Peripheral Immune Dysregulation Research Articles

The potential protective role of peripheral immunophenotypes in Alzheimer's disease: a Mendelian randomization study.

Alzheimer's disease (AD) is the most widespread neurodegenerative disease in the world. Previous studies have shown that peripheral immune dysregulation plays a paramount role in AD, but whether there is a protective causal relationship between peripheral immunophenotypes and AD risk remains ambiguous. Two-sample Mendelian randomization (MR) was performed using large genome-wide association study (GWAS) genetic data to assess causal effects between peripheral immunophenotypes and AD risk. Utilizing the genetic associations of 731 immune cell traits as exposures. We adopted the inverse variance weighted method as the primary approach. The Weighted median and MR-Egger regression methods were employed as supplements. Various sensitivity analyses were performed to assess the robustness of the outcomes. Based on the IVW method, we identified 14 immune cell traits that significantly reduced the risk of AD, of which six demonstrated statistical significance in both IVW and Weighted median methods. Among the seven immune traits, four were related to regulatory T (Treg) cells : (1) CD25++ CD45RA- CD4 not regulatory T cell % T cell (odds ratio (OR) [95% confidence interval (CI)] = 0.96 [0.95, 0.98], adjusted P = 1.17E-02), (2) CD25++ CD45RA- CD4 not regulatory T cell % CD4+ T cell (OR [95% CI] = 0.97 [0.96, 0.99], adjusted P = 3.77E-02), (3) Secreting CD4 regulatory T cell % CD4 regulatory T cell (OR [95% CI] = 0.98 [0.97, 0.99], adjusted P = 7.10E-03), (4) Activated & secreting CD4 regulatory T cell % CD4 regulatory T cell(OR [95% CI] = 0.98 [0.97, 0.99], adjusted P = 7.10E-03). In addition, HLA DR++ monocyte % monocyte (OR [95% CI] = 0.93 [0.89, 0.98], adjusted P = 4.87E-02) was associated with monocytes, and HLA DR on myeloid Dendritic Cell (OR [95% CI] = 0.93 [0.89, 0.97], adjusted P = 1.17E-02) was related to dendritic cells (DCs). These findings enhance the comprehension of the protective role of peripheral immunity in AD and provide further support for Treg and monocyte as potential targets for immunotherapy in AD.

Peripheral immune function and Alzheimer's disease: a living systematic review and critical appraisal.

A growing body of literature examines the relationship between peripheral immune function and Alzheimer's Disease (AD) in human populations. Our living systematic review summarizes the characteristics and findings of these studies, appraises their quality, and formulates recommendations for future research. We searched the electronic databases PubMed, PsycINFO, and Web of Science, and reviewed references of previous reviews and meta-analyses to identify human studies examining the relationship between any peripheral immune biomarkers and AD up to September 7th, 2023. We examined patterns of reported statistical associations (positive, negative, and null) between each biomarker and AD across studies. Evidence for each biomarker was categorized into four groups based on the proportion of studies reporting different associations: corroborating a positive association with AD, a negative association, a null association, and presenting contradictory findings. A modified Newcastle-Ottawa scale (NOS) was employed to assess the quality of the included studies. In total, 286 studies were included in this review. The majority were cross-sectional (n = 245, 85.7%) and hospital-based (n = 248, 86.7%), examining relationships between 187 different peripheral immune biomarkers and AD. Cytokines were the most frequently studied group of peripheral immune biomarkers. Evidence supported a positive association with AD for six biomarkers, including IL-6, IL-1β, IFN-γ, ACT, IL-18, and IL-12, and a negative association for two biomarkers, including lymphocytes and IL-6R. Only a small proportion of included studies (n = 22, 7.7%) were deemed to be of high quality based on quality assessment. Existing research on peripheral immune function and AD exhibits substantial methodological variations and limitations, with a notable lack of longitudinal, population-based studies investigating a broad range of biomarkers with prospective AD outcomes. The extent and manner in which peripheral immune function can contribute to AD pathophysiology remain open questions. Given the biomarkers that we identified to be associated with AD, we posit that targeting peripheral immune dysregulation may present a promising intervention point to reduce the burden of AD.

