IgM predominance in autoimmune disease: Genetics and gender

Sequential carbonyl derivatives and hydrazone adduct formation on myeloperoxidase contribute to development of ANCA vasculitis

Drug-induced autoimmune diseases are increasingly recognized, although mechanistic insight into disease causation is lacking. Hydralazine exposure has been linked to autoimmune diseases, including antineutrophil cytoplasmic autoantibody (ANCA) vasculitis. Our hypothesis posits that hydralazine covalently binds to myeloperoxidase (MPO), triggering the autoimmune response in ANCA vasculitis. In vitro, we observed formation of carbonyl derivatives on amine groups in the presence of acrolein. This facilitated the subsequent binding of hydralazine to heme-containing proteins, including MPO, via a Michael addition. Our studies demonstrated that carbonyl derivatives and hydrazone adducts induced conformational changes in the MPO heavy chain, potentially changing its immunogenicity. We identified hydrazone adducts on circulating MPO in patients with hydralazine-associated ANCA vasculitis. These patients exhibited elevated anti-MPO IgM levels, while anti-MPO IgG levels were comparable between hydralazine-associated and nonhydralazine-associated vasculitis patients. IgM isolated from patients with hydralazine-associated MPO ANCA demonstrated a heightened affinity to hydralazine-modified MPO and activated neutrophil-like HL-60 cells. Hydralazine-modified MPO was pathogenic, as demonstrated by splenocyte transfer in a mouse model of ANCA vasculitis. Our findings unveil a mechanism of drug-induced autoimmunity wherein stepwise chemical modifications of MPO lead to conformational changes and hydrazone adduct formation, producing a neoantigen that generates pathogenic autoantibodies.

Emerging strategies for nanomedicine in autoimmunity

Autoimmune disorders have risen to be among the most prevalent chronic diseases across the globe, affecting approximately 5-7% of the population. As autoimmune diseases steadily rise in prevalence, so do the number of potential therapeutic strategies to combat them. In recent years, fundamental research investigating autoimmune pathologies has led to the emergence of several cellular targets that provide new therapeutic opportunities. However, key challenges persist in terms of accessing and specifically combating the dysregulated, self-reactive cells while avoiding systemic immune suppression and other off-target effects. Fortunately, the continued advancement of nanomedicines may provide strategies to address these challenges and bring innovative autoimmunity therapies to the clinic. Through precise engineering and rational design, nanomedicines can possess a variety of physicochemical properties, surface modifications, and cargoes, allowing for specific targeting of therapeutics to pathological cell and organ types. These advances in nanomedicine have been demonstrated in cancer therapies and have the broad potential to advance applications in autoimmunity therapies as well. In this review, we focus on leveraging the power of nanomedicine for prevalent autoimmune disorders throughout the body. We expand on three key areas for the development of autoimmunity therapies - avoiding systemic immunosuppression, balancing interactions with the immune system, and elevating current platforms for delivering complex cargoes - and emphasize how nanomedicine-based strategies can overcome these barriers and enable the development of next-generation, clinically relevant autoimmunity therapies.

Laboratory risk factors for coexistent primary biliary cholangitis in patients with Sjögren's syndrome: a retrospective study

BACKGROUND

Limited research exists on the laboratory characteristics of coexistent primary biliary cholangitis (PBC) and Sjögren's syndrome (SS). This study aimed to investigate the laboratory risk factors for the coexistence of PBC in patients with SS.

METHODS

Eighty-two patients with coexistent SS and PBC (median age 52.50 years) and 82 age- and sex-matched SS controls were retrospectively enrolled between July 2015 and July 2021. The clinical and laboratory characteristics of the two groups were compared. Laboratory risk factors for the coexistence of PBC in patients with SS were analyzed using logistic regression analysis.

RESULTS

Both groups had a similar prevalence of hypertension, diabetes, thyroid disease, and interstitial lung disease. Compared with the SS group, patients in the SS + PBC group had higher levels of liver enzymes, immunoglobulins M (IgM), G2, and G3 (P < 0.05). The percentage of patients with an antinuclear antibody (ANA) titre > 1:10000 in the SS + PBC group was 56.1%, higher than that in the SS group (19.5%, P < 0.05). Additionally, cytoplasmic, centromeric, and nuclear membranous patterns of ANA and positive anti-centromere antibody (ACA) were observed more frequently in the SS + PBC group (P < 0.05). Logistic regression analysis showed that elevated IgM levels, high ANA titre, cytoplasmic pattern, and ACA were independent risk factors for PBC coexistence in SS.

CONCLUSIONS

In addition to established risk factors, elevated IgM levels, positive ACA, and high ANA titre with cytoplasmic pattern provide clues to clinicians for the early screening and diagnosis of PBC in patients with SS.

Single-cell RNA sequencing of peripheral blood reveals immune cell dysfunction in premature ovarian insufficiency

Background

Premature ovarian insufficiency (POI) is one of the most common causes of female infertility and the etiology is highly heterogeneous. Most cases are idiopathic and the pathogenesis remains unclear. Previous studies proved that the immune system plays a crucial role in POI. However, the precise role of immune system remains unclear. This study aimed to analyze the characteristics of peripheral blood mononuclear cells (PBMC) from patients with POI by single-cell RNA sequencing (scRNA-seq) and to explore the potential involvement of immune response in idiopathic POI.

Methods

PBMC was collected from three normal subjects and three patients with POI. PBMC was subjected to scRNA-seq to identify cell clusters and differently expressed genes (DEGs). Enrichment analysis and cell-cell communication analysis were performed to explore the most active biological function in the immune cells of patients with POI.

Results

In total, 22 cell clusters and 10 cell types were identified in the two groups. Compared with normal subjects, the percentage of classical monocytes and NK cells was decreased, the abundance of plasma B cells was increased, and CD4/CD8 ratio was significantly higher in POI. Furthermore, upregulation of IGKC, IFITM1, CD69, JUND and downregulation of LYZ, GNLY, VCAN, and S100A9 were identified, which were enriched in NK cell-mediated cytotoxicity, antigen processing and presentation, and IL-17 signaling pathway. Among them, IGHM and LYZ were respectively the most significantly upregulated and downregulated genes among all cell clusters of POI. The strength of cell-cell communication differed between the healthy subjects and patients with POI, and multiple signaling pathways were assessed. The TNF pathway was found to be unique in POI with classical monocytes being the major target and source of TNF signaling.

Conclusions

Dysfunction of cellular immunity is related to idiopathic POI. Monocytes, NK cells, and B cells, and their enriched differential genes may play a role in the development of idiopathic POI. These findings provide novel mechanistic insight for understanding the pathogenesis of POI.

