Current Aspects of Pathogenesis in Sjögren's Syndrome

Unlocking the genetic tapestry of autoimmune diseases: Unveiling common genes across multiple conditions

OBJECTIVES

This study aimed to unravel the complexities of autoimmune diseases by conducting a comprehensive analysis of gene expression data across 10 conditions, including systemic lupus erythematosus (SLE), psoriasis, Sjögren's syndrome, sclerosis, immune-associated diseases, osteoarthritis, cystic fibrosis, inflammatory bowel disease (IBD), type 1 diabetes, and Guillain-Barré syndrome.

METHODS

Gene expression profiles were rigorously examined to identify both upregulated and downregulated genes specific to each autoimmune disease. The study employed visual representation techniques such as heatmaps, volcano plots, and contour-MA plots to provide an intuitive understanding of the complex gene expression patterns in these conditions.

RESULTS

Distinct gene expression profiles for each autoimmune condition were uncovered, with psoriasis and osteoarthritis standing out due to a multitude of both upregulated and downregulated genes, indicating intricate molecular interplays in these disorders. Notably, common upregulated and downregulated genes were identified across various autoimmune conditions, with genes like SELENBP1, MMP9, BNC1, and COL1A1 emerging as pivotal players.

CONCLUSION

This research contributes valuable insights into the molecular signatures of autoimmune diseases, highlighting the unique gene expression patterns characterizing each condition. The identification of common genes shared among different autoimmune conditions, and their potential role in mitigating the risk of rare diseases in patients with more prevalent conditions, underscores the growing significance of genetics in healthcare and the promising future of personalized medicine.

Sialendoscopy Findings Associated with Positive Minor Salivary Gland Biopsy

OBJECTIVES

To determine the sialendoscopy findings associated with positive findings on minor salivary gland biopsy.

STUDY DESIGN

Single-center retrospective study.

METHODS

Patients ≥18 years old who underwent sialendoscopy from 2016 to 2022 and were evaluated for SS via labial minor salivary gland biopsy. Biopsy positive and negative patients were compared on the primary outcome measure of sialendoscopy findings. Data were abstracted from the sialendoscopy operative notes and included involved gland, location of ductal pathology, and the presence of scarring, stenosis, mucus plugs, webs, and dilations. Additional characteristics included demographics, presenting symptoms, caffeine or tobacco, use of drying medications, and need for additional treatments.

RESULTS

The final cohorts included 22 biopsy positive and 21 biopsy negative patients with a total of 42 glands in the biopsy positive and 37 glands in the biopsy negative groups. Biopsy positive patients were found to require dilation at the hilum and distal duct at significantly higher rates than biopsy negative patients (p < 0.0001). However, there was no statistical difference in scarring, stenosis severity, mucus, webs, or dilations between each group.

CONCLUSION

The outcomes of this study suggest that there are no distinct sialendoscopy findings associated with biopsy positive patients. The presence of significant distal stenosis on sialendoscopy may be associated with positive minor salivary biopsy. Other endoscopic parameters are likely more consistent with non-specific chronic sialadenitis.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:1183-1189, 2024.

Risk analysis of breast cancer and breast fibrocystic change in female primary Sjögren's syndrome patients

Sjögren's syndrome is an autoimmune disease with the chronic inflammation of glandular tissues, typically salivary and lacrimal glands. Since mammary tissue shares the glandular structure, Sjögren's syndrome may also target mammary tissue to cause breast diseases. We therefore determined whether primary Sjögren's syndrome (pSS) is associated with the increased risk of breast cancer (BC) and breast fibrocystic change (FC). Total 282 female patients with pSS were recruited from a medical center in Taiwan, and patients' medical records were reviewed to identify BC and ultrasonographic breast FC. The prevalence, incidence and risk factors for BC and breast FC in pSS patients were determined, and the risk factors for these breast diseases were subsequently analyzed. Our results showed that pSS patients had the increased prevalence and incidence of BC, and high anti-SSA(Ro) antibody titers were found to be associated with the increased risk of BC. Breast FC was also found highly prevalent in these patients. Comorbidity analysis as risk factor for BC in pSS patients showed diabetes mellitus was strongly associated with the increased risk of BC (odds ratio = 10.4, P = .0006), whereas breast FC was inversely associated with the risk of BC (odds ratio = 0.077 P = .0158). These data indicated that pSS is association with the increased risk of BC and with the high prevalence of ultrasonographic breast FC. Our results also suggest that, in pSS patients, the high anti-SSA(Ro) antibody titers and diabetes mellitus confer the increased risk of BC, whereas the absence of ultrasonographic breast FC predicts the higher risk of BC.