Dysregulation of circulating MAIT cell subsets in patients with hidradenitis suppurativa

Abstract Hidradenitis suppurativa (HS) is a chronic inflammatory condition characterized by painful and debilitating skin lesions. Recent reports purport HS as an autoinflammatory keratinization disease with numerous pathways and features of systemic inflammation however few studies have been conducting to characterize peripheral immune dysregulation. Mucosal associated invariant T (MAIT) cells are an invariant T cell subset responding directly to bacterial threats and their dysregulation contributes to the pathogenesis of autoimmune disorders, cancers and inflammatory skin conditions. Here, we analyzed MAIT cells in the blood of 16 HS patients and 12 healthy controls (HC) by flow cytometry. We found that the frequency of MAIT cells did not change in HS patients, but their function changed drastically. We observed a significant reduction in the frequency of IFNy+ and TNFα+ MAIT cells in the periphery of HS patients. Furthermore, we analyzed MAIT cell subsets by their CD4 surface expression. Here, we found that the frequency of CD4+MAIT cells in the periphery of HS patients is significantly increased, while the frequency of CD4-MAIT cells is significantly decreased. Furthermore, HS patients have a reduction in CD4− IFNg+ and TNFa+ MAIT cells. Overall, these findings suggest that peripheral MAIT cells are dysregulated in HS patients which may contribute to the pathogenesis of the disease. NIH/NIAMS (1R21AR079089 and 1R01AR078688) for Dr. Mi and Henry Ford Immunology Program grant (T71017 for Dr. Mi and T71016 for Di Zhou).

RIPK1 mutations causing infantile-onset IBD with inflammatory and fistulizing features.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is an important regulator of necroptosis and inflammatory responses. We present the clinical features, genetic analysis and immune work-up of two patients with infantile-onset inflammatory bowel disease (IBD) resulting from RIPK1mutations. Whole exome and Sanger sequencing was performed in two IBD patients. Mass cytometry time of flight (CyTOF) was conducted for in-depth immunophenotyping on one of the patient's peripheral blood mononuclear cells, and compared to control subjects and patients with Crohn's disease. The patients presented with severe colitis and perianal fistulas in the first months of life, without severe/atypical infections. Genetic studies identified pathogenic genetic variants in RIPK1 (Patient 1, A c.1934C>T missense mutation in Exon 11; Patient 2, c.580G>A missense mutation residing in Exon 4). Protein modeling demonstrated that the mutation in Patient 1 displaces a water molecule, potentially disrupting the local environment, and the mutation in Patient 2 may lead to disruption of the packing and conformation of the kinase domain. Immunofluorescence RIPK1 staining in rectal biopsies demonstrated no expression for Patient 1 and minimal expression for Patient 2, compared to controls and patients with active Crohn's disease. Using CyTOF unbiased clustering analysis, we identified peripheral immune dysregulation in one of these patients, characterized by an increase in IFNγ CD8+T cells along with a decrease in monocytes, dendritic cells and B cells. Moreover, RIPK1-deficient patient's immune cells exhibited decreased IL-6 production in response to lipopolysaccharide (LPS) across multiple cell types including T cells, B cells and innate immune cells. Mutations inRIPK1should be considered in very young patients presenting with colitis and perianal fistulas. Given RIPK1's role in inflammasome activation, but also in epithelial cells, it is unclear whether IL1 blockade or allogeneic hematopoietic stem cell transplantation can suppress or cure the hyper-inflammatory response in these patients. Additional studies in humans are required to better define the role of RIPK1 in regulating intestinal immune responses, and how treatment can be optimized for patients with RIPK1 deficiency.