Characterization and Clinical Association of Autoantibodies Against Perilipin 1 in Patients With Acquired Generalized Lipodystrophy

Acquired generalized lipodystrophy (AGL) is a rare condition characterized by massive loss of adipose tissue through the body, causing severe metabolic complications. Autoimmune destruction of adipocytes is strongly suspected based on the frequent association of AGL with autoimmune disorders. In 2018, autoantibodies against perilipin 1 (PLIN1) were identified in three patients with autoimmune-associated AGL. However, the pathogenic mechanism and clinical impact of anti-PLIN1 remain unsolved. The prevalence of anti-PLIN1 autoantibodies in an AGL cohort of 40 patients was 50% (20 of 40). Among positive patients, 10 had the autoimmune variety and 10 had panniculitis-associated AGL. The IgG isotype was predominant, although some IgM antibodies were detected. Epitope-mapping studies did not identify a single, major epitope. Instead, autoantibodies typically bound to several different peptides, among which the central (233-405) domain was detected in all antibody-positive patients, for both IgG and IgM autoantibodies. In-depth epitope mapping indicated that anti-PLIN1 autoantibodies predominantly recognize the αβ-hydrolase domain containing 5 (ABHD5) binding site (383-405). Autoantibodies dose-dependently blocked the binding of PLIN1 to ABHD5 and caused a dislocation of ABHD5 toward the cytosol, leading to an increase in lipolysis and lipase activities. Finally, anti-PLIN1 titers significantly correlated with the amount of fat loss, metabolic control impairment, and severity of liver injury. Our data strongly support that anti-PLIN1 autoantibodies are a diagnostic biomarker and a cause of lipodystrophy in patients with AGL.

An indirect approach for reference intervals establishment of immunoglobulin A, G and M: the combination of laboratory database and statistics

Immunoglobulins are affected by sex, age and region, so it is necessary to establish suitable reference intervals (RIs) for clinical diagnosis. Various statistical methods were used to calculate RIs, but there has been a lack of comparison among the methods. Research based on immunoglobulin RIs establishment with various methods would provide a methodological basis for further research. A total of 16,525 individuals were enrolled in the study. Individuals were selected in the medical examination center of First Hospital of Jilin University from 2014 to 2020. The lambda-mu-sigma (LMS) method was performed to evaluate the dynamic changes in analytes. RIs were calculated by parametric, non-parametric, Hoffman method and Bhattacharya method. Sex and age partitions were found for immunoglobulins G and immunoglobulin M. The levels of IgM showed no difference with age in males, but showed differences after 50 years of age in females. Circulating immunoglobulin A concentrations showed an increasing trend with age, and immunoglobulin M showed a fluctuating trend with age. Obvious difference (>5%) was commonly found among the four methods, however, the RIs established by the four methods all passed the verification with a high passing rate. Sex and age differences should be considered for immunoglobulins G and immunoglobulin M in clinical practice. The feasibility of the four indirect methods was proven, which would provides a methodological reference for further studies and benefit the application of clinical data.

Pulmonary Manifestations of Primary Humoral Deficiencies

Primary immunodeficiencies are a group of conditions characterized by developmental or functional alterations in the immune system caused by hereditary genetic defects. Primary immunodeficiencies may affect either the innate or the adaptive (humoral and cellular) immune system. Pulmonary complications in primary humoral deficiencies are frequent and varied and are associated with high morbidity and mortality rates. The types of complications include bronchiectasis secondary to recurrent respiratory infections and interstitial pulmonary involvement, which can be associated with autoimmune cytopenias, lymphoproliferation, and a range of immunological manifestations. Early detection is key to timely management. Immunoglobulin replacement therapy reduces the severity of disease, the frequency of exacerbations, and hospital admissions in some primary humoral deficiencies. Therefore, the presence of pulmonary disease with concomitant infectious and/or autoimmune complications should raise suspicion of primary humoral deficiencies and warrants a request for immunoglobulin determination in blood. Once diagnosis is confirmed; early immunoglobulin replacement therapy will improve the course of the disease. Further studies are needed to better understand the pathogenesis of pulmonary disease related to primary humoral deficiencies and favor the development of targeted therapies that improve the prognosis of patients.

Factors associated with IgG levels in adults with IgG subclass deficiency

Background

Factors associated with IgG levels in adults with IgG subclass deficiency (IgGSD) are incompletely understood. We studied adults with IgGSD with subnormal IgG1 only, subnormal IgG1/IgG3, or subnormal IgG3 only without other subnormal IgG subclasses, IgA, or IgM. We compiled: age; sex; autoimmune condition(s) (AC); atopy; IgG, IgG subclasses, IgA, IgM; IgGsum (IgG1 + IgG2 + IgG3 + IgG4); and D (percentage difference between IgGsum and IgG). We compared attributes of patients with/without subnormal IgG (< 7.00 g/L; subnormal IgG1 subclass groups only) and analyzed IgGsum and IgG relationships. We performed backward stepwise regressions on IgG using independent variables IgG subclasses, age, and sex and on D using independent variables age and sex.

Results

There were 39 patients with subnormal IgG1 only (89.7% women), 53 with subnormal IgG1/IgG3 (88.7% women), and 115 with subnormal IgG3 only (91.3% women). Fifteen patients (38.5%) and 32 patients (60.4%) in the respective subnormal IgG1 subclass groups had subnormal IgG. Attributes of patients with/without IgG < 7.00 g/L were similar, except that AC prevalence was lower in patients with subnormal IgG1 only and IgG < 7.00 g/L than ≥ 7.00 g/L (p = 0.0484). Mean/median IgG1 and IgG2 were significantly lower in patients with IgG < 7.00 g/L in both subnormal IgG1 subclass groups (p < 0.0001, all comparisons). Regressions on IgG in three subclass groups revealed positive associations with IgG1 and IgG2 (p < 0.0001 each association). Regressions on D revealed no significant association. IgG1 percentages of IgGsum were lower and IgG2 percentages were higher in patients with subnormal IgG1 subclass levels than subnormal IgG3 only (p < 0.0001 all comparisons).

Conclusions

We conclude that both IgG1 and IgG2 are major determinants of IgG in patients with subnormal IgG1, combined subnormal IgG1/IgG3, or subnormal IgG3 and that in patients with subnormal IgG1 or combined subnormal IgG1/IgG3, median IgG2 levels are significantly lower in those with IgG < 7.00 g/L than those with IgG ≥ 7.00 g/L.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00447-3.

Factors associated with serum IgM concentrations: a general adult population study

BACKGROUND AND AIM

To investigate the influence of common factors on serum immunoglobulin M (IgM) concentrations in adults, and clinical associations with high and low values.

