The role of IgA and IgA Fc receptors as anti-inflammatory agents

Distinctive profile of monomeric and polymeric anti-SSA/Ro52 immunoglobulin A1 isoforms in saliva of patients with primary Sjögren's syndrome and Sicca

OBJECTIVE

Primary Sjögren's syndrome (pSS) is the second most common chronic autoimmune connective tissue disease. Autoantibodies, immunoglobulin (IgG) anti-SSA/Ro, in serum is a key diagnostic feature of pSS. Since pSS is a disease of the salivary gland, we investigated anti-SSA/Ro52 in saliva.

METHODS

Using a novel electrochemical detection platform, Electric Field-Induced Release and Measurement, we measured IgG/M/A, IgG, IgA, IgA isotypes (IgA1 and IgA2) and IgA1 subclasses (polymeric and monomeric IgA1) to anti-SSA/Ro52 in saliva supernatant of 34 pSS, 35 dry eyes and dry mouth (patients with Sicca) and 41 health controls.

RESULTS

Saliva IgG/M/A, IgG, IgA, IgA isotypes and IgA1 subclasses to anti-SSA/Ro52 differed significantly between pSS, non-pSS Sicca and healthy subjects. Elevated monomeric IgA1 was observed in patients with non-pSS Sicca while elevated polymeric IgA1 (pIgA1) was observed in patients with pSS. Salivary polymeric but not monomeric IgA1 (mIgA1) isoform correlated with focus score (r2=0.467, p=0.001) CONCLUSIONS: Salivary anti-Ro52 polymeric IgA1 isoform is associated with glandular inflammation in pSS, while salivary monomeric IgA1 is associated with Sicca. Whether IgA1 isotope switching plays a role in the progression of the Sicca to pSS warrants further investigation.

Secretory Immunoglobulin A Immunity in Chronic Obstructive Respiratory Diseases

Chronic obstructive pulmonary disease (COPD), asthma and cystic fibrosis (CF) are distinct respiratory diseases that share features such as the obstruction of small airways and disease flare-ups that are called exacerbations and are often caused by infections. Along the airway epithelium, immunoglobulin (Ig) A contributes to first line mucosal protection against inhaled particles and pathogens. Dimeric IgA produced by mucosal plasma cells is transported towards the apical pole of airway epithelial cells by the polymeric Ig receptor (pIgR), where it is released as secretory IgA. Secretory IgA mediates immune exclusion and promotes the clearance of pathogens from the airway surface by inhibiting their adherence to the epithelium. In this review, we summarize the current knowledge regarding alterations of the IgA/pIgR system observed in those major obstructive airway diseases and discuss their implication for disease pathogenesis.

Accounting for B-cell Behavior and Sampling Bias Predicts Anti-PD-L1 Response in Bladder Cancer

Cancer immunotherapy is predominantly based on T cell-centric approaches. At the same time, the adaptive immune response in the tumor environment also includes clonally produced immunoglobulins and clonal effector/memory B cells that participate in antigen-specific decisions through their interactions with T cells. Here, we investigated the role of infiltrating B cells in bladder cancer via patient dataset analysis of intratumoral immunoglobulin repertoires. We showed that the IgG1/IgA ratio is a prognostic indicator for several subtypes of bladder cancer and for the whole IMVigor210 anti-PD-L1 immunotherapy study cohort. A high IgG1/IgA ratio associated with the prominence of a cytotoxic gene signature, T-cell receptor signaling, and IL21-mediated signaling. Immunoglobulin repertoire analysis indicated that effector B-cell function, rather than clonally produced antibodies, was involved in antitumor responses. From the T-cell side, we normalized a cytotoxic signature against the extent of immune cell infiltration to neutralize the artificial sampling-based variability in immune gene expression. Resulting metrics reflected proportion of cytotoxic cells among tumor-infiltrating immune cells and improved prediction of anti-PD-L1 responses. At the same time, the IgG1/IgA ratio remained an independent prognostic factor. Integration of the B-cell, natural killer cell, and T-cell signatures allowed for the most accurate prediction of anti-PD-L1 therapy responses. On the basis of these findings, we developed a predictor called PRedIctive MolecUlar Signature (PRIMUS), which outperformed PD-L1 expression scores and known gene signatures. Overall, PRIMUS allows for reliable identification of responders among patients with muscle-invasive urothelial carcinoma, including the subcohort with the low-infiltrated "desert" tumor phenotype.