Lower lymphocyte count is associated with increased risk of Parkinson’s disease

ObjectivesPatients with established Parkinson’s disease (PD) display differences in blood biomarkers of immune function, including leukocyte differentials, compared to controls. These may be useful biomarkers to predict PD and inform pathogenesis. We sought to identify whether peripheral immune dysregulation was associated with risk of subsequent PD.MethodsWe examined the relationship between incident PD and baseline leukocyte differential count in UK Biobank, a longitudinal cohort with >500,000 participants. We used a range of sensitivity analyses and Mendelian randomization (MR) to further explore the nature of associations.ResultsAfter excluding individuals with comorbidities which could influence inflammation biomarkers, 465 incident PD cases and 312,125 controls remained. Lower lymphocyte count was associated with increased risk of PD diagnosis (per 1-SD decrease in count OR 1.18, 95% CI 1.07–1.32, padjusted=0.01). The association between lower lymphocyte count and increased PD risk remained robust to sensitivity analyses. MR suggested that the effect of lower lymphocyte count on PD risk may be causal (per 1-SD decrease in lymphocyte count; ORMR 1.09, 95% CI 1.01–1.18, p=0.02).ConclusionsWe provide converging evidence from observational analyses in UKB and MR that lower lymphocyte count is associated with an increased risk of subsequent PD.m.jensen@cantab.net

DOP64 Pathogenic RIPK1 Mutations Cause Infantile-onset IBD with Inflammatory and Fistulizing Features

Abstract Background Genetics plays a key role in the pathogenesis of inflammatory bowel disease (IBD). With the expanding use of next-generation sequencing, >70 different monogenic disorders associated with IBD have been identified, and most of them present in the first years of life. Recently, several patients with severe IBD were identified to harbor pathogenic mutations in Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) gene, which regulates necroptosis, a necrotic cell death mechanism. We present the clinical features, genetic analysis and immune work-up of three patients with infantile-onset IBD resulting from novel RIPK1 mutations. Methods Whole exome sequencing was performed in three patients with severe infantile-onset IBD, along with sanger sequencing for conformation. Mass cytometry time of flight was conducted for in-depth immunophenotyping, including cytokine secretion analysis following lipopolysaccharide (LPS) or Phorbol myristate acetate with ionomycin (PMA-I), on one of the patient’s peripheral blood mononuclear cells, and compared to control subjects and patients with Crohn’s disease. Results All patients, born to consanguineous Muslim families, presented with severe colitis and multiple perianal fistulas in the first months of life, without severe or atypical infections. One of the patients had a partial response to high doses of inlfliximab and azathioprine, while another one failed to respond to adaliumab and later to low dose anakinra, an IL-1 receptor antagonist. Genetic studies identified novel and pathogenic genetic variants in the RIPK1 gene in all patients, that were confirmed by Sanger sequencing. Using mass cytometry time of flight unbiased clustering analysis, we identified peripheral immune dysregulation in one of these patients, characterized by an increase in IFNγ CD8+ T cells along with a decrease in monocytes, dendritic cells and B cells. Moreover, RIPK1-deficient patient’s immune cells exhibited decreased IL-6 production in response to LPS across multiple cell types including T cells B cells and innate immune cells. Conclusion Mutations in RIPK1 should be considered in very young patients presenting with colitis and perianal fistulas. Given RIPK1’s role in both immune cells (and specifically in inflammasome activation), and epithelial cells, it is unclear whether immunosuppressive medications (including IL1 blockade) as well as allogeneic hematopoietic stem cell transplantation can suppress or cure the hyper-inflammatory response in these patients. Additional studies in humans are required to better define the role of RIPK1 in regulating intestinal immune responses, and how treatment can be optimized for patients with RIPK1 deficiency.

Intestinal dysbiosis promotes immune dysregulation in an animal model of Alzheimer's disease.