METHODS

We measured serum IgM levels using immunonephelometry in a random sample of 1510 individuals (aged 18-91 years, 44.7% male). We obtained data defining metabolic syndrome from all participants, defined atopy by skin prick tests to aeroallergens, and assessed lifestyle factors by questionnaire.

RESULTS

Women showed higher IgM concentrations than men; 95 (6.3%, mostly male) individuals showed low (<0.40 g/L) IgM values, and 64 (4.2%, mostly female) showed high (>2.30 g/L) IgM values. Individuals with abnormal IgM concentrations had no history of opportunistic infections nor a different atopy prevalence. Serum IgM concentrations decreased with age, and obesity was negatively associated with IgM concentrations. Alcohol consumption, smoking, physical activity, and metabolic syndrome had no significant influence in the multivariate analyses.

CONCLUSIONS

Many adults in the general population show abnormally high or low IgM concentrations with no evidence of immunodeficiency-associated diseases. Sex and age should be considered when defining reference IgM concentrations.

Clinical, Immunological, and Functional Characterization of Six Patients with Very High IgM Levels

Very high IgM levels represent the hallmark of hyper IgM (HIGM) syndromes, a group of primary immunodeficiencies (PIDs) characterized by susceptibility to infections and malignancies. Other PIDs not fulfilling the diagnostic criteria for HIGM syndromes can also be characterized by high IgM levels and susceptibility to malignancies. The aim of this study is to characterize clinical phenotype, immune impairment, and pathogenic mechanism in six patients with very high IgM levels in whom classical HIGM syndromes were ruled out. The immunological analysis included extended B-cell immunophenotyping, evaluation of class switch recombination and somatic hypermutation, and next generation sequencing (NGS). Recurrent or severe infections and chronic lung changes at the diagnosis were reported in five out of six and two out of six patients, respectively. Five out of six patients showed signs of lymphoproliferation and four patients developed malignancies. Four patients showed impaired B-cell homeostasis. Class switch recombination was functional in vivo in all patients. NGS revealed, in one case, a pathogenic mutation in PIK3R1. In a second case, the ITPKB gene, implicated in B- and T-cell development, survival, and activity was identified as a potential candidate gene. Independent of the genetic basis, very high IgM levels represent a risk factor for the development of recurrent infections leading to chronic lung changes, lymphoproliferation, and high risk of malignancies.

A Review of the Impact of Neuter Status on Expression of Inherited Conditions in Dogs

Gonadectomy is an important reproductive management tool employed in many countries, and is highly prevalent in the US with an estimated 85% of dogs being neutered. Despite the societal benefits in pet population control, negative associations between neuter status, and health conditions have been reported in recent years. Most particularly observed are the consequences of early age neutering. Knowing that different physiological systems rely upon gonadal steroids during development and physiological maintenance, studies have been undertaken to assess the impact of neuter status on multiple body and organ systems. For some inherited conditions, neutering is associated with an increased risk of expression. Neutering has also been associated with altered metabolism and a predisposition for weight gain in dogs, which may confound the detected risk association between neutering and disease expression. This review summarizes the effects of neutering on cancer, orthopedic, and immune disorders in the dog and also explores the potentially exacerbating factor of body weight.

Predicting Severe Infection and Effects of Hypogammaglobulinemia During Therapy With Rituximab in Rheumatic and Musculoskeletal Diseases

OBJECTIVE

To evaluate predictors of serious infection events (SIEs) during rituximab (RTX) therapy and effects of hypogammaglobulinemia on SIE rates, and humoral response and its persistence after discontinuation of RTX in the treatment of rheumatic and musculoskeletal diseases (RMDs).

METHODS

A retrospective longitudinal study of 700 RMD patients treated with RTX in a single center was conducted. Immunoglobulin levels were measured at baseline and at 4-6 months after each treatment cycle. Baseline predictors of SIEs were assessed using multivariable logistic regression; for RTX cycles 2-4, a mixed-effects logistic regression model was used.

RESULTS

A total of 507 patients (72%) had rheumatoid arthritis, 94 (13%) had systemic lupus erythematosus, 49 (7%) had antineutrophil cytoplasmic antibody-associated vasculitis, and 50 (7%) had other RMDs. The number of SIEs recorded was 281 in 176 patients (9.8 per 100 person-years). Predictors of SIEs included non-RTX-specific comorbidities (previous history of SIE, cancer, chronic lung disease, diabetes mellitus, and heart failure), higher corticosteroid dose, and RTX-specific factors, including low IgG (<6 gm/liter) both at baseline and during treatment, RTX-associated neutropenia, higher IgM, and longer time to RTX re-treatment, but not B cell count or depletion status. Of 110 patients with low IgG, SIE rates were higher in those with low IgG at baseline (16.4 per 100 person-years) and in those who acquired low IgG during or after RTX treatment (21.3 per 100 person-years) versus those with normal IgG (9.7 per 100 person-years). Five of 8 patients (63%) had impaired humoral response to pneumococcus and hemophilus following vaccination challenge, and only 4 of 11 patients (36%) had IgG normalized after switching biologic disease-modifying antirheumatic drugs.

CONCLUSION

Immunoglobulin levels should be monitored at baseline and before each RTX cycle to identify patients at risk of SIEs. Individualized risk-benefit assessment should be undertaken in those with lower IgG as this is a consistent SIE predictor and may increase infection profiles when RTX is switched to different therapies.

Remarkable improvement in progressive multifocal leukoencephalopathy following acute pyelonephritis with bacteremia

Progressive multifocal leukoencephalopathy (PML) is caused by John Cunningham (JC) virus in immunocompromized patients such as those with human immunodeficiency virus (HIV) infection, hematological malignancy, autoimmune disorder, and immunodeficiency disorder as well as those undergoing chemotherapy or immunosuppressive therapy. No effective treatments have been established for PML, which commonly causes severe neurological sequelae. We describe the first case of PML in a patient without HIV infection who exhibited remarkable improvement following acute pyelonephritis with Escherichia coli bacteremia.