The Epidemiology and Clinical Presentations of Atopic Diseases in Selective IgA Deficiency

Selective IgA deficiency (sIgAD) is the most common primary immunodeficiency disease (PID), with an estimated occurrence from about 1:3000 to even 1:150, depending on population. sIgAD is diagnosed in adults and children after the 4th year of age, with immunoglobulin A level below 0.07 g/L and normal levels of IgM and IgG. Usually, the disease remains undiagnosed throughout the patient's life, due to its frequent asymptomatic course. If symptomatic, sIgAD is connected to more frequent viral and bacterial infections of upper respiratory, urinary, and gastrointestinal tracts, as well as autoimmune and allergic diseases. Interestingly, it may also be associated with other PIDs, such as IgG subclasses deficiency or specific antibodies deficiency. Rarely sIgAD can evolve to common variable immunodeficiency disease (CVID). It should also be remembered that IgA deficiency may occur in the course of other conditions or result from their treatment. It is hypothesized that allergic diseases (e.g., eczema, rhinitis, asthma) are more common in patients diagnosed with this particular PID. Selective IgA deficiency, although usually mildly symptomatic, can be difficult for clinicians. The aim of the study is to summarize the connection between selective IgA deficiency and atopic diseases.

Microbiota-host interactions shape ageing dynamics

Occupying the interface between host and environment, host-associated microbes play fundamental roles in nutrient absorption, essential metabolite synthesis, development of the immune system, defence against pathogens and pathogenesis. Microbiota composition and function is rather stable during adulthood, while it dramatically changes during early development, frailty and disease. Ageing is associated with progressive decrease of homeostasis, often resulting in disruption of the physiological balance between host and commensal microbes, ultimately leading to dysbiosis and host demise. Generally, high microbial diversity is associated with health and a youthful state, while low individual microbial diversity and larger inter-individual microbial diversity is associated with ageing and disease states. Different species are equipped with species-specific commensal, symbiotic and pathogenic microbial communities. How and whether the specific host-microbiota consortia co-evolved with host physiology to ensure homeostasis and promote individual fitness remains an open question. In this essay, we propose that the evolution of vertebrate-specific immune adaptations may have enabled the establishment of highly diverse, species-specific commensal microbial communities. We discuss how the maintenance of intact immune surveillance mechanisms, which allow discrimination between commensal and pathogenic bacteria, fail during ageing and lead to the onset of known ageing-related diseases. We discuss how host-microbiota interactions are key to maintaining homeostasis despite external perturbations, but also how they affect a range of host-specific ageing-related phenotypes. This article is part of the theme issue 'The role of the microbiome in host evolution'.

Serum IgA Fc effector functions in infectious disease and cancer

Immunoglobulin (Ig) A is the most abundant antibody isotype present at mucosal surfaces and the second most abundant in human serum. In addition to preventing pathogen entry at mucosal surfaces, IgA can control and eradicate bacterial and viral infections through a variety of antibody‐mediated innate effector cell mechanisms. The role of mucosal IgA in infection (e.g. neutralization) and in inflammatory homeostasis (e.g. allergy and autoimmunity) has been extensively investigated; by contrast, serum IgA is comparatively understudied. IgA binding to fragment crystallizable alpha receptor plays a dual role in the activation and inhibition of innate effector cell functions. Mounting evidence suggests that serum IgA induces potent effector functions against various bacterial and some viral infections including Neisseria meningitidis and rotavirus. Furthermore, in the era of immunotherapy, serum IgA provides an interesting alternative to classical IgG monoclonal antibodies to treat cancer and infectious pathogens. Here we discuss the role of serum IgA in infectious diseases with reference to bacterial and viral infections and the potential for IgA as a monoclonal antibody therapy.

