction of autoimmune disease, with Epstein-Barr virus (EBV) being implicated in several autoimmune disorders. EBV is appealing in the pathogenesis of autoimmune disease, due to its high prevalence worldwide, its persistency throughout life in the host's B lymphocytes, and its ability to alter the host's immune response and to inhibit apoptosis. However, the evidence in support of EBV in the pathogenesis varies among diseases. Autoimmune liver diseases (AiLDs), including autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC), have a potential causative link with EBV. The data surrounding EBV and AiLD are scarce. The lack of evidence surrounding EBV in AiLD may also be reflective of the rarity of these conditions. EBV infection has also been linked to other autoimmune conditions, which are often found to be concomitant with AiLD. This paper will critically examine the literature surrounding the link between EBV infection and AiLD development. The current evidence is far from being conclusive of the theory of a link between EBV and AiLD.

Hair dyes as a risk for autoimmunity: from systemic lupus erythematosus to primary biliary cirrhosis

Environmental and genetic factors appear to be involved in the pathogenesis of primary biliary cirrhosis (PBC), a chronic cholestatic liver disease characterized by immune-mediated destruction of the small and medium sized intrahepatic bile ducts. Environmental factors include exposure to various infectious, xenobiotic and chemical compounds. These exposures may occur occupationally, through water or air contamination, pharmacological administration or by elective exposure, to name a few. Hair dyes are compounds that have been implicated in the development of several autoimmune diseases, including systemic lupus erythematosus (SLE) and PBC. So far, only epidemiological studies have addressed the role of hair dyes in PBC, with limited results. Hair dyes in SLE have been examined, and have recently demonstrated an association, both epidemiologically and immunologically. This follows a series of negative studies, which may not have taken into account several features of hair dye use. This review will examine the literature surrounding hair dye use and SLE, and compare this to data surrounding PBC. Treating physicians should be prepared for questions surrounding the need to take precautions against repeated hair dye use and this topic is discussed further.

Acute myeloid leukemia developing in patients with autoimmune diseases

Therapy-related acute myeloid leukemia is an unfortunate complication of cancer treatment, particularly for patients with highly curable primary malignancies and favorable life expectancy. The risk of developing therapy-related acute myeloid leukemia also applies to patients with non-malignant conditions, such as autoimmune diseases treated with cytotoxic and/or immunosuppressive agents. There is considerable evidence to suggest that there is an increased occurrence of hematologic malignancies in patients with autoimmune diseases compared to the general population, with a further increase in risk after exposure to cytotoxic therapies. Unfortunately, studies have failed to reveal a clear correlation between leukemia development and exposure to individual agents used for the treatment of autoimmune diseases. Given the dismal outcome of secondary acute myeloid leukemia and the wide range of available agents for treatment of autoimmune diseases, an increased awareness of this risk and further investigation into the pathogenetic mechanisms of acute leukemia in autoimmune disease patients are warranted. This article will review the data available on the development of acute myeloid leukemia in patients with autoimmune diseases. Possible leukemogeneic mechanisms in these patients, as well as evidence supporting the association of their primary immunosuppressive status and their exposure to specific therapies, will also be reviewed. This review also supports the idea that it may be misleading to label leukemias that develop in patients with autoimmune diseases who are exposed to cytotoxic agents as 'therapy-related leukemias'. A better understanding of the molecular defects in autoimmune disease patients who develop acute leukemia will lead to a better understanding of the association between these two diseases entities.