The Sjögren's syndrome-associated autoantigen Ro52/TRIM21 modulates follicular B cell homeostasis and immunoglobulin production

Systemic rheumatic diseases are characterized by abnormal B cell activation with autoantibody production and hypergammaglobulinaemia. Ro52/SSA, also denoted tripartite motif (TRIM)21, is a major autoantigen in Sjögren's syndrome and systemic lupus erythematosus. Interestingly, TRIM21-deficient mice develop systemic autoimmunity with B cell-driven manifestations such as autoantibodies, hypergammaglobulinaemia and glomerulonephritis following tissue injury. The mechanisms by which TRIM21-deficiency leads to enhanced B cell activation and antibody production are, however, not well understood, and to further elucidate the role of TRIM21 in systemic autoimmunity, we investigated the B cell phenotype and antibody responses of Trim21^-/- mice following immunization with thymus-dependent (TD) and thymus-independent (TI) antigens. We found that TRIM21-deficient mice developed significantly higher specific antibody titres than their wild-type counterparts upon B cell receptor (BCR) engagement by TD and TI type II antigens, and this was accompanied by an altered B cell phenotype. Furthermore, BCR cross-linking, but not anti-CD40 stimulation, in vitro resulted in a significantly higher proliferation of Trim21^-/- cells. We also observed that splenic follicular B cells were expanded not only in immunized mice but also already in young, unmanipulated Trim21^-/- mice, and transcriptomic analysis of these cells revealed an up-regulation of genes associated with B cell differentiation, indicating a role for TRIM21 in their regulation. In conclusion, in this study we describe a link between the rheumatic autoantigen Ro52/TRIM21 and increased antibody production associated with follicular B cell expansion, implicating a potential role for Ro52/TRIM21 in the pathogenesis of systemic autoimmune diseases.

Comprehensive review of autoantibodies in patients with hyper-IgM syndrome

Hyper-immunoglobulin M syndrome is an X-linked primary immunodeficiency disease caused by mutations in the CD40 ligand gene. The CD40 ligand has been recently highlighted as playing a key role in the pathogenesis of primary biliary cholangitis. In the present study, we assessed an extensive set of serum autoantibodies in a series of well-defined patients with hyper-immunoglobulin M syndrome. Serum, liver-related and liver-not-related autoantibodies IgG, IgM and IgA were tested by ELISA and standard indirect immunofluorescence in HEp-2 cells in 13 Tunisian patients (8 males and 5 females, aged 1-12 years) with hyper-immunoglobulin M syndrome during 1995-2012 and, as controls, 21 age- and gender-matched blood donors. The level of IgM antibody against MIT3 was significantly higher in patients than in controls (35.8 vs 10.7, P=0.002). Half of the hyperimmunoglobulin M syndrome patients were found to be anti-MIT3 IgM positive vs none of the controls (P<0.0001). Twenty-three percent of patients were found to be anti-sp100 antibody positive vs only 0.05% of controls. By immunofluorescence, 92.3% of patients were MIT3 IgM positive vs none of the controls. In conclusion, the IgM class of anti-MIT3 antibodies was shown to be present by both ELISA and immunofluorescence in most of the patients with hyper-immunoglobulin M syndrome. The presence of the hallmark of primary biliary cholangitis, a disease where the CD40 ligand is a key player, in an immunodeficiency disease caused by mutations in the CD40 ligand gene is very intriguing and opens new scenarios in understanding the immune pathogenesis of primary biliary cholangitis.

Increased level of B cell differentiation factor in systemic lupus erythematosus patients

Most autoimmune disease are driven by a dysfunction in T and B cells, but B cells are still an interesting area of research, perturbations in their development are implicated in autoimmune diseases. B cell differentiating factor (BCDF) plays a part in the differentiation of B cells. The aim was To assess the levels of BCDF, IgM and IgG in SLE patients and whether they have any peculiarity in the clinical context of SLE. Thirty six patients with SLE and 24 healthy volunteers as control were enrolled in the study. BCDF was measured using Sandwich ELISA, total human IgM and IgG were measured by calorimetric methods. The mean concentrations of BCDF and IgM were significantly higher in patients with SLE as compared with controls (P < 0.001 and P < 0.0001 respectively). No significant difference was observed as regard IgG. We observed positive correlation between BCDF and IgM (r = 0.281, P = 0.03), and between IgG and IgM, duration of the disease (r = 0.468, P = 0.004, r = 0.337, P = 0.008 respectively). Moreover we observed lower IgM level in patients with discoid lesion (P = 0.009) and lower IgG level in those with hematologic manifestations (P = 0.02). ROC analysis revealed area under curve (AUC) 0.861 for BCDF and 0.902 for IgM, they can delineate SLE from controls at a cut-off value of 98.5 pg/ml, and 18 mg/dl IgM respectively.

Conclusion

BCDF and IgM are increased in SLE patients and are promissing diagnostic markers for SLE.

Natural regulatory IgM-mediated autoimmune responses directed against malondialdehyde regulate oxidative and nitrosative pathways and coupled with IgM responses to nitroso adducts attenuate depressive and physiosomatic symptoms at the end of term pregnancy

AIM

We aimed to delineate the effects of immunoglobulin (Ig)M-mediated autoimmune responses directed against malondialdehyde (MDA) and nitroso (SNO) adducts on nitro-oxidative stress and depressive and physiosomatic symptoms (DPSS) at the end of term.

METHODS

IgM responses to MDA, NO (nitroso) adducts formed by nitrosylation, and NO₂ tyrosine formed by nitration were measured as well as hydroperoxides (ferrous oxidation xylenol orange), advanced protein oxidation products (AOPP), and NO metabolite (NOx) levels in women at the end of term pregnancy and in normal controls.

RESULTS

IgM responses to MDA were significantly and inversely associated with AOPP, ferrous oxidation xylenol orange, and NOx and DPSS. IgM responses to NO adducts were significantly and inversely associated with DPSS and positively with NOx levels. There were significant associations between IgM responses to MDA, NO adducts, and NO₂ tyrosine. The DPSS score was predicted by AOPP and a lifetime history of premenstrual syndrome (both positively) and IgM responses to NO adducts (inversely). Furthermore, 71.8% of the variance in the index of nitro-oxidative stress was explained by lowered IgM responses to MDA, antioxidant levels (zinc, total radical trapping parameter), and inflammatory mediators.

CONCLUSION

Lowered levels of IgM responses to MDA during pregnancy are accompanied by a reduced regulation of nitro-oxidative processes thereby explaining increased oxidative and nitrosative stress biomarkers in association with DPSS. IgM responses to NO adducts, which reflect nitrosylation as a consequence of increased NO production, regulate DPSS symptoms at the end of term and are a trait marker of major depression. IgM responses to MDA are a key part of the compensatory anti-inflammatory responses system.

