Association between IgA deficiency & other autoimmune conditions: a population-based matched cohort study

Soluble Markers of Antibody Secreting Cell Function as Predictors of Infection Risk in Rheumatoid Arthritis

Background

Rheumatoid arthritis (RA) is a systemic autoimmune disease associated with immune dysregulation and increased risk of infections. The presence of autoantibodies and immunoglobulin abnormalities indicates B-cell and antibody-secreting cell (ASC) dysfunction. We hypothesize that soluble factors associated with B-cell and ASC activity are decreased in RA patients and that this is linked to higher susceptibility to infections.

Methods

Using the Johns Hopkins Arthritis Cohort and Biorepository, we contrasted serum protein levels of soluble factors involved in B-cell activation (CD40, CD40L) and B-cell/ASC homing (CXCL10, CXCL11, and CXCL13) or survival (BAFF, APRIL, TACI, and BCMA) in 10 healthy subjects and 23 adult RA patients (aged 24-65 years). We subdivided RA patients into those with (n = 17) and those without infections (n = 6) within a 2-year period. In order to reduce the effect of RA treatment, we only included patients receiving methotrexate monotherapy or no RA treatments at baseline. Soluble serum protein levels of B-cell/ASC factors were quantified by multiplex immunoassays.

Results

We identified that (1) serum levels of soluble BCMA, APRIL, CD40, and CD40L were significantly decreased in RA patients relative to healthy individuals; (2) serum soluble BCMA, predominantly released by ASC, correlated with serum concentrations of class-switched immunoglobulins, IgG and IgA; and (3) RA patients with a history of infections had significantly lower soluble BCMA levels compared with healthy donors and with RA patients without infections.

Conclusions

Our study using soluble factors linked to B-cell/ASC activation and survival suggests that there is a paucity of ASC in a subset of RA patients and that this may be linked to altered antibody production and increased risk of infections. Further delineating the link between ASC and infection susceptibility in RA may optimize disease management and provide novel insights into disease pathogenesis that are susceptible to intervention.

Persisting enteropathy and disturbed adaptive mucosal immunity due to MHC class II deficiency

Intestinal epithelial cells (IECs) form a fundamental mucosal barrier and actively participate in tolerance and immunity against intestinal contents. Major histocompatibility complex class II (MHC II) and invariant chain (Ii) molecules are essential for adaptive immune response. MHC II deficiency often presents with gastrointestinal disorders. Intestinal biopsy samples revealed an absence of HLA-DR, Ii, and local immunoglobulins in both hematopoietic immune cells and IECs accompanied by a lack of faecal sIgA. After successful hematopoietic stem cell transplantation (HSCT) absent HLA-DR and Ii expression persisted in IECs and faecal stool analysis indicated inflammation and high microbial activity. We describe multifaceted disturbance of adaptive mucosal immunity in MHC II deficient patients suffering from enteropathy. HLA-DR and Ii expression on enterocytes is not restored by HSCT. This may account for increased susceptibility to enteric infections and intestinal inflammation leading to prolonged enteropathy reported in MHC II deficient patients.

Evaluation of screening for coeliac disease in children with juvenile idiopathic arthritis

AIM

To study the prevalence of coeliac disease (CD) in children with Juvenile idiopathic arthritis (JIA), by screening a population-based cohort of children with JIA using autoantibodies against tissue transglutaminase (anti-TG2).

METHODS

All children diagnosed with JIA in three Swedish counties, with disease onset between 2007 and 2014, were included prospectively. Serum levels of IgA anti-TG2 antibodies, IgG anti-TG2 antibodies, and total IgA were analysed. Children with positive levels of IgA anti-TG2 antibodies and children with IgA deficiency in combination with positive levels of IgG anti-TG2 antibodies were referred to the paediatric gastroenterology unit for gastroscopy and small intestine biopsy.

RESULTS

A total of 216 children were included, and analysis of IgA and IgG anti-TG2 antibodies was performed in 213 children. Three children were diagnosed with CD prior to the diagnosis of JIA, and three additional children were found through screening, resulting in a CD point prevalence of 2.8% (95% CI 0.6-5.0%).