Outline of Salivary Gland Pathogenesis of Sjögren's Syndrome and Current Therapeutic Approaches

Sjögren's syndrome (SS) is an autoimmune disease characterized by the involvement of exocrine glands such as the salivary and lacrimal glands. The minor salivary glands, from which tissue samples may be obtained, are important for the diagnosis, evaluation of therapeutic efficacy, and genetic analyses of SS. In the onset of SS, autoantigens derived from the salivary glands are recognized by antigen-presenting dendritic cells, leading to the activation of T and B cells, cytokine production, autoantibody production by plasma cells, the formation of ectopic germinal centers, and the destruction of salivary gland epithelial cells. A recent therapeutic approach with immune checkpoint inhibitors for malignant tumors enhances the anti-tumor activity of cytotoxic effector T cells, but also induces SS-like autoimmune disease as an adverse event. In the treatment of xerostomia, muscarinic agonists and salivary gland duct cleansing procedure, as well as sialendoscopy, are expected to ameliorate symptoms. Clinical trials on biological therapy to attenuate the hyperresponsiveness of B cells in SS patients with systemic organ involvement have progressed. The efficacy of treatment with mesenchymal stem cells and chimeric antigen receptor T cells for SS has also been investigated. In this review, we will provide an overview of the pathogenesis of salivary gland lesions and recent trends in therapeutic approaches for SS.

Cenerimod, a selective S1P1 receptor modulator, improves organ-specific disease outcomes in animal models of Sjögren's syndrome

Background

Sjögren’s syndrome is a systemic autoimmune disease characterized by immune cells predominantly infiltrating the exocrine glands and frequently forming ectopic lymphoid structures. These structures drive a local functional immune response culminating in autoantibody production and tissue damage, associated with severe dryness of mucosal surfaces and salivary gland hypofunction. Cenerimod, a potent, selective and orally active sphingosine-1-phosphate receptor 1 modulator, inhibits the egress of lymphocytes into the circulation. Based on the mechanism of action of cenerimod, its efficacy was evaluated in two mouse models of Sjögren’s syndrome.

Methods

Cenerimod was administered in two established models of Sjögren’s syndrome; firstly, in an inducible acute viral sialadenitis model in C57BL/6 mice, and, secondly, in the spontaneous chronic sialadenitis MRL/lpr mouse model. The effects of cenerimod treatment were then evaluated by flow cytometry, immunohistochemistry, histopathology and immunoassays. Comparisons between groups were made using a Mann-Whitney test.

Results

In the viral sialadenitis model, cenerimod treatment reduced salivary gland immune infiltrates, leading to the disaggregation of ectopic lymphoid structures, reduced salivary gland inflammation and preserved organ function. In the MRL/lpr mouse model, cenerimod treatment decreased salivary gland inflammation and reduced T cells and proliferating plasma cells within salivary gland ectopic lymphoid structures, resulting in diminished disease-relevant autoantibodies within the salivary glands.

Conclusions

Taken together, these results suggest that cenerimod can reduce the overall autoimmune response and improve clinical parameters in the salivary glands in models of Sjögren’s syndrome and consequently may reduce histological and clinical parameters associated with the disease in patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02673-x.

Traditional Chinese medicine is a useful and promising alternative strategy for treatment of Sjogren's syndrome: A review

Primary Sjogren's syndrome (pSS) is a chronic autoimmune disease involving exocrine glands. Current studies have found that the occurrence of the disease is closely related to genetic, environmental and neuroendocrine factors, as well as abnormal activation of T and B lymphocytes. The etiology and pathogenesis of pSS is complex, and there is a lack of specific targeted drugs. Traditional Chinese medicines (TCMs) have been comprehensively investigated for their treatment effects on pSS. Through a systematic review of the literature, we summarized the TCMs used to treat pSS, and find that there are four major ways that TCMs are used, including upregulation of aquaporin proteins, suppression of cell apoptosis, suppression of the abnormal activation of B lymphocytes and suppression of the abnormal activation of T lymphocytes (balancing T helper type [Th]1/Th2 & Th17/Treg and suppressing follicular helper T [Tfh] cells). However, there are not enough data about the active constituents, quality control, pharmacokinetics, toxicity and modern preparations of these TCMs; therefore, more investigations are needed. This paper highlights the importance of TCMs for treating pSS and provides guidance for future investigations.