IgA: Structure, Function, and Developability

Immunoglobulin A (IgA) plays a key role in defending mucosal surfaces against attack by infectious microorganisms. Such sites present a major site of susceptibility due to their vast surface area and their constant exposure to ingested and inhaled material. The importance of IgA to effective immune defence is signalled by the fact that more IgA is produced than all the other immunoglobulin classes combined. Indeed, IgA is not just the most prevalent antibody class at mucosal sites, but is also present at significant concentrations in serum. The unique structural features of the IgA heavy chain allow IgA to polymerise, resulting in mainly dimeric forms, along with some higher polymers, in secretions. Both serum IgA, which is principally monomeric, and secretory forms of IgA are capable of neutralising and removing pathogens through a range of mechanisms, including triggering the IgA Fc receptor known as FcαRI or CD89 on phagocytes. The effectiveness of these elimination processes is highlighted by the fact that various pathogens have evolved mechanisms to thwart such IgA-mediated clearance. As the structure–function relationships governing the varied capabilities of this immunoglobulin class come into increasingly clear focus, and means to circumvent any inherent limitations are developed, IgA-based monoclonal antibodies are set to emerge as new and potent options in the therapeutic arena.

Monomeric Immunoglobulin A from Plasma Inhibits Human Th17 Responses In Vitro Independent of FcαRI and DC-SIGN

Circulating immunoglobulins including immunoglobulin G (IgG) and IgM play a critical role in the immune homeostasis by modulating functions of immune cells. These functions are mediated in part by natural antibodies. However, despite being second most abundant antibody in the circulation, the immunoregulatory function of IgA is relatively unexplored. As Th17 cells are the key mediators of a variety of autoimmune, inflammatory, and allergic diseases, we investigated the ability of monomeric IgA (mIgA) isolated from pooled plasma of healthy donors to modulate human Th17 cells. We show that mIgA inhibits differentiation and amplification of human Th17 cells and the production of their effector cytokine IL-17A. mIgA also suppresses IFN-γ responses under these experimental conditions. Suppressive effect of mIgA on Th17 responses is associated with reciprocal expansion of FoxP3-positive regulatory T cells. The effect of mIgA on Th17 cells is dependent on F(ab′)₂ fragments and independent of FcαRI (CD89) and DC-SIGN. Mechanistically, the modulatory effect of mIgA on Th17 cells implicates suppression of phosphorylation of signal transducer and activator of transcription 3. Furthermore, mIgA binds to CD4⁺ T cells and recognizes in a dose-dependent manner the receptors for cytokines (IL-6Rα and IL-1RI) that mediate Th17 responses. Our findings thus reveal novel anti-inflammatory functions of IgA and suggest potential therapeutic utility of mIgA in autoimmune and inflammatory diseases that implicate Th17 cells.

Differential Gene Expression Associated with Meningeal Injury in Acute Mild Traumatic Brain Injury

Injury to the meninges is not uncommon after traumatic brain injury (TBI), yet minimal research has been directed toward understanding the relevant biology. After a concussive event, the meninges are observed to abnormally enhance on post-contrast magnetic resonance imaging (MRI) in some patients, but not all. The aim of this work is to identify genes differentially expressed in patients with meningeal injury. Patients presenting to the emergency room with suspected TBI received a standard research MRI and blood draw within 48 h of injury. Two groups of patients were included: those with and without abnormal enhancement of the meninges on post-contrast MRI, both without other imaging findings. Groups were compared on microarray gene expression in peripheral blood samples using Affymetrix (Santa Clara, CA) and Partek Genomics Suite (Partek, Inc., St. Louis, MO) software (false discovery rate, <0.05). Forty patients were enrolled with a time from injury to MRI/blood draw of 16.8 h (interquartile range, 7.5-24.1). We observed 76 genes to be differentially expressed in patients with meningeal injury compared to those without, such as receptor for Fc fragment of IgA, multiple C2 domains, transmembrane 2, and G-protein-coupled receptor 27, which have been previously associated with initiating inflammatory mediators, phagocytosis, and other regulatory mechanisms. Post-contrast MRI is able to detect meningeal injury and has a unique biological signature observed through gene expression. These findings suggest that an acute inflammatory response occurs in response to injury to the meninges following a concussion.