CONCLUSION

We found a point prevalence of CD close to previous described prevalence in the general population of Swedish children. Therefore, general screening for CD in children with JIA is not supported by our data. However, this study shows that asymptomatic CD in children with JIA may be found by screening.

Primary immunodeficiency and autoimmunity: A comprehensive review

The primary immunodeficiency diseases (PIDs) include many genetic disorders that affect different components of the innate and adaptive responses. The number of distinct genetic PIDs has increased exponentially with improved methods of detection and advanced laboratory methodology. Patients with PIDs have an increased susceptibility to infectious diseases and non-infectious complications including allergies, malignancies and autoimmune diseases (ADs), the latter being the first manifestation of PIDs in several cases. There are two types of PIDS. Monogenic immunodeficiencies due to mutations in genes involved in immunological tolerance that increase the predisposition to develop autoimmunity including polyautoimmunity, and polygenic immunodeficiencies characterized by a heterogeneous clinical presentation that can be explained by a complex pathophysiology and which may have a multifactorial etiology. The high prevalence of ADs in PIDs demonstrates the intricate relationships between the mechanisms of these two conditions. Defects in central and peripheral tolerance, including mutations in AIRE and T regulatory cells respectively, are thought to be crucial in the development of ADs in these patients. In fact, pathology that leads to PID often also impacts the Treg/Th17 balance that may ease the appearance of a proinflammatory environment, increasing the odds for the development of autoimmunity. Furthermore, the influence of chronic and recurrent infections through molecular mimicry, bystander activation and super antigens activation are supposed to be pivotal for the development of autoimmunity. These multiple mechanisms are associated with diverse clinical subphenotypes that hinders an accurate diagnosis in clinical settings, and in some cases, may delay the selection of suitable pharmacological therapies. Herein, a comprehensively appraisal of the common mechanisms among these conditions, together with clinical pearls for treatment and diagnosis is presented.

The microbiome and immunodeficiencies: Lessons from rare diseases

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system, associated with a considerable increase in susceptibility to infections. PIDs can also predispose to malignancy, inflammation and autoimmunity. There is increasing awareness that some aspects of the immune dysregulation in PIDs may be linked to intestinal microbiota. Indeed, the gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both locally and systemically. Recent studies have indicated that genetic defects causing PIDs lead to perturbations in the conventional mechanisms underlying homeostasis in the gut, resulting in poor immune surveillance at the intestinal barrier, which associates with altered intestinal permeability and bacterial translocation. Consistently, a substantial proportion of PID patients presents with clinically challenging IBD-like pathology. Here, we describe the current body of literature reporting on dysbiosis of the gut microbiota in different PIDs and how this can be either the result or cause of immune dysregulation. Further, we report how infections in PIDs enhance pathobionts colonization and speculate how, in turn, pathobionts may be responsible for increased disease susceptibility and secondary infections in these patients. The potential relationship between the microbial composition in the intestine and other sites, such as the oral cavity and skin, is also highlighted. Finally, we provide evidence, in preclinical models of PIDs, for the efficacy of microbiota manipulation to ameliorate disease complications, and suggest that the potential use of dietary intervention to correct dysbiotic flora in PID patients may hold promise.

Genomic and Immunologic Drivers of Very Early-Onset Inflammatory Bowel Disease

PURPOSE OF REVIEW

Inflammatory bowel disease (IBD) is a multifactorial disease caused by dysregulated immune responses to commensal or pathogenic intestinal microbes, resulting in chronic intestinal inflammation. However, a subset of patients with IBD diagnosed <6 years of age, known as very early-onset (VEO)-IBD, can be phenotypically and genetically distinct from older onset IBD. We aim to review the clinical presentation of children with VEO-IBD and recent discoveries that point to the underlying genomic and immunologic drivers of disease, and the significant impact on our therapeutic decisions.

RECENT FINDINGS

VEO-IBD is increasing in incidence and is associated with more severe disease, aggressive progression, and poor response to most conventional therapies. This article will review some of the genetic findings in this population and the subsequent impact on therapy, with targeted approaches.