Understanding the Complexity of Sjögren's Syndrome: Remarkable Progress in Elucidating NF-κB Mechanisms

Sjögren’s syndrome (SS) is a systemic autoimmune inflammatory disease with a poorly defined aetiology, which targets exocrine glands (particularly salivary and lachrymal glands), affecting the secretory function. Patients suffering from SS exhibit persistent xerostomia and keratoconjunctivitis sicca. It is now widely acknowledged that a chronic grade of inflammation plays a central role in the initiation, progression, and development of SS. Consistent with its key role in organizing inflammatory responses, numerous recent studies have shown involvement of the transcription factor nuclear factor κ (kappa)-light-chain-enhancer of activated B cells (NF-κB) in the development of this disease. Therefore, chronic inflammation is considered as a critical factor in the disease aetiology, offering hope for the development of new drugs for treatment. The purpose of this review is to describe the current knowledge about the NF-κB-mediated molecular events implicated in the pathogenesis of SS.

Primary Juvenile Sjögren's Syndrome in a 3-Year-Old Pediatric Female Patient: Diagnostic Role of Salivary Gland Ultrasonography: Case Report

Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease affecting mainly the salivary and lacrimal glands characterized by lymphocytic infiltration which results in gland destruction and impairment of functions. SS rarely affects pediatric patients, and there are no clear diagnostic criteria as there are with adult SS. The present case reports an atypical case of SS in a 3-year-old female who was closely followed up with for 5 years. The important role of salivary gland ultrasonography (SGUS) in early diagnosis, the change in clinical picture, as well as fluctuation of serology, are noticed.

Phosphatidylinositol 3-kinase delta pathway: a novel therapeutic target for Sjögren's syndrome

Background

The phosphatidylinositol 3-kinase delta isoform (PI3Kδ) belongs to an intracellular lipid kinase family that regulate lymphocyte metabolism, survival, proliferation, apoptosis and migration and has been successfully targeted in B-cell malignancies. Primary Sjögren’s syndrome (pSS) is a chronic immune-mediated inflammatory disease characterised by exocrine gland lymphocytic infiltration and B-cell hyperactivation which results in systemic manifestations, autoantibody production and loss of glandular function. Given the central role of B cells in pSS pathogenesis, we investigated PI3Kδ pathway activation in pSS and the functional consequences of blocking PI3Kδ in a murine model of focal sialoadenitis that mimics some features of pSS.

Methods and results

Target validation assays showed significant expression of phosphorylated ribosomal protein S6 (pS6), a downstream mediator of the phosphatidylinositol 3-kinase delta (PI3Kδ) pathway, within pSS salivary glands. pS6 distribution was found to co-localise with T/B cell markers within pSS aggregates and the CD138+ plasma cells infiltrating the glands. In vivo blockade of PI3Kδ activity with seletalisib, a PI3Kδ-selective inhibitor, in a murine model of focal sialoadenitis decreased accumulation of lymphocytes and plasma cells within the glands of treated mice in the prophylactic and therapeutic regimes. Additionally, production of lymphoid chemokines and cytokines associated with ectopic lymphoneogenesis and, remarkably, saliva flow and autoantibody production, were significantly affected by treatment with seletalisib.

Conclusion

These data demonstrate activation of PI3Kδ pathway within the glands of patients with pSS and its contribution to disease pathogenesis in a model of disease, supporting the exploration of the therapeutic potential of PI3Kδ pathway inhibition in this condition.

Dysregulated Marginal Zone B Cell Compartment in a Mouse Model of Sjögren's Syndrome with Ocular Inflammation