Critical Role of Kupffer Cell CD89 Expression in Experimental IgA Nephropathy

Although IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, its etiology remains only partly understood. It is clear that the pathogenesis of IgAN involves the formation of macromolecular IgA1 complexes and increased levels of serum IgA1 and IgA1-immune complexes(IC), due to defective IgA1 clearance. Previous studies suggest that the blood and tissue myeloid cell-expressed IgA Fc receptor (FcαR/CD89) mediates IgA-IC clearance and its dysfunction, via decreased activity or excessive levels of soluble FcαR/sCD89 induces IgAN. Such a mechanism requires robust stimulation of IgAN levels via forced expression of CD89. In the absence of unequivocal evidence supporting such a mechanism to date, we attempted to test the extent of CD89-evoked IgAN by generating a transgenic mouse strain expressing human CD89 under the control of murine CD14 promotor. No deposition of IgA-CD89 complexes or glomerulonephritis was detected, however. Further studies showed that elimination of murine IgA was mediated by Kupffer cells. In patients, however, CD89/IgA complexes were detected, and injection of patient IgA induced IgAN-like features in CD89 Tg mice. In transgenic mice, IgAN pathogenesis involves impaired clearance of abnormal IgA via CD89, primarily by the Kupffer cells. Conditional IgAN progression in CD89 transgenic mice thus reveals important aspects of IgAN pathogenesis.

IgA directly inhibits antigen-dependent B cell activation following distinctive distribution of the antigen in mice

CONTEXT

Serum IgA suppresses immune responses when exposed to antigens recognized by the antibody; however, the underlying mechanism remains unclear.

OBJECTIVE

We herein clarified the relationships between changes in antigen distribution and antigen-dependent B cell activation in the presence or absence of IgA against the antigen in mice.

MATERIALS AND METHODS

DBA/1J and HR-1 mice were intravenously injected with ovalbumin (OVA) and anti-OVA monoclonal IgA OA-4. The distribution of the antigen and B cell responses were measured.

RESULTS

B cell activation by injected OVA, namely, increases in anti-OVA IgG production and the populations of B220(+)GL7(+) and B220(+)CD69(high) splenocytes, was diminished by the co-injection of OA-4. Co-injected OA-4 increased OVA in the serum as well as in the bile and gut. This was coincident with its decrease in the urine due to the inhibition of OVA monomer secretion through the formation of immune complexes. The apparent similarities in the association between fluorescein isothiocyanate (FITC)-OVA and splenic B cells in the presence and absence of OA-4 in vivo appeared to be attributed to compensation between the two effects of OA-4; an increase in serum OVA in vivo and inhibition of the association between OVA and B cells, as suggested by in vitro experiments.

DISCUSSION

Based on these results, the stimulation of B cells by OVA may be directly reduced, at least partly, by the neutralization of OVA by OA-4.

CONCLUSION

IgA may be an effective drug for the treatment of immune disorders due to its ability to blunt antigen-specific B cell activation.