Current evidence suggests that systemic inflammation promotes Alzheimer's Disease (AD) and recent reports demonstrated that circulating neutrophils migrate into the AD brain inducing neuroinflammation and cognitive deficits in animal models of AD. However, how peripheral immune dysregulation occurs and promotes neuroinflammation and memory decline in AD is still unknown. Even though descriptive reports suggest the involvement of the microbiome in AD, the mechanisms behind AD pathology are not explored. In this context, we aim to better understand the dysregulation of leukocyte subpopulations in AD by addressing the gut-blood-brain axis. By taking advantage of the 3xTg-AD mouse model we addressed peripheral inflammation during early disease stages. To this aim, we performed: 1) an intestinal microbiota analysis; 2) characterization of circulating inflammatory mediators; and 3) immunophenotypization of peripheral blood. In our study we show a clear intestinal dysbiosis in the 3xTg-AD mice, characterized by higher abundance of taxa known to cause proinflammatory conditions. In agreement, we also found increased intestinal permeability and accumulation of immature precursors and aged neutrophils in circulating blood, suggesting a strong peripheral dysregulation in the early phases of the disease. Altogether, our data suggest microbiota as a modulator of leukocyte activation and migration into the brain. Therefore, targeting the gut-blood-brain axis in AD could lead to new immunomodulatory strategies for AD treatment.

Peripheral and central immune system crosstalk in Alzheimer disease - a research prospectus.

Dysregulation of the immune system is a cardinal feature of Alzheimer disease (AD), and a considerable body of evidence indicates pathological alterations in central and peripheral immune responses that change over time. Considering AD as a systemic immune process raises important questions about how communication between the peripheral and central compartments occurs and whether this crosstalk represents a therapeutic target. We established a whitepaper workgroup to delineate the current status of the field and to outline a research prospectus for advancing our understanding of peripheral–central immune crosstalk in AD. To guide the prospectus, we begin with an overview of seminal clinical observations that suggest a role for peripheral immune dysregulation and peripheral–central immune communication in AD, followed by formative animal data that provide insights into possible mechanisms for these clinical findings. We then present a roadmap that defines important next steps needed to overcome conceptual and methodological challenges, opportunities for future interdisciplinary research, and suggestions for translating promising mechanistic studies into therapeutic interventions.

Lower Lymphocyte Count is Associated With Increased Risk of Parkinson's Disease.

Objectives:Patients with established Parkinson’s disease (PD) display differences in peripheral blood markers of immune function, including leukocyte differential counts, compared with controls. These differences may be useful biomarkers to predict PD and may shed light on pathogenesis. We sought to identify whether peripheral immune dysregulation was associated with increased risk of subsequent PD diagnosis.Methods:We examined the relationship between incident PD, baseline differential leukocyte count and other blood markers of acute inflammation in UK Biobank (UKB), a longitudinal cohort with ~500,000 participants. We used a range of sensitivity analyses and Mendelian randomization (MR) to further explore the nature of associations.Results:After excluding individuals with comorbidities which could influence biomarkers of inflammation, 465 incident PD cases and 312,125 controls remained. Lower lymphocyte count was associated with increased risk of subsequent PD diagnosis (per 1-SD decrease in lymphocyte count odds ratio [OR] = 1.18, 95% confidence interval [CI] = 1.07–1.32, padjusted = 0.01). There was some evidence that reductions in eosinophil counts, monocyte counts and C-reactive protein (CRP) were associated with increased PD risk, and that higher neutrophil count was also associated. Only the association between lower lymphocyte count and increased PD risk remained robust to sensitivity analyses. MR suggested that the effect of lower lymphocyte count on PD risk may be causal (per 1-SD decrease in lymphocyte count; ORMR = 1.09, 95% CI = 1.01–1.18, p = 0.02).Interpretation:We provide converging evidence from observational analyses in UKB and MR that lower lymphocyte count is associated with an increased risk of subsequent PD.

Evaluation of Peripheral Immune Dysregulation in Alzheimer's Disease and Vascular Dementia.