The risk of developing lymphoma in patients with Sjögren’s syndrome (SS) is 44 times higher than in the normal population with the most common lymphomas derived from marginal zone B (MZB) cells. Current understanding of the role of MZB cells in SS is primarily based on salivary gland pathology, while their contextual association with lacrimal glands and ocular manifestations largely remains unknown. We examined this possibility using a SS mouse model (thrombospondin-1 deficient (TSP1^−/−)) with well-characterized ocular disease. We determined the frequency, localization, and cytokine profiles of MZB cells and their association with an antibody response in TSP1^−/− mice treated with a TSP-derived peptide. A significantly increased frequency of MZB cells was detected in the spleens and lacrimal glands of TSP1^−/− mice in comparison to wild-type tissues as detected by immunostaining. An altered cytokine profile of TSP1^−/− MZB cells was supportive of T helper 17 (Th17)-related pathogenesis. A significantly reduced antibody response and the splenic MZB compartment against an eye-derived antigen were noted in TSP-derived peptide-treated mice. These changes correspond with the previously reported ability of the peptide to ameliorate SS-related ocular manifestations. Collectively, our results demonstrate dysregulation of MZB cells in TSP1^−/− mice and highlight their role in the context of SS-related chronic ocular surface disease.

The role of inflammation in the development of epilepsy

Epilepsy, a neurological disease characterized by recurrent seizures, is often associated with a history of previous lesions in the nervous system. Impaired regulation of the activation and resolution of inflammatory cells and molecules in the injured neuronal tissue is a critical factor to the development of epilepsy. However, it is still unclear as to how that unbalanced regulation of inflammation contributes to epilepsy. Therefore, one of the goals in epilepsy research is to identify and elucidate the interconnected inflammatory pathways in systemic and neurological disorders that may further develop epilepsy progression. In this paper, inflammatory molecules, in neurological and systemic disorders (rheumatoid arthritis, Crohn’s, Type I Diabetes, etc.) that could contribute to epilepsy development, are reviewed.

Understanding the neurobiology of inflammation in epileptogenesis will contribute to the development of new biomarkers for better screening of patients at risk for epilepsy and new therapeutic targets for both prophylaxis and treatment of epilepsy.

Reduced myofilament component in primary Sjögren's syndrome salivary gland myoepithelial cells

Primary Sjögren's syndrome (pSS) is a solitary poorly understood autoimmune inflammatory disease by involvement of the salivary and lacrimal glands resulting in dry mouth and dry eyes. Myoepithelial cells (MECs) are cells knowing for its hybrid epithelial and mesenchymal phenotype that are important components of the salivary gland (SGs) structure aiding the expulsion of saliva from acinar lobules. In this study we investigate possible alteration in the myofilament component of MECs in SGs specimens obtained from pSS patients in comparison with healthy subjects, to evaluate MECs hypothetical involvement in the pathogenesis of pSS. The expression of alpha-smooth muscle actin (α-SMA) and p63, as MECs markers, was evaluated in bioptic specimens from pSS and healthy labial SGs through immunohistochemistry and immunofluorescence analyses; the distribution of MECs markers was quantified using Aperio ScanScope and ImageScope software to provide quantitative assessments of staining levels. Our observations demonstrated that p63 nuclear labeling in pSS MECs is preserved whereas α-SMA cytoplasmic staining is strongly and significantly reduced when compared with healthy SGs; the digital images analysis quantification of the expression of labeled α-SMA and p63 protein in the healthy and pSS MECs salivary tissues, led to results suggesting a loss of mechanical support for acini and ducts in pSS, correlated, probably, with the reduction of salivary flow that features one important aspect of pSS disease.

The potential relationship between Flammer and Sjögren syndromes: the chime of dysfunction

Flammer syndrome (FS) is a term to blanket a cluster of vascular and nonvascular signs and symptoms linked to primary vascular dysregulation (PVD), increased sensitivity to various stimuli (stress, drugs, etc.) and altered sense regulation such as pain, smell and thirst perception. On one hand, disruption of blood barrier and homeostasis of the body are the main targets of vascular irregularity. Inflammation and immune disorders including autoimmunity are considered as a consequence of the abnormal vascular regulation processes. On the other hand, decreased thirst feeling typical for FS-affected individuals may lead to extensive body dehydration resulting in dry eye appearance and breast cancer (BC) risk, amongst others. To this end, recent research demonstrated FS as linked to BC development and progression into the metastatic disease. On the other side, Sjögren syndrome (SS) is an autoimmune disease characterised by a progressive sicca syndrome associated with the dry eye symptoms, specific immunologic complex and/or significant infiltrate at minor salivary gland biopsy. SS is relatively frequent, with a clinical diagnosis predominantly amongst women. Its physiopathology is a complex battery of both environmental and genetic factors. If left untreated, SS may be associated with and/or resulted in severe arthritis and the development of B cell lymphoma. In this mini-review, we summarise the facts and hypotheses connecting FS and SS symptoms together and mechanisms potentially overlapping in both syndromes. Unraveling the common denominators between these two syndromes not only providing more evidence for interaction between altered sense regulation, vascular dysregulation, immune system dysfunction but also focusing on the individual outcomes in terms of severity grade and potential complications exploring novel diagnostic, prognostic and treatment modalities. Multi-professional considerations presented here are an example how to effectively enter the new era of preventive, predictive and personalised medicine benefiting the patients and healthcare system as the whole.