SUMMARY

Children with VEO-IBD may present with a different phenotype and more severe disease than older children and adults. An integrated approach combining genetics, immunology, and traditional IBD evaluations can lead to the identification of causal defects that directly impact management. These strategies can also be employed in older onset refractory IBD.

Tipping the balance: inhibitory checkpoints in intestinal homeostasis

The small intestinal and colonic lamina propria are populated with forkhead box P3 (FOXP3)⁺CD4⁺ regulatory T cells (Tregs) and interleukin-10-producing T cells that orchestrate intestinal tolerance to harmless microbial and food antigens. Expression of co-inhibitory receptors such as CTLA-4 and PD-1 serve as checkpoints to these cells controlling their T-cell receptor (TCR)-mediated and CD28-mediated activation and modulating the phenotype of neighboring antigen presenting cells. Recent discoveries on the diversity of co-inhibitory receptors and their selective cellular expression has shed new light on their tissue-dependent function. In this review, we provide an overview of the co-inhibitory pathways and checkpoints of Treg and effector T cells and their mechanisms of action in intestinal homeostasis. Better understanding of these inhibitory checkpoints is desired as their blockade harbors clinical potential for the treatment of cancer and their stimulation may offer new opportunities to treat chronic intestinal inflammation such as inflammatory bowel disease.

Immune/microbial interface perturbation in human IgA deficiency

In a recently published article we report the metagenomic analysis of human gut microbiomes evolved in the absence of immunoglobulin A (IgA). We show that human IgA deficiency is not associated with massive quantitative perturbations of gut microbial ecology. While our study underlines a rather expected pathobiont expansion, we at the same time highlight a less expected depletion in some typically beneficial symbionts. We also show that IgM partially supply IgA deficiency, explaining the relatively mild clinical phenotype associated with the early steps of this condition. Microbiome studies in patients should consider potential issues such as cohort size, human genetic polymorphism and treatments. In this commentary, we discuss how such issues were taken into account in our own study.

Microbiota - an amplifier of autoimmunity

Many studies describe dysbiosis as a change in the microbiota that accompanies autoimmune illnesses, but little is known about whether these changes are a cause or consequence of an altered immune state. The immune system actively shapes the composition of the microbiota, with divergent outcomes in healthy or autoimmune-prone individuals. The gut microbiota in turn acts as an acquired endocrine organ, influencing the physiology of the host via release of nutrients and chemical messengers. Dysbiosis arising from abnormal immune function can initiate or amplify autoimmunity through multiple mechanisms. We examine how the bidirectional relationship between resident microbes and the immune system contributes to autoimmune diseases.

The broad spectrum of lung diseases in primary antibody deficiencies

Human primary immunodeficiency diseases (PIDs) represent a heterogeneous group of more than 350 disorders. They are rare diseases, but their global incidence is more relevant than generally thought. The underlying defect may involve different branches of the innate and/or adaptive immune response. Thus, the clinical picture may range from severe phenotypes characterised by a broad spectrum of infections to milder infectious phenotypes due to more selective (and frequent) immune defects. Moreover, infections may not be the main clinical features in some PIDs that might present with autoimmunity, auto-inflammation and/or cancer. Primary antibody deficiencies (PADs) represent a small percentage of the known PIDs but they are the most frequently diagnosed, particularly in adulthood. Common variable immunodeficiency (CVID) is the most prevalent symptomatic PAD.

PAD patients share a significant susceptibility to respiratory diseases that represent a relevant cause of morbidity and mortality. Pulmonary complications include acute and chronic infection-related diseases, such as pneumonia and bronchiectasis. They also include immune-mediated interstitial lung diseases, such as granulomatous-lymphocytic interstitial lung disease (GLILD) and cancer. Herein we will discuss the main pulmonary manifestations of PADs, the associated functional and imaging findings, and the relevant role of pulmonologists and chest radiologists in diagnosis and surveillance.