Immune dysregulation has been observed in the brain and blood of patients with Alzheimer's disease (AD). However, a convenient assay to evaluate peripheral immune dysregulation in AD has not been developed, partly due to the inconsistent observations from different studies. We hypothesized that peripheral immune dysregulation may only exist in a subpopulation of AD patients; therefore it may be valuable to identify this subpopulation with a convenient assay. Along this line, we selected 14 candidate genes based on our analysis of microarray data on peripheral blood of AD and other diseases. We used RT-qPCR to examine the expression of these 14 genes in a cohort of 288 subjects, including 74 patients with AD, 64 patients with mild cognitive impairment (MCI), 51 patients with vascular dementia (VaD), and 99 elderly controls with no cognitive dysfunction/impairment. Seven of these 14 genes displayed significant difference in group comparison. Switching from group comparison to individualized evaluation revealed more in-depth information. First, there existed a wide dynamic range for the expression of these immune genes in peripheral blood even within the control group. Second, for the vast majority of the patients (AD, VaD, and MCI patients), the expression of these genes fell within the dynamic range of the control group. Third, a small portion of outliers were observed in the patient groups, more so in the VaD group than that in the AD or MCI groups. This is our first attempt to conduct personalized evaluation of peripheral immune dysregulation in AD and VaD. These findings may be applicable to the identification of peripheral immune dysregulation in AD and VaD patients which may lead to tailored treatment toward those patients.

Comparative analysis of immune cell subsets in peripheral blood from patients with periodontal disease and healthy controls.

Periodontitis is a chronic inflammatory disease caused by the colonization of teeth by the bacterial plaque biofilm and the resultant host immune responses in adjacent periodontal tissues. Disease severity can vary dramatically between patients with periodontitis, with some subjects displaying inflammation without bony destruction (gingivitis), while others experience chronic progressive or rapidly aggressive gingival connective tissue damage and bone loss. To determine whether peripheral immune dysregulation is associated with periodontitis, we performed extensive analysis of immune cell subsets in peripheral blood from patients with chronic or aggressive periodontitis versus periodontally healthy control subjects. Peripheral blood mononuclear cells (PBMC) from patients with chronic periodontitis or aggressive periodontitis and from periodontally healthy controls were analysed by 8-10-colour flow cytometry for the frequencies of various lymphocyte subsets, including interleukin (IL)-17-, interferon (IFN)-γ-, tumour necrosis factor (TNF)-α- and IL-10-producing cells, and the frequencies and phenotype of monocytes. Cytokine levels in serum from the different groups were determined by Luminex assay. We found no significant differences in the frequencies of major immune cell populations [CD4+ T cells, CD8+ T cells, γδ T cells, CD4+ CD45RO+ CD25+ CD127low regulatory T cells (Tregs ), CD19+ B cells, CD14+ monocytes] or of cytokine-producing T cells, or in the phenotype of CD14+ monocytes in peripheral blood from these patient cohorts. Additionally, no significant differences were observed in serum levels of prototypical inflammatory cytokines. These results suggest that the local gingival inflammatory response is not reflected by obvious changes in major blood immune cell subset frequencies.

Relations of combat stress and posttraumatic stress disorder to 24-h plasma and cerebrospinal fluid interleukin-6 levels and circadian rhythmicity

BackgroundAcute and chronic stress can lead to a dysregulation of the immune response. Growing evidence suggests peripheral immune dysregulation and low-grade systemic inflammation in posttraumatic stress disorder (PTSD), with numerous reports of elevated plasma interleukin-6 (IL-6) levels. However, only a few studies have assessed IL-6 levels in the cerebrospinal fluid (CSF). Most of those have used single time-point measurements, and thus cannot take circadian level variability and CSF-plasma IL-6 correlations into account. MethodsThis study used time-matched, sequential 24-h plasma and CSF measurements to investigate the effects of combat stress and PTSD on physiologic levels and biorhythmicity of IL-6 in 35 male study volunteers, divided in 3 groups: (PTSD = 12, combat controls, CC = 12, and non-deployed healthy controls, HC = 11). ResultsOur findings show no differences in diurnal mean concentrations of plasma and CSF IL-6 across the three comparison groups. However, a significantly blunted circadian rhythm of plasma IL-6 across 24 h was observed in all combat-zone deployed participants, with or without PTSD, in comparison to HC. CSF IL-6 rhythmicity was unaffected by combat deployment or PTSD. ConclusionsAlthough no significant group differences in mean IL-6 concentration in either CSF or plasma over a 24-h timeframe was observed, we provide first evidence for a disrupted peripheral IL-6 circadian rhythm as a sequel of combat deployment, with this disruption occurring in both PTSD and CC groups. The plasma IL-6 circadian blunting remains to be replicated and its cause elucidated in future research.