Updates on Sjögren's syndrome: from proteomics to protein biomarkers

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a complex heterogeneous autoimmune disorder, typically affecting exocrine glands. Recently, a great interest has arisen in searching for novel biomarkers able to improve the diagnostic work-up of the disease as well as the general assessment and the prognostic stratification of pSS patients. From this perspective, salivary proteomics has appeared as a promising tool considering that salivary proteins may closely reflect the underlying disease processes in the salivary glands. Areas covered: Here we will provide an update on the state of the art of proteomics in pSS, focusing in particular on putative novel biomarkers for the disease. There is a special focus on candidate salivary protein and their role in non-invasive diagnosis of pSS. Expert commentary: Proteomics represents an emerging throughput omics-based approach for use in diagnosis of pSS. The studies that have been presented in this review have provided major contributions towards the identification of putative protein biomarkers, that once validated, could be able not only to contribute to a non-invasive diagnosis of pSS but also to the stratification of different disease subsets, ultimately allowing a better comprehension of the disease.

B-cell and T-cell quantification in minor salivary glands in primary Sjögren's syndrome: development and validation of a pixel-based digital procedure

Background

Evaluating lymphocytic infiltration of minor salivary gland biopsy in primary Sjögren’s syndrome is challenging. We developed and evaluated a digital method for quantifying B and T lymphocytes in whole minor salivary gland biopsy slides.

Methods

Minor salivary gland biopsies were immunostained with anti-CD20/anti-CD3 antibodies using red/brown chromogens. Slides were digitised and spliced into mosaics of smaller JPEG format images in which red and brown pixels were counted. ImageJ Cell counter was used for validation. Agreement between the digital and manual methods was evaluated using Bland-Altman plots and the interclass correlation coefficient. External validation relied on the Chisholm-Mason, Tarpley, and focus-score methods.

Results

Of 62 minor salivary gland biopsy slides, 61.3 % had a Chisholm-Mason grade ≥ III or a focus score ≥1. The number of pixels correlated well with manual cell counts (r = 0.95 for red pixels vs. B cell count and r = 0.91 for brown pixels vs. T cell count). Interclass correlation coefficients between digital and manual counts were excellent (0.92 for B/T cells). B-cell proportion showed a significant positive correlation with the focus score (Spearman’s coefficient 0.463, p < 0.0001). Median B-cell proportion was lower in minor salivary gland biopsies with Chisholm grades I–II (2.5 % (0.2–13.9)) than III–IV (30.0 % (15.5–45.2)) and increased with Tarpley’s class (1, 2.2 % (0.2–6.6); 2, 27.2 % (13.0–38.9); and 3–4, 48.5 % (29.4–56.4); p < 0.001 for all comparisons). Minor salivary gland biopsy B-cell proportion was also significantly correlated with several markers of clinical and biological activity of the disease, especially with markers of systemic B-cell hyperactivation.

Conclusion

The digital procedure proved accurate compared to the reference standard, producing reliable results for whole tissue sections.

Trial registration

ClinicalTrials.gov [NCT00740948]. Registered 22 August 2008.

Increase of Intracellular BAFF in B Cells of Sjögren's Patients Is Not Affected by Decrease of BAFFR

The presence of a broad spectrum of autoantibodies in Sjögren's syndrome (SjS) patients is the result of abnormal B-cell regulation that can be at least partially explained by abnormal BAFF/BAFFR regulation. The objective of this study was to determine both membrane and intracellular expression of BAFF/BAFFR in monocytes and B-cells in peripheral blood of 19 primary Sjögren's syndrome patients and 20 healthy controls using flow cytometry. We also measured sBAFF in serum. Compared to healthy controls, both surface and intracellular expression of BAFF was significantly increased in monocytes and B-cells of SjS patients. Also serum sBAFF level was elevated. Expression of BAFFR on B-cells of SjS patients was surprisingly decreased, but there was no clear increase or decrease within monocytes. Our results indicate that activated monocytes communicate with B-cells via BAFF and BAFFR, so that B-cells are stimulated, but BAFF is also produced to stimulate cells in autocrine way. The decrease of BAFFR expression in SjS patients suggests that there is the mechanism that attempts to take over in order to balance the high level of BAFF.