Environmental agents and autoimmune diseases

Autoimmune diseases, which comprise over 80 clinically distinct conditions, are characterized by the presence of autoantibodies or autoreactive T cells directed against self structures (autoantigens). While these often incurable disorders appear to be rapidly increasing in recognition throughout the world, their rarity, heterogeneity and complex etiologies have limited our understanding of their pathogeneses. The precise mechanisms for the development of autoimmune diseases are not known, however, evidence from many complementary lines of investigation suggests that autoimmune diseases result from the interactions of both environmental and genetic risk factors. While considerable progress has been made in understanding multiple genetic risk factors for many autoimmune diseases, relatively little information is now available regarding the role of the environment in the development of these illnesses. This chapter examines the limited but growing evidence for the role of the environment in the development and progression of autoimmune diseases, the specific exposures that have been suspected of being involved, the possible mechanisms by which these agents may induce and sustain autoimmune processes and the approaches needed to better understand these issues in the future. Identifying the necessary and sufficient genetic and environmental risk factors for disease holds the promise of allowing for the prevention of some illnesses through avoidance of environmental risk factors by genetically susceptible individuals or via gene or other therapies to correct the effects of deleterious genetic risk factors in the case of unavoidable environmental agents.

High incidence of autoantibodies in Fabry disease patients

Fabry disease (FD) is an X-linked disorder of glycosphingolipid catabolism that results from a deficiency of the lysosomal enzyme alpha-galactosidase A. This defect leads to the accumulation of its substrates, mainly globotriaosylceramide, in lysosomes of cells of different tissues. Different studies have shown the involvement of immunopathologies in different sphingolipidoses. The coexistence of FD and immune disorders such as systemic lupus erythematosus, rheumatoid arthritis and IgA nephropathy, has been described in the literature. The aim of this study was to evaluate the prevalence of a group of autoantibodies in a series of Argentine FD patients. Autoantibodies against extractable nuclear antigens (ENAs), double-stranded DNA, anticardiolipin and phosphatidylserine were assayed by ELISA. Lupus anticoagulants were also tested. Fifty-seven per cent of the samples showed reactivity with at least one autoantigen. Such reactivities were more frequent among males than among females. Antiphospholipid autoantibodies were detected in 45% of our patients. The high rate of thrombosis associated with FD could be related, at least in part, to the presence of antiphospholipid autoantibodies in Fabry patients. We found the presence of ENAs, which are a characteristic finding of rheumatological diseases, previous a frequent misdiagnosis of FD, in around 39% of the cases. The detection of a high level of autoantibodies must be correlated clinically to determine the existence of an underlying autoimmune disease. With the recent development of therapy, the life expectancy in FD will increase and autoimmune diseases might play an important role in the morbidity of FD.

Chaotic solar cycles modulate the incidence and severity of mental illness

This paper hypothesizes that the intensity of ultraviolet radiation (UVR) from the Sun predisposes humans to polygenic mutation fostering major mental illness (MMI) and other disorders of neurodevelopment. In addition, the variation in the intensity of this radiation acts to stress immune systems, possibly mediated by cytokines, resulting in variable clinical expressions of mental illness and autoimmune disorders. Organisms can adapt to chronic high-intensity UVR by producing melanin and by retaining various pigments. We found that 28% of 11-year solar cycles produce particularly severe solar flares during which UVR is 300% more intense and hence more damaging than normal. Out of a total of six severe cycles in the past 250 years, four have occurred in the past 55 years, possibly explaining the apparent increase in the incidence of MMI in recent decades. UVR is 10 times more mutagenic than ionizing radiation to nuclear DNA, and especially damaging to mitochondrial DNA. However, variable light as manifested by seasons stresses adaptability to UVR, possibly through an immune mechanism. We show that the region of the Earth having the most UVR, relative to the most variation in that light, is at 54 +/-10 degrees (N or S) latitude. Therefore, the most potential damage from sunlight occurs between the Equator and the Poles, not at the Equator itself. The human brain, our most important organ of adaptability, must be able to survive environmental variation, with successful matching to the environment resulting in adaptation. Unsuccessful adaptation to UVR (and possibly other types of radiation) results in mutation, which can produce neuro-chemical abnormalities manifested by MMI. We postulate that the combination of intensity and variation in UVR serves as a global modulator of MMI.