Molecular and Functional Neuroscience in Immunity.

The nervous system regulates immunity and inflammation. The molecular detection of pathogen fragments, cytokines, and other immune molecules by sensory neurons generates immunoregulatory responses through efferent autonomic neuron signaling. The functional organization of this neural control is based on principles of reflex regulation. Reflexes involving the vagus nerve and other nerves have been therapeutically explored in models of inflammatory and autoimmune conditions, and recently in clinical settings. The brain integrates neuro-immune communication, and brain function is altered in diseases characterized by peripheral immune dysregulation and inflammation. Here we review the anatomical and molecular basis of the neural interface with immunity, focusing on peripheral neural control of immune functions and the role of the brain in the model of the immunological homunculus. Clinical advances stemming from this knowledge within the framework of bioelectronic medicine are also briefly outlined.

Autoimmune manifestations in aged mice arise from early-life immune dysregulation

Abstract Autoantibodies that arise in autoimmunity can be present years to decades prior to the onset of disease manifestations. This suggests that the initial autoimmune trigger involves a peripheral lymphoid component, which ultimately drives disease pathology in local tissues later in life. Here we show Sjögren’s Syndrome manifestations that develop in aged NOD.H-2h4 mice were driven by and dependent on peripheral dysregulation that arose in early life. Specifically, elimination of spontaneous germinal centers that developed in spleens of young NOD.H-2h4 mice by transient blockade of CD40 ligand (CD40L) or splenectomy abolished Sjögren’s pathology of aged mice. Strikingly, a single injection of anti-CD40L at 4 weeks-of-age prevented tertiary follicle neogenesis and greatly blunted the formation of key autoantibodies implicated in glandular pathology. Microarray profiling of salivary gland characterized the expression pattern of genes that increased with disease progression and showed early anti-CD40L greatly repressed B cell function, while having a broader effect on multiple biological pathways including IL-12 and interferon signaling. Importantly, a single, prophylactic treatment with anti-CD40L also inhibited the development of autoimmune thyroiditis and diabetes in NOD.H-2h4 and NOD mice, respectively, supporting a key role for CD40L in the pathophysiology of several autoimmune models. These results suggest that early peripheral immune dysregulation gives rise to autoimmune manifestations later in life and for diseases pre-dated by autoantibodies, early prophylactic intervention with biologics may prove efficacious.

Autoimmune manifestations in aged mice arise from early-life immune dysregulation.

Autoantibodies can be present years to decades before the onset of disease manifestations in autoimmunity. This finding suggests that the initial autoimmune trigger involves a peripheral lymphoid component, which ultimately drives disease pathology in local tissues later in life. We show that Sjögren's syndrome manifestations that develop in aged NOD.H-2h4 mice were driven by and dependent on peripheral dysregulation that arose in early life. Specifically, elimination of spontaneous germinal centers in spleens of young NOD.H-2h4 mice by transient blockade of CD40 ligand (CD40L) or splenectomy abolished Sjögren's pathology of aged mice. Strikingly, a single injection of anti-CD40L at 4 weeks of age prevented tertiary follicle neogenesis and greatly blunted the formation of key autoantibodies implicated in glandular pathology, including anti-muscarinic receptor antibodies. Microarray profiling of the salivary gland characterized the expression pattern of genes that increased with disease progression and showed that early anti-CD40L greatly repressed B cell function while having a broader effect on multiple biological pathways, including interleukin-12 and interferon signaling. A single prophylactic treatment with anti-CD40L also inhibited the development of autoimmune thyroiditis and diabetes in NOD.H-2h4 and nonobese diabetic mice, respectively, supporting a key role for CD40L in the pathophysiology of several autoimmune models. These results strongly suggest that early peripheral immune dysregulation gives rise to autoimmune manifestations later in life, and for diseases predated by autoantibodies, early prophylactic intervention with biologics may prove efficacious.