Clinical Phenotypes of Hyper-IgM Syndromes

The primary immunodeficiency (PID) diseases comprise a heterogeneous group of inherited disorders of immune function. Technical advancements in whole-genome, whole-exome, and RNA-sequencing have seen the explosion of genetic discoveries in the field of PIDs. The present review aims to focus on a group of immunodeficiency disorders associated with elevated levels of IgM (hyper IgM; HIGM) and provides a clinical differential diagnosis. Most patients present for evaluation of immunodeficiency due to recurrent infections, and laboratory studies show either a clear isolated elevation of serum immunoglobulin M (IgM) with low or absent IgG, IgA, and IgE. Alternatively, IgM levels may be normal or moderately elevated while other serum immunoglobulins are reported below the norms for age but not absent. Mechanistically, these disorders are recognized as defects in immunoglobulin (Ig) class switch recombination (CSR). Importantly, to safeguard genetic stability, CSR utilizes elements of the DNA repair machinery including multi-protein complexes involved in mismatch repair (MMR). Therefore, it is not uncommon for defects in the DNA repair machinery, to present with laboratory findings of HIGM. This review will discuss clinical phenotypes associated with congenital defects associated with HIGM. Clinical manifestations, relevant immunologic testing, inheritance pattern, molecular diagnosis, presumed pathogenesis, and OMIM number, when annotated are compiled. Accepted therapeutic options, when available, are reviewed for each condition discussed.

Human Plasma N-glycosylation as Analyzed by Matrix-Assisted Laser Desorption/Ionization-Fourier Transform Ion Cyclotron Resonance-MS Associates with Markers of Inflammation and Metabolic Health

Glycosylation is an abundant co- and post-translational protein modification of importance to protein processing and activity. Although not template-defined, glycosylation does reflect the biological state of an organism and is a high-potential biomarker for disease and patient stratification. However, to interpret a complex but informative sample like the total plasma N-glycome, it is important to establish its baseline association with plasma protein levels and systemic processes. Thus far, large-scale studies (n >200) of the total plasma N-glycome have been performed with methods of chromatographic and electrophoretic separation, which, although being informative, are limited in resolving the structural complexity of plasma N-glycans. MS has the opportunity to contribute additional information on, among others, antennarity, sialylation, and the identity of high-mannose type species.Here, we have used matrix-assisted laser desorption/ionization (MALDI)-Fourier transform ion cyclotron resonance (FTICR)-MS to study the total plasma N-glycome of 2144 healthy middle-aged individuals from the Leiden Longevity Study, to allow association analysis with markers of metabolic health and inflammation. To achieve this, N-glycans were enzymatically released from their protein backbones, labeled at the reducing end with 2-aminobenzoic acid, and following purification analyzed by negative ion mode intermediate pressure MALDI-FTICR-MS. In doing so, we achieved the relative quantification of 61 glycan compositions, ranging from Hex₄HexNAc₂ to Hex₇HexNAc₆dHex₁Neu5Ac₄, as well as that of 39 glycosylation traits derived thereof. Next to confirming known associations of glycosylation with age and sex by MALDI-FTICR-MS, we report novel associations with C-reactive protein (CRP), interleukin 6 (IL-6), body mass index (BMI), leptin, adiponectin, HDL cholesterol, triglycerides (TG), insulin, gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), and smoking. Overall, the bisection, galactosylation, and sialylation of diantennary species, the sialylation of tetraantennary species, and the size of high-mannose species proved to be important plasma characteristics associated with inflammation and metabolic health.

Lung Disease in Primary Antibody Deficiencies

Primary antibody deficiencies (PADs) are the most common form of primary immunodeficiency and predispose to severe and recurrent pulmonary infections, which can result in chronic lung disease including bronchiectasis. Chronic lung disease is among the most common complications of PAD and a significant source of morbidity and mortality for these patients. However, the development of lung disease in PAD may not be solely the result of recurrent bacterial infection or a consequence of bronchiectasis. Recent characterization of monogenic immune dysregulation disorders and more extensive study of common variable immunodeficiency have demonstrated that interstitial lung disease (ILD) in PAD can result from generalized immune dysregulation and frequently occurs in the absence of pneumonia history or bronchiectasis. This distinction between bronchiectasis and ILD has important consequences in the evaluation and management of lung disease in PAD. For example, treatment of ILD in PAD typically uses immunomodulatory approaches in addition to immunoglobulin replacement and antibiotic prophylaxis, which are the stalwarts of bronchiectasis management in these patients. Although all antibody-deficient patients are at risk of developing bronchiectasis, ILD occurs in some forms of PAD much more commonly than in others, suggesting that distinct but poorly understood immunological factors underlie the development of this complication. Importantly, ILD can have earlier onset and may worsen survival more than bronchiectasis. Further efforts to understand the pathogenesis of lung disease in PAD will provide vital information for the most effective methods of diagnosis, surveillance, and treatment of these patients.

Non-infectious environmental antigens as a trigger for the initiation of an autoimmune skin disease

Pemphigus represents a group of organ specific autoimmune blistering disorders of the skin mediated by pathogenic autoantibodies with well-defined antigenic targets. While most of these diseases are sporadic, endemic forms of disease do exist. The endemic form of pemphigus foliaceus (also known as fogo selvagem, FS) exhibits epidemiological features that suggest exposure to hematophagous insect bites are a possible precipitating factor of this autoimmune disease, and provides a unique opportunity to study how environmental factors contribute to autoimmune disease development. FS patients and healthy individuals from endemic regions show an autoreactive IgM response that starts in early childhood and becomes restricted to IgG4 autoantibodies in FS patients. In searching for triggering environmental antigens, we have found that IgG4 and IgE autoantibodies from FS patients cross-react with a salivary antigen from sand flies. The presence of these cross-reactive antibodies and antibody genetic analysis confirming that these antibodies evolve from the same naïve B cells provides compelling evidence that this non-infectious environmental antigen could be the initial target of the autoantibody response in FS. Consequently, FS serves as an ideal model to study the impact of environmental antigens in the development of autoimmune disease.

Autoimmunity and Immune Dysregulation in Primary Immune Deficiency Disorders

Primary immune deficiencies are often associated with autoimmune disease due to the dysregulation of the immune system as a whole. In many immune deficiencies, lymphocytes may be present but dysfunctional, allowing for the development of excessive autoreactivity and resultant autoimmune disease. Autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy, autoimmune lymphoproliferative syndrome, immunodyregulation polyendocrinopathy enteropathy X-linked, IL-10/IL-10 receptor deficiencies, and PLCG2-associated antibody deficiency and immune dysregulation are disorders in which autoimmunity is a hallmark of the clinical disease presentation. In contrast, adaptive and innate immune deficiencies, which are typically defined by their infectious susceptibilities, can be associated with variable rates of autoimmune manifestations, predominantly autoimmune cytopenias. This review describes the immune dysregulation and autoimmune manifestations that may be encountered in various immune deficiencies.