The spectrum of lung complications in primary antibody deficiency ranges from asthma or COPD to extremely rare and specific ILDs. Early diagnosis of the underlying immune defect might significantly improve patients' lung disease, QoL and long-term prognosis.http://ow.ly/5cP230kZvOB

Dietary antioxidant micronutrients alter mucosal inflammatory risk in a murine model of genetic and microbial susceptibility

Inflammatory bowel diseases (IBD) are caused by the convergence of microbial, environmental, and genetic factors. Diet significantly alters these interactions by affecting both the host and microbiome. Using a mucosal inflammatory model that resembles the human condition of ileal pouchitis, we investigated the effects of Control (CONT) or Antioxidant (AOX) diet, containing pharmacologically relevant levels of 4 micronutrients, on disease risk in wild-type and IL-10-/- animals following surgical self-filling (SF) ileal blind loop placement. Although no differences were found in body weight change or survival, IL-10-/- CONT animals had significantly larger lymphoid organs compared with IL-10-/- AOX or with WT. SF loops from IL-10-/- CONT loop mucosa demonstrated histological inflammation, characterized by goblet cell depletion, increased mucosal myeloperoxidase (MPO), and elevated IFNγ, TNFα, and IL-17α gene expression, which AOX attenuated. AOX elevated luminal IgA in IL-10-/- animals, but not significantly in WT. In IL-10-/- animals, AOX significantly decreased the percentage of CD4 + T-bet and CD4 + RORγ T-cells compared with CONT, with no changes in CD4 + Foxp3+ Treg cells. 16S rRNA gene sequencing demonstrated AOX increased microbial alpha diversity compared with CONT in both genotypes. Notably, colonizing germ-free IL-10-/- hosts with CONT bacterial communities, but not AOX, recapitulated the inflammatory phenotype. Collectively, these findings highlight that common dietary antioxidant micronutrients reshape the gut microbial community to mitigate intestinal inflammatory profiles in genetically susceptible hosts. Insights into the dietary-immune-microbial nexus may improve understanding for recurrent inflammatory episodes in susceptible patient populations and opportunities for practical therapeutics to restore immune and microbial homeostasis.

Celiac Disease and Gluten Sensitivity

Celiac disease is an immune-mediated enteropathy triggered by gluten that affects genetically predisposed individuals, typically causing intestinal symptoms and malabsorption. Diagnosis requires stepwise evaluation with anti-tissue transglutaminase IgA and histologic analysis of the small bowel. Strict adherence to a gluten-free diet is the primary treatment. Patients with symptoms thought to be related to gluten but without evidence of celiac disease are difficult to diagnose and treat. Consider first advising general nutritional improvements. If symptoms persist, involve a trained dietitian for restrictive diets and consider evaluation for small intestinal bacterial overgrowth or other treatments for irritable bowel syndrome.

Gut microbiota and IBD: causation or correlation?

A general consensus exists that IBD is associated with compositional and metabolic changes in the intestinal microbiota (dysbiosis). However, a direct causal relationship between dysbiosis and IBD has not been definitively established in humans. Findings from animal models have revealed diverse and context-specific roles of the gut microbiota in health and disease, ranging from protective to pro-inflammatory actions. Moreover, evidence from these experimental models suggest that although gut bacteria often drive immune activation, chronic inflammation in turn shapes the gut microbiota and contributes to dysbiosis. The purpose of this Review is to summarize current associations between IBD and dysbiosis, describe the role of the gut microbiota in the context of specific animal models of colitis, and discuss the potential role of microbiota-focused interventions in the treatment of human IBD. Ultimately, more studies will be needed to define host-microbial relationships relevant to human disease and amenable to therapeutic interventions.

Significantly higher faecal counts of the yeasts candida and saccharomyces identified in people with coeliac disease

Background

Coeliac disease is an autoimmune disorder resulting from an interaction between diet, genome and immunity. The treatment of CoeD is lifelong adherence to a gluten free diet, which is associated with clinical and histological improvements. However, a substantive number of individuals report only partial symptom improvement despite both compliance with a strict gluten free diet and improvements in serological and histological biomarkers of disease activity. The role of the intestinal microbiota is an area of interest in this sub-group.

Aims

To investigate the role of yeasts and parasites in individuals reporting persistent symptoms of Coeliac disease (CoeD).

Methods

Forty-five people who met the ESPGHAN diagnostic criteria for CoeD were recruited via the Australian Coeliac Association. The faecal measures of the DNA of yeasts and parasites from the CoeD group were compared to data obtained from the medical records of non-coeliac controls with gastrointestinal symptoms from other causes.