Immune dysregulation and autoimmunity in bipolar disorder: Synthesis of the evidence and its clinical application

Increasing evidence suggests that inflammation and immune dysregulation play an important role in the pathogenesis of bipolar disorder. Because the brain can be affected by various autoimmune processes, it is possible that some psychiatric disorders may have an autoimmune basis. This article reviews the literature on peripheral and central immune dysregulation and autoimmunity in bipolar disorder. The mechanisms of the innate and adaptive immune systems in the pathophysiology of bipolar disorder are explored. The clinical features and pathogenesis of neuropsychiatric systemic lupus erythematosus, anti-NMDA encephalitis, and Hashimoto's encephalopathy are summarized. Neuroinflammation and peripheral immune dysregulation may play a role in the pathophysiology of bipolar disorder. This involves a complex interaction between immune cells of the central nervous system and periphery resulting in cellular damage through mechanisms involving excitotoxicity, oxidative stress, and mitochondrial dysfunction. Neuropsychiatric systemic lupus erythematosus, anti-NMDA encephalitis, and Hashimoto's encephalopathy are important differentials for a psychiatrist to consider when suspecting autoimmune encephalopathy. The link between immune dysregulation, autoimmunity, and bipolar disorder may be closer than previously thought. Psychiatrists should be vigilant for autoimmunity in presentations of bipolar disorder due to its high morbidity and therapeutic implications. Advances in neuroimaging and biomarker identification related to immune dysregulation and neuroinflammation will contribute to our knowledge of the pathophysiology of bipolar disorder.

Differential immune system DNA methylation and cytokine regulation in post‐traumatic stress disorder

DNA methylation may mediate persistent changes in gene function following chronic stress. To examine this hypothesis, we evaluated African American subjects matched by age and sex, and stratified into four groups by post-traumatic stress disorder (PTSD) diagnosis and history of child abuse. Total Life Stress (TLS) was also assessed in all subjects. We evaluated DNA extracted from peripheral blood using the HumanMethylation27 BeadChip and analyzed both global and site-specific methylation. Methylation levels were examined for association with PTSD, child abuse history, and TLS using a linear mixed model adjusted for age, sex, and chip effects. Global methylation was increased in subjects with PTSD. CpG sites in five genes (TPR, CLEC9A, APC5, ANXA2, and TLR8) were differentially methylated in subjects with PTSD. Additionally, a CpG site in NPFFR2 was associated with TLS after adjustment for multiple testing. Notably, many of these genes have been previously associated with inflammation. Given these results and reports of immune dysregulation associated with trauma history, we compared plasma cytokine levels in these subjects and found IL4, IL2, and TNFα levels associated with PTSD, child abuse, and TLS. Together, these results suggest that psychosocial stress may alter global and gene-specific DNA methylation patterns potentially associated with peripheral immune dysregulation. Our results suggest the need for further research on the role of DNA methylation in stress-related illnesses.

The Etiology of Paraneoplastic Autoimmunity

Although they may sometimes appear similar, paraneoplastic autoimmunity has a unique pathogenesis, different from the classical autoimmune diseases not associated with cancer. When distinguished clinically, paraneoplastic autoimmunity is more severe and often presents with a broader range of clinical signs and symptoms. Management of these patients is difficult and is usually centered in part on treatment of the underlying malignancy. Self-antigens recognized in the setting of paraneoplastic autoimmunity can be diverse, and the number of determinants recognized within a single antigen can be numerous. This review uses prototypic examples of paraneoplastic immune-mediated diseases and their associated malignancies to describe the mechanisms by which immune dysregulation can occur in the setting of cancer. Specific diseases covered include paraneoplastic pemphigus, Sweet's syndrome, pyoderma gangrenosum, thymoma-associated multiorgan autoimmunity, myasthenia gravis, autoimmune hemolytic anemia, immune thrombocytopenia, and the paraneoplastic neurological syndromes. The malignancies discussed include thymoma, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia, among others. The mechanisms by which cancers induce autoimmunity are broken down into the following categories: disruption of central tolerance, peripheral immune dysregulation, and alteration of self-antigens. For each category, examples of paraneoplastic autoimmune diseases and their associated malignancies are discussed. Finally, mechanisms by which cancer treatment can lead to autoimmunity and examples of polymorphisms that are linked to both cancer and autoimmunity are discussed.