Pattern of hypocretin (orexin) soma and axon loss, and gliosis, in human narcolepsy

Human narcolepsy is correlated with a greatly reduced number of hypocretin (orexin) containing neurons and axons, and an elevated level of hypothalamic gliosis. We now report that the percentage loss of Hcrt cells and percentage elevation of GFAP staining are variable across forebrain and brain-stem nuclei, and are maximal in the posterior and tuberomammillary hypothalamic region. Regional gliosis and percent loss of hypocretin axons in narcoleptics are not correlated with regional hypocretin cell soma density in normals or with regional percent soma loss in narcoleptics. Rather they are independently and strongly correlated with the regional density of hypocretin axons and the message density for hypocretin receptor 2, as quantified in the rat. These results are consistent with the hypotheses that the loss of hypocretin function in narcolepsy results from a cytotoxic or immunologically mediated attack focused on hypocretin receptor 2 or an antigen anatomically linked to hypocretin receptor 2, and that this process is intensified in regions of high axonal density.

Type 1 diabetes and prediabetic state in a monozygotic triplet

Type 1 diabetes mellitus (IDDM) results from a chronic process of autoimmune destruction of beta cells of the Langerhans islets. The presence of autoantibodies (ICA, GADA, anti-IA2, IAA) in serum precedes the clinical onset of the disease. Genetic predisposition for IDDM is connected with HLA, CTLA-4 and insulin gene region. The aim of the study was the genetic and immunological analysis of a triplet. One of them developed Type 1 diabetes mellitus. We analysed HLA class II, CTLA-4 and insulin gene polymorphisms in the whole family. Besides, we investigated immunological status of three brothers. All patients present identical genotype for VNTR loci: D1S80, D17S5 and Apo B, as well as for HLA-DRB1, -DQA1, -DQB1, CTLA-4 gene and all studied insulin gene polymorphisms. That proves their monozigosity. The triplet presents strong genetic predisposition for IDDM. The two patients without overt diabetes have increased levels of ICA, GADA, IA2 and IAA.

Autoimmune disease in first-degree relatives of patients with multiple sclerosis. A UK survey

Previous studies examining an association with other autoimmune diseases have suggested the existence of a generalized autoimmune diathesis in patients with multiple sclerosis. We investigated the prevalence of autoimmune disease in first-degree relatives of probands with multiple sclerosis using a case-control method. The results show an excess of autoimmune disease within these families, but no significant association was seen with non-autoimmune diseases. The higher risk in multiplex than simplex families suggests an effect of genetic loading. While the increase in risk applies to each autoimmune disease, autoimmune thyroid disease (and Graves' disease in particular) contributes disproportionately to the excess risk. There was no increase in autoimmune disease within patients with multiple sclerosis themselves when compared with the index controls or population data. We conclude that autoimmune disease is more common in first-degree relatives of patients with multiple sclerosis and hypothesize that common genetic susceptibility factors for autoimmunity co-exist with additional disease specific genetic or environmental factors, which determine clinical phenotype in the individual.

Familial vs sporadic rheumatoid arthritis (RA). A prospective study in an early RA inception cohort

OBJECTIVES

To study potential differences in demographic, process and outcome variables between familial and sporadic rheumatoid arthritis (RA) in an early RA inception cohort.

METHODS

In 1998, we ascertained the familial status of all collaborative patients in a large early RA inception cohort at our department. Familial RA was defined by the presence of at least two siblings fulfilling the American College of Rheumatology criteria for RA. Baseline demographic data and prospectively recorded disease activity variables, therapies and radiological damage during the first 6 yr of disease were included in the analysis. A regression analysis was performed to assess whether familial clustering is a prognostic factor.

RESULTS

We identified 142 patients with sporadic and 36 with familial RA. The most striking difference between these groups was the larger sibship size in multicase families (8.2 +/- 2.5 vs 5. 5 +/- 2.8; P < 0.0001). Age at onset was similar in both groups, although males with familiar RA were younger at disease onset than those with sporadic RA (median 50 vs 57 yr; P=0.03). No differences were found in gender, presence of rheumatoid factor (RF), antinuclear factor and HLA-DR typing or in disease activity, interventions and outcome over 6 yr of follow-up. Early radiological damage and disease activity, but not familial history of RA were prognostic for X-ray damage.