Results

Candida sp. was detected in 33% of the CoeD group compared 0% of the control group (p = 0.000) and Saccharomyces sp. was detected in 33% of the CoeD group compared to 10% of the control group (p = 0.026). There were no differences in the presence of any of the parasite species measured.

Conclusion

Further research is required to understand the significance of Candida and Saccharomyces species in both the aetiology of CoeD and of persistent symptoms in this sub-group.

Trial Registration Clinical Trial Registration—ANZCTR Number: 12610000630011

Mucosal healing and the risk of serious infections in patients with celiac disease

Background

Patients with celiac disease (CD) are at increased risk of certain infections, but it is unknown if mucosal healing influences this risk.

Methods

We collected data on 29,096 individuals with CD (equal to villous atrophy) through Sweden's 28 pathology departments undergoing biopsy 1969-2008. Through the Swedish Patient Register we obtained information on any infection and specifically sepsis, streptococcal infection, influenza, Clostridium difficile, herpes zoster and pneumococcal infection up until December 2009. We used Cox regression to calculate hazard ratios (HRs) for the risk of future diagnosis of infection according to mucosal healing on follow-up biopsy (persistent villous atrophy vs mucosal healing).

Results

Of 5598 CD individuals with no record of any infections before follow-up biopsy, 45% had persistent villous atrophy, 619 (24%) of them had a later infection, compared to 579 (19%) in those with mucosal healing (p < 0.01); the yearly incidence was 2.1% in both groups. Adjusting for age, sex, calendar period, time between biopsies and education, persistent villous atrophy was however not associated with later infection overall (HR = 0.99; 95% CI = 0.88-1.11) or with any of the specific infections.

Conclusions

In CD, mucosal healing does not influence the risk of serious infection requiring hospital-based medical attention.

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.

Common variants at PVT1, ATG13-AMBRA1, AHI1 and CLEC16A are associated with selective IgA deficiency

Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Europeans. Our genome-wide association study (GWAS) meta-analysis of 1,635 patients with IgAD and 4,852 controls identified four new significant (P < 5 × 10-8) loci and association with a rare IFIH1 variant (p.Ile923Val). Peak new variants (PVT1, P = 4.3 × 10-11; ATG13-AMBRA1, P = 6.7 × 10-10; AHI1, P = 8.4 × 10-10; CLEC16A, P = 1.4 × 10-9) overlapped with autoimmune markers (3/4) and correlated with 21 putative regulatory variants, including expression quantitative trait loci (eQTLs) for AHI1 and DEXI and DNase hypersensitivity sites in FOXP3+ regulatory T cells. Pathway analysis of the meta-analysis results showed striking association with the KEGG pathway for IgA production (pathway P < 0.0001), with 22 of the 30 annotated pathway genes containing at least one variant with P ≤ 0.05 in the IgAD meta-analysis. These data suggest that a complex network of genetic effects, including genes known to influence the biology of IgA production, contributes to IgAD.

Myeloid-derived suppressor cells promote B-cell production of IgA in a TNFR2-dependent manner

Myeloid-derived suppressor cells (MDSCs) are well known for their capacity to suppress antitumor T-cell responses, but their effects on B-cell function and antibody production remain unclear. Here, we found that MDSCs that accumulated around the germinal center in the spleen of tumor-bearing mice co-located with B cells. In the presence of MDSCs, the antibody reaction to a surrogate antigen was significantly enhanced in mice, especially the immunoglobulin (Ig)A subtype. Co-culture with MDSCs promoted both proliferation and differentiation of B cells into IgA-producing plasma cells in vitro. Interestingly, the cross talk between MDSCs and B cells required cell-cell contact. MDSCs from tumor necrosis factor receptor (TNFR) 2^-/- mice, but not from TNFR1^-/- mice, failed to promote B-cell responses. Further investigation suggested that interleukin-10 and transforming growth factor-β1 were crucial for the MDSC-mediated promotion of IgA responses. These results demonstrate a novel mechanism of MDSC-mediated immune regulation during tumor growth.