TGF-β signaling is altered in the peripheral blood of subjects with multiple sclerosis

Multiple sclerosis (MS) is a central nervous system inflammatory disorder with evidence of peripheral immune dysregulation. Abnormalities of the immune suppressive cytokine TGF-β have been reported, but not fully defined, in MS. Through a pathway-focused expression profiling of the peripheral blood, we found abnormalities of TGF-βRII, SMAD4 and SMAD7 expression in subjects with MS, and reduction in the levels of TGF-β regulated genes, indicating an overall reduction in TGF-β signaling in MS. The response to exogenous TGF-β was intact, however, indicating an extrinsic defect of TGF-β signaling in MS. These results indicate that TGF-β control is diminished in MS.

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<h3>Abstract</h3> <h3>Importance</h3> Biomarkers for the early detection of Parkinson’s disease (PD) are needed. Patients with PD display differences in peripheral blood biomarkers of immune function, including leukocyte differential counts and C-reactive protein (CRP), compared to controls. These differences may be useful biomarkers to predict PD, and may shed light on PD pathogenesis. <h3>Objectives</h3> To identify whether peripheral immune dysregulation is a pre-diagnostic feature of PD, and whether it plays a causal role. <h3>Design</h3> Cross-sectional association analysis of the relationship between differential leukocyte count and other markers of acute inflammation at enrolment, and incident cases of PD in UK Biobank. We used Mendelian randomization to establish whether differences in leukocyte differential counts have a causal influence on risk of PD. <h3>Setting</h3> UK Biobank; a population-based cohort with over 500,000 participants aged 40-69 recruited in the UK between 2006 and 2010. <h3>Participants</h3> PD cases were defined as individuals with an ICD-10 coded diagnosis of PD. Cases were defined as ’incident’ if their age at diagnosis was greater than their age at recruitment to UKB. ’Controls’ were defined as individuals without a diagnosis of PD. After applying exclusion criteria for pre-existing health conditions that can influence blood counts, 507 incident PD cases and 328,280 controls were included in the analysis. <h3>Exposure</h3> Blood cell markers (absolute and relative counts) and other markers of inflammation were obtained from blood tests of participants taken at the initial visit. <h3>Results</h3> Lower lymphocyte count was associated with increased odds of incident PD (odds ratio [OR] 0.77, 95% confidence interval [CI] 0.65-0.90). There was weaker evidence of association between lower eosinophil and monocyte counts, lower CRP, and higher neutrophil counts on risk of incident PD. The association between lymphopenia and incident PD remained robust to sensitivity analyses. Mendelian randomization analyses suggested that the effect of low lymphocyte count on PD risk was causal (OR 0.91, 95% CI 0.85 - 0.99). <h3>Conclusions and relevance</h3> In this large, prospective setting, lower lymphocyte count was associated with higher risk of subsequent PD diagnosis. Furthermore genetic evidence supported a causal role for lymphocyte count on PD risk. <h3>Key points</h3> <h3>Question</h3> Is the leukcoyte differential count a feature of pre-diagnostic Parkinson’s disease? <h3>Findings</h3> In the UK Biobank, a longitudinal cohort study with over 500,000 participants, lower lymphocyte count was associated with a 23% increased odds of incident PD, a significant difference. Mendelian randomisation revealed a convincing causal effect for low lymphocyte count on PD risk. <h3>Meaning</h3> Pre-diagnostic Parkinson’s disease is associated with lower lymphocyte counts; the suggestion of causal effect may shed light on PD pathogenesis.