CONCLUSION

We show that sibship size is the only relevant risk factor for familial RA. No differences in genotypic and phenotypic characteristics, disease severity or radiological damage were observed among familial and sporadic RA. Familial history of RA is not a poor prognostic factor. This prospective study confirms previous cross-sectional findings in the Dutch population.

In vivo survival of viral antigen-specific T cells that induce experimental autoimmune encephalomyelitis

A peptide derived from the human papillomavirus L2 protein is recognized by a myelin basic protein (MBP)-specific T cell clone from a multiple sclerosis patient and by MBP-specific autoantibodies purified from multiple sclerosis brain tissue. We now show in mice that low doses of this papillomavirus peptide were optimal in selecting a subpopulation of papillomavirus peptide-specific T cells that cross-reacted with MBP(87-99) and with an unrelated viral peptide derived from the BSLF1 protein of Epstein-Barr virus (EBV). These low dose viral peptide- specific T cell lines were highly encephalitogenic. Splenocytes from mice transferred with viral peptide-specific T cells showed a vigorous response to both the papillomavirus and MBP peptides, indicating that viral antigen-specific T cells survived for a prolonged time in vivo. The EBV peptide, unable to prime and select an autoreactive T cell population, could still activate the low dose papillomavirus peptide-specific cells and induce central nervous system (CNS) autoimmunity. Cytokine profiles of papillomavirus peptide-specific encephalitogenic T cells and histopathology of CNS lesions resembled those induced by MBP. These results demonstrate conserved aspects in the recognition of the self-antigen and a cross-reactive viral peptide by human and murine MBP-specific T cell receptors. We demonstrate that a viral antigen, depending on its nature, dose, and number of exposures, may select autoantigen-specific T cells that survive in vivo and can trigger autoimmune disease after adoptive transfer.

What is the evidence of genetic factors in the etiology of Graves' disease? A brief review

Graves' disease (GD) is generally thought of as a multifactorial disorder in which genetic susceptibility interacts with environmental and endogenous factors to cause disease. The importance of genetic factors is suggested by the clustering of GD within families and by a higher concordance rate for disease in monozygotic than dizygotic twins. This has, however, recently been shown to be less pronounced than previously thought. During the last decade, much effort has been put into characterization of the genetic background of GD. Until recently most studies have examined associations between GD and the human leukocyte antigen (HLA) region, but recent advances in molecular techniques have opened the way for whole-genome screening. A number of HLA and non-HLA candidate genes have been proposed, but despite several large investigations within multiplex families no major susceptibility genes have been identified. This brief review discusses relevant articles published from 1940 through 1997 regarding the influence of genetic factors in the etiology of GD. Ongoing studies will focus on whole genome screening in multiplex families as well as population based twin studies. However, the possibility of GD being a heterogeneous disease without a single well-defined genotype and phenotype should be left open.

What is the evidence of genetic factors in the etiology of Graves' disease? A brief review

Graves' disease (GD) is generally thought of as a multifactorial disorder in which genetic susceptibility interacts with environmental and endogenous factors to cause disease. The importance of genetic factors is suggested by the clustering of GD within families and by a higher concordance rate for disease in monozygotic than in dizygotic twins. This has, however, recently been shown to be less pronounced than previously thought. During the last decade much effort has been put into characterization of the genetic background of GD. Until recently, most studies have examined associations between GD and the human leukocyte antigen (HLA) region, but recent advances in molecular techniques have opened the way for whole genome screening. A number of HLA and non-HLA candidate genes have been proposed, but despite several large investigations within multiplex families no major susceptibility genes have been identified. This brief review discusses relevant articles published from 1940 through 1997 regarding the influence of genetic factors in the etiology of GD. Ongoing studies focus on whole genome screening in multiplex families as well as population-based twin studies. However, the possibility of GD being a heterogeneous disease without a single well-defined genotype and phenotype should be left open.