Helicobacter pylori infection in patients with selective immunoglobulin a deficiency

Selective immunoglobulin A (IgA) deficiency (IgAD) is the most common primary immunodeficiency in the western world. The aim of the study was to investigate the prevalence and clinical characteristics of Helicobacter pylori-infected dyspeptic patients with IgAD. Case samples were drawn from all subjects ≥ 12 years of age (n = 104729) who had undergone serum total IgA measurements during 2004-14 for any reason at Leumit Healthcare Services (Israel) and had serum total IgA < 0·07 g/l. The control group was comprised of a random sample of remaining patients with a case-control ratio of 10 controls for each case. The dyspeptic diseases were identified and retrieved from Leumit Health Care Services electronic database using specific ICD-9-CM diagnostic codes. The case group included 347 subjects and the control group 3470 subjects. There were no significant differences in the prevalence of patients with dyspepsia [84 (24·2%) versus 821 (23·6%) for cases and controls, respectively]. Additionally, there was no difference in a proportion of dyspeptic H. pylori-positive subjects [59 (17·1%) versus 524 (15·1%)] between the case and control groups. Only 59 (17%) among the 347 IgAD patients underwent gastroscopy. A significantly larger proportion of case subjects experienced several forms of gastritis [13 (61·9%) versus 38 (21·6%), P < 0·001), duodenal ulcers [seven (33·3%) versus 19 (10·8%); P = 0·01] and nodular lymphoid hyperplasia (NLH) [two (9·5%) versus none; P = 0·011]. IgAD is not associated with increased prevalence of H. pylori-associated dyspepsia; nevertheless, H. pylori-infected dyspeptic IgAD subjects experience more EGD-proved gastritis, duodenal ulcers and NLH.

Salivary Immunoglobulin A Secretion Rate Is Negatively Associated with Cancer Mortality: The West of Scotland Twenty-07 Study

Immunoglobulins are essential for combating infectious disease although very high levels can indicate underlying pathology. The present study examined associations between secretory immunoglobulin A (sIgA) in saliva and mortality rates in the general population. Participants were 639 adults from the eldest cohort of the West of Scotland Twenty-07 Study aged 63 years at the time of saliva sampling in 1995. From unstimulated 2-minute saliva samples, saliva volume and S-IgA concentration were measured, and S-IgA secretion rate determined as their product. Mortality data were tracked for 19 years. Cox proportional hazard models were applied to compute hazard ratios (HR) for all-cause mortality from sIgA secretion rate. Associations were adjusted for gender, assay batch, household occupational group, smoking, medication usage, and self-reported health. There was a negative association between log sIgA secretion rate and all-cause mortality, HR = 0.81, 95%CI = 0.73–0.91, p < .001. Further analysis of specific causes of mortality revealed that the all-cause association was due to an underlying association with cancer mortality and in particular with cancers other than lung cancer. The HR for non-lung cancer was 0.68 (95%CI = 0.54 to 0.85) implying a 32% reduction in mortality risk per standard deviation rise in log sIgA secretion rate. Effects were stronger for men than women. For deaths from respiratory diseases, sIgA secretion had a non-linear relationship with mortality risk whereby only the very lowest levels of secretion were associated with elevated risk. SIgA concentration revealed a similar but weaker pattern of association. In the present study, higher secretion rates of sIgA were associated with a decreased risk of death from cancer, specifically non-lung cancer, as well as from respiratory disease. Thus, it appears that sIgA plays a protective role among older adults, and could serve as a marker of mortality risk, specifically cancer mortality.