New treatments for inflammatory rheumatic disease

As our understanding of the pathogenesis of autoimmune diseases is growing, new therapies are being developed to target disease-specific pathways. Since the introduction of etanercept in 1998, several biotechnological agents have been developed, most of them indicated in the treatment of rheumatoid arthritis, but also psoriatic arthritis. Most currently available molecules target TNF-alfa with different strategies (i.e., etanercept, infliximab, adalimumab, golimumab, and certolizumab pegol), IL-6 (tocilizumab), CTLA-4 (abatacept), and B cells (rituximab, belimumab) as they are key mediators in the cascade of inflammation. Further, small molecules have been recently developed to target intracellular signaling, such as Janus Kinases for tofacitinib, the first FDA-approved small molecule for rheumatoid arthritis. Most novel treatments are being developed for arthritis with specific differences between rheumatoid and psoriatic arthritis, as well as for systemic lupus erythematosus, following the approval of belimumab. Finally, biologic therapies are effective also in gout, mainly targeting interleukin-1 to block the inflammasome. This review article describes the new and upcoming treatment options for rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, and gout to dissect what we should be aware of when discussing these new and promising molecules.

B-cell survival factors in autoimmune rheumatic disorders

Autoimmune rheumatic disorders have complex etiopathogenetic mechanisms in which B cells play a central role. The importance of factors stimulating B cells, notably the B-cell activating factor (BAFF) and A proliferation inducing ligand (APRIL) axis is now recognized. BAFF and APRIL are cytokines essential for B-cell proliferation and survival from the immature stages to the development of plasma cells. Their levels are increased in some subsets of patients with autoimmune disorders. Several recent biologic drugs have been developed to block this axis, namely belimumab [already licensed for systemic lupus erythematosus (SLE) treatment], tabalumab, atacicept and blisibimod. Many clinical trials to evaluate the safety and efficacy of these drugs in several autoimmune disorders are ongoing, or have been completed recently. This review updates the information on the use of biologic agents blocking BAFF/APRIL for patients with SLE, rheumatoid arthritis, Sjögren's syndrome and myositis.

Central pathways causing fatigue in neuro-inflammatory and autoimmune illnesses

BACKGROUND

The genesis of severe fatigue and disability in people following acute pathogen invasion involves the activation of Toll-like receptors followed by the upregulation of proinflammatory cytokines and the activation of microglia and astrocytes. Many patients suffering from neuroinflammatory and autoimmune diseases, such as multiple sclerosis, Parkinson's disease and systemic lupus erythematosus, also commonly suffer from severe disabling fatigue. Such patients also present with chronic peripheral immune activation and systemic inflammation in the guise of elevated proinflammtory cytokines, oxidative stress and activated Toll-like receptors. This is also true of many patients presenting with severe, apparently idiopathic, fatigue accompanied by profound levels of physical and cognitive disability often afforded the non-specific diagnosis of chronic fatigue syndrome.

DISCUSSION

Multiple lines of evidence demonstrate a positive association between the degree of peripheral immune activation, inflammation and oxidative stress, gray matter atrophy, glucose hypometabolism and cerebral hypoperfusion in illness, such as multiple sclerosis, Parkinson's disease and chronic fatigue syndrome. Most, if not all, of these abnormalities can be explained by a reduction in the numbers and function of astrocytes secondary to peripheral immune activation and inflammation. This is also true of the widespread mitochondrial dysfunction seen in otherwise normal tissue in neuroinflammatory, neurodegenerative and autoimmune diseases and in many patients with disabling, apparently idiopathic, fatigue. Given the strong association between peripheral immune activation and neuroinflammation with the genesis of fatigue the latter group of patients should be examined using FLAIR magnetic resonance imaging (MRI) and tested for the presence of peripheral immune activation.

SUMMARY

It is concluded that peripheral inflammation and immune activation, together with the subsequent activation of glial cells and mitochondrial damage, likely account for the severe levels of intractable fatigue and disability seen in many patients with neuroimmune and autoimmune diseases.This would also appear to be the case for many patients afforded a diagnosis of Chronic Fatigue Syndrome.