Diagnosis and monitoring of IgA nephropathy: the role of biomarkers as an alternative to renal biopsy

IgA nephropathy (IgAN) is the most prevalent form of chronic glomerulonephritis in the world. The underlying pathogenesis of this autoimmune disease comprises the formation of immune complexes, including glycan-specific IgA1 or IgG antibodies and an aberrant glycosylation of IgA1. Until now, anatomopathological analysis of renal biopsies is essential for the diagnosis of IgAN and different histological classification systems have been proposed, e.g. the Oxford classification. However, a percutaneous renal biopsy is frequently not performed for several reasons and the Oxford classification system has some limitations. Since the poor prognosis of IgAN patients is partly the result of a delayed diagnosis, there is an urgent need for reliable noninvasive biomarkers that might be applicable in routine clinical practice. This article reviews the advances on the understanding of the underlying pathophysiological mechanisms of IgAN and discusses in depth the recent development of new biomarkers, including the use of proteomics and microRNAs.

Antibodies to surface dopamine-2 receptor and N-methyl-D-aspartate receptor in the first episode of acute psychosis in children

BACKGROUND

The dopamine and glutamate hypotheses are well known in psychosis. Recently, the detection of autoantibodies against proteins expressed on the surface of cells in the central nervous system has raised the possibility that specific immune-mediated mechanisms may define a biological subgroup within psychosis, although no cohort of a first episode of psychosis in children has been investigated.

METHODS

Serum taken during the acute presentation of 43 children with first episode of psychosis and serum from 43 pediatric control subjects was assessed for the presence of immunoglobulin (Ig)G, IgM, or IgA antibodies to dopamine-2 receptor (D2R) and NR1 subunit of the N-methyl-D-aspartate receptor using a flow cytometry live cell-based assay and immunolabeling of murine primary neurons.

RESULTS

Using a cutoff of three SD above the control mean, serum antibodies to D2R or NR1 were detected in 8 of 43 psychotic patients but not detected in any of 43 control subjects (p < .001). Positive immunoglobulin binding to D2R was found in 3 of 43 psychosis patients (3 IgG, 1 IgM, 0 IgA) and to N-methyl-D-aspartate receptor in 6 of 43 patients (5 IgG, 1 IgM, 1 IgA). Specificity of antibody was confirmed by immunoaffinity purification and immunoabsorption. Significant differences in antibody binding to live, fixed, and fixed and permeabilized neurons were observed, confirming that only live cells can define surface epitope immunolabeling.

CONCLUSIONS

This is the first report of serum antibodies to surface D2R and NR1 in pediatric patients with isolated psychosis, which supports the hypothesis that a subgroup of patients may be immune-mediated.

Pregnancy in women with primary biliary cirrhosis

BACKGROUND & AIMS

Primary biliary cirrhosis (PBC) may present in all decades of life, also in childbearing age. Data on maternal and fetal outcome is limited. We aimed to investigate the impact of pregnancy and childbirth on the disease course and possible effects of PBC on fetal outcome.

METHODS

Retrospective study of local cases and a compact review of published reports between 1950 and 2014.

RESULTS

Our cases along with literature review provided 98 pregnancies in 72 PBC patients. PBC was diagnosed during pregnancy in 26 (36%) patients and 46 (64%) had the diagnosis before conception. Twenty-four (30%) of the pregnancies were associated with biochemical flares and 55 (70%) with clinical improvement or stabilization. De novo onset or worsening of pruritus was seen in 49% (45/92). No maternal deaths were reported. Post-partum disease activation was observed in 60% (53/88). One patient was referred for liver transplantation after delivery. A miscarriage rate of 24% and three stillbirths were reported. Most patients were treated with ursodeoxycholic acid (UDCA) during breastfeeding and 12 patients also received UDCA during the first trimester without any identified side effects.

CONCLUSION

Most women with PBC maintain a stable disease during pregnancy, but post-partum biochemical flares are common. Symptomatic pruritus may be challenging in pregnant PBC patients. UDCA appears to be safe during pregnancy and breastfeeding. A successful pregnancy outcome is a realistic expectation for women with PBC.

Everything is autoimmune until proven otherwise

It is astounding to consider that virtually, every textbook of physiology in every medical school in the world does not include a chapter on immunology. On the other hand, virtually, in every textbook in internal medicine, immunology and immune response overlaps with every tissue and every organ. Indeed, historically, the concept of the immune response was recognized primarily in the setting of allergy and/or anaphylaxis. Indeed, the very concepts of infection, microbiology and host protection are relatively new sciences. In fact, it was little more than 100 years ago when washing hands became what is now coined "standard of care." How different it is in 2013, where one finds Handi Wipes for shoppers to use at grocery stores to protect themselves from the flora on shopping cart handles. Autoimmunity is even a newer concept without going into the well-known history of Paul Ehrlich and hemolytic anemias, the LE cell, and the beginning field of serology (and rheumatoid factor discovery). It is apparent that our understanding of autoimmunity has become linked hand-in-glove with new tools and investigational probes into serology and, more recently, the cellular immune response. With such discoveries, a number of key observations stand out. Firstly, there are a great deal more autoantibodies than there are autoimmune diseases. Second, there are a great deal more of autoimmune diseases than was believed in 1963 on the occasion of the publication of the first textbook of autoimmune diseases. Third, autoimmune diseases are, for the most part, orphan diseases, with many entities afflicting too few patients to excite the financial limb of pharmaceutical companies. In this special issue, we have grouped a number of papers, many of which were presented at the recent Congress of Autoimmunity that focus on issues that are not commonly discussed in autoimmunity. It reminds us that due to the ubiquitous nature of the innate and adaptive response, that there are a large number of diseases that have either an inflammatory and/or specific autoimmune response, we have to keep an open eye because everything is potentially autoimmune until proven otherwise.

Serum immunoglobulin M concentration is positively related to metabolic syndrome in an adult population: Tianjin Chronic Low-Grade Systemic Inflammation and Health (TCLSIH) Cohort Study

Persistent low-grade systemic inflammation has been increasingly recognized as a common pathological process, and an important contributing factor to cardiovascular diseases and its risk factor, metabolic syndrome. Immunoglobulin M is reactive to multiple autoantigens and is inferred to be important for autoimmunity, implying that immunoglobulin M may be a potential risk factor for metabolic syndrome. However, few epidemiological studies are available which are related to this potential link. Therefore, we designed a cross-sectional study of 9,379 subjects to evaluate the relationship between immunoglobulin M and metabolic syndrome in an adult population. Subjects who received health examinations were recruited from the Tianjin Medical University General Hospital-Health Management Center in Tianjin, China. Immunoglobulin M was determined with an immunonephelometric technique. Metabolic syndrome was defined according to the criteria of the American Heart Association scientific statements of 2009. Multiple logistic regression analysis was used to examine the relationships between the quartiles of immunoglobulin M and the prevalence of metabolic syndrome. After adjustment for covariates, the odds ratio of having metabolic syndrome in the fourth quartile compared with the first quartile of immunoglobulin M was 1.19 times for males (95% confidence interval, 1.002-1.41) and 1.39 times for females (95% confidence interval, 1.07-1.80). Immunoglobulin M levels also showed positive relationships with the ratio of elevated triglycerides and reduced high-density lipoprotein cholesterol in males. The study is the first to show that immunoglobulin M is independently related to metabolic syndrome and its individual components (elevated triglycerides and reduced high-density lipoprotein cholesterol) in males, whereas immunoglobulin M is independently related to metabolic syndrome in females but not to its individual components. Further studies are needed to explore the causality and the exact role of immunoglobulin M in metabolic syndrome.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