Role of IgA receptors in the pathogenesis of IgA nephropathy

Immunoglobulin A nephropathy (IgAN) or Berger's disease is the most common form of primary glomerulonephritis in the world and one of the first causes of end-stage renal failure. IgAN is characterized by the accumulation of immune complexes containing polymeric IgA1 in mesangial areas. The pathogenesis of this disease involves the deposition of polymeric and hypogalactosylated IgA1 (Gd-IgA1) in the mesangium. Quantitative and structural changes of Gd-IgA1 play a key role in the development of the disease due to functional abnormalities of two IgA receptors: the FcαRI (CD89) expressed by blood myeloid cells and the transferrin receptor (CD71) on mesangial cells. Abnormal Gd-IgA1 induces release of soluble CD89, which participates in the formation of circulating IgA1 complexes. These complexes are trapped by CD71 that is overexpressed on mesangial cells in IgAN patients together with the crosslinking enzyme transglutaminase 2 allowing pathogenic IgA complex formation in situ and mesangial cell activation. A humanized mouse model expressing IgA1 and CD89 develops IgAN in a similar manner as patients. In this model, a food antigen, the gliadin, was shown to be crucial for circulating IgA1 complex formation and deposition, which could be prevented by a gluten-free diet. Identification of these new partners opens new therapeutic prospects for IgAN treatment.

Seronegative Celiac Disease and Immunoglobulin Deficiency: Where to Look in the Submerged Iceberg?

In the present narrative review, we analyzed the relationship between seronegative celiac disease (SNCD) and immunoglobulin deficiencies. For this purpose, we conducted a literature search on the main medical databases. SNCD poses a diagnostic dilemma. Villous blunting, intraepithelial lymphocytes (IELs) count and gluten "challenge" are the most reliable markers. Immunohistochemistry/immunofluorescence tissue transglutaminase (tTG)-targeted mucosal immunoglobulin A (IgA) immune complexes in the intestinal mucosa of SNCD patients may be useful. In our experience, tTG-mRNA was similarly increased in seropositive celiac disease (CD) and suspected SNCD, and strongly correlated with the IELs count. This increase is found even in the IELs' range of 15-25/100 enterocytes, suggesting that there may be a "grey zone" of gluten-related disorders. An immune deregulation (severely lacking B-cell differentiation) underlies the association of SNCD with immunoglobulin deficiencies. Therefore, CD may be linked to autoimmune disorders and immune deficits (common variable immunodeficiency (CVID)/IgA selective deficiency). CVID is a heterogeneous group of antibodies dysfunction, whose association with CD is demonstrated only by the response to a gluten-free diet (GFD). We hypothesized a familial inheritance between CD and CVID. Selective IgA deficiency, commonly associated with CD, accounts for IgA-tTG seronegativity. Selective IgM deficiency (sIgMD) is rare (<300 cases) and associated to CD in 5% of cases. We diagnosed SNCD in a patient affected by sIgMD using the tTG-mRNA assay. One-year GFD induced IgM restoration. This evidence, supporting a link between SNCD and immunoglobulin deficiencies, suggests that we should take a closer look at this association.

[Is familial screening useful in selective immunoglobulin A deficiency?]

INTRODUCTION

Selective immunoglobulin A deficiency (SIgAD), the most common primary immunodeficiency, is often asymptomatic. High rates of familial clustering have been described in SIgAD, but the causative genetic defect and mechanism of inheritance are unknown.

OBJECTIVES

To determine whether familial SIgAD cases show more severe clinical and immunological characteristics than sporadic ones; to investigate the utility of screening first-degree relatives (FDRs) of these patients, and to determine whether symptoms in affected family members are important enough to justify screening.

PATIENTS AND METHODS

Descriptive, cross-sectional study (October 2010-September 2011) of all patients with SIgAD and followed up in our center. Demographic, clinical, and analytical data were reviewed. A familial case was defined as an SIgAD patient with at least one affected FDR.

RESULTS

Of the 130 participants, 42 were SIgAD patients and 88 FDR. There were 13 (31%) familial cases and and 14 (16%) affected FDRs. Six family members had to be analyzed in order to detect one affected one. There were no clinical differences between familial and sporadic SIgAD cases. The percentages of intestinal disease (p=001, OR=9.57, 95%CI 2.59-35.3), hospitalizations (p=045, OR=4.01; 95%CI 1.10-14.67], and need for chronic treatment (p=006, OR=5.5; 95%CI 1.57-19.54) were higher in affected FDRs than in unaffected ones.

CONCLUSIONS

The symptoms were not more severe in familial than sporadic SIgAD cases. Nonetheless, the elevated prevalence of affected FDRs with significant morbidity may justify routine screening of close family members of these patients.