IgA deficiency and autoimmunity

IgA is the most abundant immunoglobulin in the human body, and performs a very specialized role which involves mucosal immunity, development of tolerance and protection against infection. IgA is the key immunoglobulin in the respiratory and gastrointestinal tracts, which provide the most intimate interface between the environment and self. Normal levels of IgA are based on early studies consisting of only small numbers of patients. The international consensus definition of IgA deficiency is a level of 0.07g/l after the age of four years in the absence of IgG and IgM deficiencies. The epidemiology of IgA deficiency reveals interesting variances between geographical regions - the incidence in Caucasians being much higher than that in Asians. IgA deficiency has also been found to co-exist with autoimmune diseases, allergies and malignancies. The association with autoimmunity is particularly interesting because it suggests a common genetic linkage that could potentially also explain the diversity in geoepidemiology. Both MHC and non-MHC associations have been described and the 8.1 haplotype has been significantly associated with autoimmunity in IgA deficiency patients over controls. Non-MHC genetic associations include IFIH1 and CLEC16A. The mutations leading to IgA deficiency have not been defined, but in some cases of IgA deficiency it has been suggested that the pathogenesis involves a failure in switched memory B cells that can lead to this cohort experiencing an increased incidence of recurrent bacterial infections or autoimmune diseases. Attempts to investigate the role of cytokines that can induce IgA synthesis in cells of patients with IgA deficiency, such as IL21 or the combination of CD40L/anti-CD40, IL-4 and IL10, are underway.

The limitations and hidden gems of the epidemiology of primary biliary cirrhosis

Epidemiology is expected to provide important clues to our understanding of the enigmatic etiopathogenesis of primary biliary cirrhosis (PBC). First, a systematic review of population based studies indicated a wide range in the yearly incidence (0.33-5.8/100.000) and point prevalence (1.91-40.2/100.000) rates. Though different ethnic representations may also contribute it is likely that methodological issues, based on the retrospective survey of diagnosed cases, and time trend play a major role, also in view of the prolonged asymptomatic period of the disease. Of note, the highest prevalence rates (35-40/100.000) were found in areas characterized by high medical awareness and easier access to healthcare. Second, the search for serum AMA in unselected population sera may identify the largest possible number of patients who have or will develop the disease. Indeed, a surprisingly high AMA prevalence rate, ranging between 0.43 and 1%, appears likely in the general population despite the lack of adequate work-up in most studies. Third, the median female to male ratio for PBC is classically accepted as 9-10:1 but is significantly lower for AMA prevalence (2.5:1), death certificates for PBC (4.3:1) and liver transplantation (6:1), thus suggesting that PBC in men may be underdiagnosed in early stages or manifest a more severe progression. Lastly, studies of both PBC and serum AMA prevalence among family members and monozygotic twins strongly support the role played by genetic factors in the etiopathogenesis of the disease. In conclusion, PBC epidemiology is far from being a closed case and the numerous open issues will be solved through a collaborative effort and powerful data mining tools.

Immunotherapy treatments of warm autoimmune hemolytic anemia

Warm autoimmune hemolytic anemia (WAIHA) is one of four clinical types of autoimmune hemolytic anemia (AIHA), with the characteristics of autoantibodies maximally active at body temperature. It produces a variable anemia—sometimes mild and sometimes severe. With respect to the absence or presence of an underlying condition, WAIHA is either idiopathic (primary) or secondary, which determines the treatment strategies in practice. Conventional treatments include immune suppression with corticosteroids and, in some cases, splenectomy. In recent years, the number of clinical studies with monoclonal antibodies and immunosuppressants in the treatment of WAIHA increased as the knowledge of autoimmunity mechanisms extended. This thread of developing new tools of treating WAIHA is well exemplified with the success in using anti-CD20 monoclonal antibody, Rituximab. Following this success, other treatment methods based on the immune mechanisms of WAIHA have emerged. We reviewed these newly developed immunotherapy treatments here in order to provide the clinicians with more options in selecting the best therapy for patients with WAIHA, hoping to stimulate researchers to find more novel immunotherapy strategies.

Recent insights into the role of the PD-1/PD-L1 pathway in immunological tolerance and autoimmunity

Autoimmune diseases represent a heterogeneous group of conditions whose incidence is increasing worldwide. This has stimulated studies on their etiopathogenesis, derived from a complex interaction between genetic and environmental factors, in order to improve prevention and treatment of these disorders. The relevance of T regulatory cells and of the PD-1/PD-L1 pathway in controlling immune responses has been highlighted. Recent studies have in particular elucidated the putative role of the PD-1/PD-L1 pathway in regulating T cell responses and its effects on immunological tolerance and immune-mediated tissue damage. The role of the PD-1/PD-L1 pathway in autoimmunity has been already investigated in vivo in several experimental animal models including insulin-dependent diabetes mellitus, systemic lupus erythematosus, myocarditis, encephalomyelitis, rheumatoid arthritis and inflammatory bowel diseases. With the advent of candidate gene and genome-wide association studies, single nucleotide polymorphisms (SNPs) in PD-1 gene in humans have demonstrated relevant associations with a higher risk of developing autoimmune diseases in certain ethnic groups. In this review we present recent insights into the role of the PD-1/PD-L1 pathway in regulating lymphocyte activation, promotion of T regulatory cell development and function, breakdown of tolerance and development of autoimmunity. We finally speculate on the possible development of novel therapeutic treatments in human autoimmunity by modulating the PD-1/PD-L1 pathway.