Selective immunoglobulin a deficiency in type 1 diabetes mellitus: a prevalence study in Western sicily (Italy)

BACKGROUND

The association between type 1 diabetes and immunoglobulin A deficiency (IgA-D) has long been recognized in many populations. The aim of this study was to assess the prevalence of IgA-D in patients with type 1 diabetes mellitus all coming from a defined geographical area and to investigate the clinical features of these subjects.

METHODS

The records of 150 consecutive patients with type 1 diabetes mellitus referred in a period of one year were analyzed. A detailed history was obtained for each patient. Information was collected concerning age, gender, time of onset of diabetes, and presence of other autoimmune diseases.

RESULTS

Out of 150 patients with type 1 diabetes, eight (5.3%) had a diagnosis of IgA-D. There were one female and seven male; all these patients were diagnosed by screening: none of them had history of recurrent infections. Autoimmune thyroiditis was coexisting in five patients (62%). Although other associated autoimmune disorders were found in a number of patients, there was no different prevalence rate in IgA deficient patients.

CONCLUSION

This study shows the prevalence of IgA-D in Sicilian patients with type 1 diabetes as 5.3% which is much higher than reported in other Italian studies. Moreover, our data show a high prevalence of IgA-D in male gender and describe thyroiditis as the most frequent autoimmune disease present in these patients. Finally, in our case report, IgA-D diagnosis always followed routine IgA measurement when case finding for celiac disease with no history of recurrent infections in each patient.

IgA deficiency and risk of cancer: a population-based matched cohort study

PURPOSE

To investigate the risk of cancer in individuals with IgA deficiency compared with the general population.

METHODS

Prospective nationwide population-based cohort study. We identified 2320 individuals with IgA deficiency (IgA levels < 0.07 g/L) diagnosed between 1980 and 2010 in six Swedish university hospitals. Individuals with IgA deficiency were then matched on age, sex, place of residence, and year of diagnosis with up to 10 general population controls (n = 23,130). Through linkage with the Swedish Cancer Register we calculated conditional hazard ratios (HRs) for cancer diagnosed after IgA deficiency diagnosis in patients without a previous cancer diagnosis.

RESULTS

During follow-up, 125 individuals with IgA deficiency (61/10,000 person-years) and 984 controls (47/10,000 person-years) developed cancer (HR 1.31; 95%CI = 1.09-1.58). In cause-specific analyses, we found an increased risk of any gastrointestinal cancer (HR = 1.64; 95%CI = 1.07-2.50), but not for lymphoproliferative malignancy (HR 1.68; 95%CI = 0.89-3.19). Relative risk estimates for overall cancer were very high in the first year of follow-up (overall: HR = 2.80; 95%CI = 1.74-4.49), but failed to reach statistical significance thereafter. IgA deficiency diagnosed in childhood (n = 487) was not associated with overall cancer (HR = 3.26; 0.88-12.03).

CONCLUSIONS

Individuals with IgA deficiency are at a moderately increased risk of cancer, with excess risks of gastrointestinal cancer. This excess risk is highest just after diagnosis suggesting a degree of surveillance bias. Children with IgA deficiency were at no increased risk of cancer but the statistical power was limited in subanalyses.

Cooperativity among secretory IgA, the polymeric immunoglobulin receptor, and the gut microbiota promotes host-microbial mutualism

Secretory IgA (SIgA) antibodies in the intestinal tract form the first line of antigen-specific immune defense, preventing access of pathogens as well as commensal microbes to the body proper. SIgA is transported into external secretions by the polymeric immunoglobulin receptor (pIgR). Evidence is reported here that the gut microbiota regulates production of SIgA and pIgR, which act together to regulate the composition and activity of the microbiota. SIgA in the intestinal mucus layer helps to maintain spatial segregation between the microbiota and the epithelial surface without compromising the metabolic activity of the microbes. Products shed by members of the microbial community promote production of SIgA and pIgR by activating pattern recognition receptors on host epithelial and immune cells. Maternal SIgA in breast milk provides protection to newborn mammals until the developing intestinal immune system begins to produce its own SIgA. Disruption of the SIgA-pIgR-microbial triad can increase the risk of infectious, allergic and inflammatory diseases of the intestine.