The putative role of the C1858T polymorphism of protein tyrosine phosphatase PTPN22 gene in autoimmunity

Autoimmune diseases represent a heterogeneous group of conditions whose incidence is increasing worldwide. This has stimulated studies on their etiopathogenesis, derived from a complex interaction between genetic and environmental factors, in order to improve prevention and treatment of these diseases. An increasing amount of epidemiologic investigations has associated the presence of the C1858T polymorphism in the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene to the onset of several autoimmune diseases including insulin-dependent diabetes mellitus (Type 1 diabetes). PTPN22 encodes for the lymphoid tyrosine phosphatase Lyp. This belongs to non-receptor-type protein tyrosine phosphatases involved in lymphocyte activation and differentiation. In humans, Lyp may have a role in the negative regulation of T cell receptor signaling. The single nucleotide polymorphism C1858T encodes for a more active phosphatase Lyp R620W. This has the ability to induce a higher negative regulation of T cell receptor signaling. Thus, C1858T could play an important role at the level of thymocyte polarization and escape of autoreactive T lymphocytes, through the positive selection of otherwise negatively selected autoimmune T cells. In this review we discuss the physiological role exerted by the PTPN22 gene and its encoded Lyp product in lymphocyte processes. We highlight the pathogenic significance of the C1858T PTPN22 polymorphism in human autoimmunity with special reference to Type 1 diabetes. Recently the genetic variation in PTPN22 was shown to induce altered function of T and B-lymphocytes. In particular BCR signaling defects and alterations in the B cell compartment were reported in T1D patients. We finally speculate on the possible development of novel therapeutic treatments in human autoimmunity aiming to selectively target the variant Lyp protein in autoreactive T and B lymphocytes.

Potential Roles for Infectious Agents in the Pathophysiology of Primary Biliary Cirrhosis: What's New?

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease serologically characterized by the presence of high-titer antimitochondrial antibodies and, histologically by chronic nonsuppurative cholangitis and granulomata. The aetiology of the disease remains elusive, although genetic, epigenetic, environmental, and infectious factors have been considered important for the induction of the disease in genetically prone individuals. The disease shows a striking female predominance and becomes clinically overt at the fourth to sixth decade. These characteristics have prompted investigators to consider infections that predominate in women at these ages as the likely candidates for triggering the disease. Recurrent urinary tract infections due to Escherichia coli were the first infections to be considered pathogenetically relevant. Over the years, several other microorganisms have been linked to the pathogenesis of PBC owing to epidemiological, immunological, microbiological, or experimental findings in animal models. Recent studies have provided data supporting the pathogenic role of Novosphingobium aromaticivorans and betaretroviruses. Several reports have linked other organisms to the induction of the disease and/or the maintenance of the auto-aggressive responses that are perpetuated over the course of the disease. This review highlights the findings of the most recent studies investigating the link between infections and PBC. We also discuss the close interplay of the infectious agents with other environmental and genetic factors, which may explain the multifaceted nature of this puzzling disease.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

Chipping away at a mountain: genomic studies in common variable immunodeficiency

Common variable immunodeficiency (CVID) represents one of the most frequently diagnosed disorders of the immune system. Though several causative and associated genes have been identified, the origins of most cases remain unknown. Diagnostic delay is common due to the gradual evolution and wide spectrum of phenotypes, which can include autoimmune disease, enteropathy, and lung disease. A recent genome wide array identified novel gene associations with CVID, and also showed that identification of a genetic signature via a Support Vector Machine algorithm may be a powerful diagnostic tool. Studies utilizing whole genome or exome sequencings have also met with success in identifying new causes of CVID in subgroups of patients.

Rheumatoid arthritis and primary biliary cirrhosis: cause, consequence, or coincidence?

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterized serologically by cholestasis and the presence of high-titre antimitochondrial antibodies and histologically by chronic nonsuppurative cholangitis and granulomata. PBC patients often have concomitant autoimmune diseases, including arthropathies. This raises the question as to whether there are shared features in the pathogenesis of those diseases with the pathogenesis of PBC. Epidemiological and large case studies have indicated that although the incidence of rheumatoid arthritis (RA) is not significantly raised in PBC patients, there appears to be a higher rate of RA in PBC patients and their relatives. Genetic studies have demonstrated that several genes implicated in PBC have also been implicated in RA. Epigenetic studies provided a wealth of data regarding RA, but the findings on epigenetic changes in PBC are very limited. As well, certain infectious agents identified in the pathogenesis of PBC may also play a role in the pathogenesis of RA. These data suggest that although RA is not significantly present in PBC, some individuals with certain genetic traits and environmental exposures may develop both conditions. This concept may also apply to other concomitant diseases found in PBC patients.

The immunopathology of liver granulomas in primary biliary cirrhosis

Liver granulomas and elevated serum IgM are commonly observed in patients with primary biliary cirrhosis (PBC) but their pathogenetic significance remains largely unknown. To address this issue we performed an extensive immunostaining and colocalization study of markers associated with dendritic cells and IgM in a large cohort of tissue samples from PBC and control livers as well as from non-hepatic granulomatous diseases. First, the classical dendritic cell CD11c marker is highly expressed and more sensitive than classical hematoxylin-eosin staining in detecting granulomas associated with PBC and other conditions. Second, PBC cases with CD11c-positive granulomas have significantly higher serum IgM levels and earlier disease stages. Third, granulomas from PBC and other diseases demonstrate markers of dendritic cell immaturity, i.e. CD11b, reduced MHC II, IL-23, CCR7 and CD83 expression, and elevated C1q expression. Lastly, B cells and IgM-positive plasma cells are largely represented around PBC granulomas along with macrophages. In conclusion, our comprehensive immunohistochemical study suggests that dendritic cells are key to the pathogenesis of granulomas, regardless of their origin. More specifically, PBC liver granulomas may result from the interaction between immature dendritic cells and IgM.

Tuberculosis Is Not a Risk Factor for Primary Biliary Cirrhosis: A Review of the Literature

Primary biliary cirrhosis (PBC) is a progressive cholestatic liver disease characterised serologically by cholestasis and the presence of high-titre antimitochondrial antibodies, and histologically by chronic nonsuppurative cholangitis and granulomata. As PBC is a granulomatous disease andMycobacterium tuberculosisis the most frequent cause of granulomata, a causal relation between tuberculosis and PBC has been suggested. Attempts to find serological evidence of PBC-specific autoantibodies such as AMA have been made and, conversely, granulomatous livers from patients with PBC have been investigated for molecular evidence ofMycobacterium tuberculosis. This paper discusses in detail the reported data in support or against an association betweenMycobacterium tuberculosisinfection and PBC. We discuss the immunological and microbiological data exploring the association of PBC with exposure toMycobacterium tuberculosis. We also discuss the findings of large epidemiologic studies investigating the association of PBC with preexistent or concomitant disorders and the relevance of these findings with tuberculosis. Genome-wide association studies in patients with tuberculosis as well as in patients with PBC provide conclusive hints regarding the assumed association between exposure to this mycobacterium and the induction of PBC. Analysis of these data suggest thatMycobacterium tuberculosisis an unlikely infectious trigger of PBC.