High-dimensional immune profiling of total and rotavirus VP6-specific intestinal and circulating B cells by mass cytometry

In-depth phenotyping of human intestinal antibody secreting cells (ASCs) and their precursors is important for developing improved mucosal vaccines. We used single-cell mass cytometry to simultaneously analyze 34 differentiation and trafficking markers on intestinal and circulating B cells. In addition, we labeled rotavirus (RV) double-layered particles with a metal isotope and characterized B cells specific to the RV VP6 major structural protein. We describe the heterogeneity of the intestinal B-cell compartment, dominated by ASCs with some phenotypic and transcriptional characteristics of long-lived plasma cells. Using principal component analysis, we visualized the phenotypic relationships between major B-cell subsets in the intestine and blood, and revealed that IgM(+) memory B cells (MBCs) and naive B cells were phenotypically related as were CD27(-) MBCs and switched MBCs. ASCs in the intestine and blood were highly clonally related, but associated with distinct trajectories of phenotypic development. VP6-specific B cells were present among diverse B-cell subsets in immune donors, including naive B cells, with phenotypes representative of the overall B-cell pool. These data provide a high dimensional view of intestinal B cells and the determinants regulating humoral memory to a ubiquitous, mucosal pathogen at steady-state.

FcRγ-chain deficiency reduces the development of diet-induced obesity

OBJECTIVE

Pathogenic immunoglobulins are produced during the development of obesity and contribute to the development of insulin resistance (IR). However, the mechanisms by which these antibodies affect IR are largely unknown. This study investigated whether Fc-receptors contribute to the development of diet-induced obesity and IR by studying FcRγ(-/-) mice that lack the γ-subunit necessary for signaling and cell surface expression of FcγR and FcεRI.

METHODS

FcRγ(-/-) and wild-type (WT) mice were fed a high-fat diet (HFD) to induce obesity. At 4 and 11 weeks, body weight and insulin sensitivity were measured, and adipose tissue (AT) inflammation was determined. Furthermore, intestinal triglyceride (TG) uptake and plasma TG clearance were determined, and gut microbiota composition was analyzed.

RESULTS

FcRγ(-/-) mice gained less weight after 11 weeks of HFD. They had reduced adiposity, adipose tissue inflammation, and IR. Interestingly, FcRγ(-/-) mice had higher lean mass compared to WT mice, which was associated with increased energy expenditure. Intestinal TG absorption was increased whereas plasma TG clearance was not affected in FcRγ(-/-) mice. Gut microbial composition differed significantly and might therefore have added to the observed phenotype.

CONCLUSIONS

FcRγ-chain deficiency reduces the development of diet-induced obesity, as well as associated AT inflammation and IR at 11 weeks of HFD.

Update on immunoglobulin A nephropathy, Part I: Pathophysiology

Immunoglobulin A (IgA) nephropathy is one of the most common glomerulonephritis and its frequency is probably underestimated because in most patients the disease has an indolent course and the kidney biopsy is essential for the diagnosis. In the last years its pathogenesis has been better identified even if still now several questions remain to be answered. The genetic wide association studies have allowed to identifying the relevance of genetics and several putative genes have been identified. The genetics has also allowed explaining why some ancestral groups are affected with higher frequency. To date is clear that IgA nephropathy is related to auto antibodies against immunoglobulin A1 (IgA1) with poor O-glycosylation. The role of mucosal infections is confirmed, but which are the pathogens involved and which is the role of Toll-like receptor polymorphism is less clear. Similarly to date whether the disease is due to the circulating immunocomplexes deposition on the mesangium or whether the antigen is already present on the mesangial cell as a “lanthanic” deposition remains to be clarified. Finally also the link between the mesangial and the podocyte injury and the tubulointerstitial scarring, as well as the mechanisms involved need to be better clarified.

Re-thinking the functions of IgA(+) plasma cells

The intestinal mucosa harbors the largest population of antibody (Ab)-secreting plasma cells (PC) in the human body, producing daily several grams of immunoglobulin A (IgA). IgA has many functions, serving as a first-line barrier that protects the mucosal epithelium from pathogens, toxins and food antigens (Ag), shaping the intestinal microbiota, and regulating host-commensal homeostasis. Signals induced by commensal colonization are central for regulating IgA induction, maintenance, positioning and function and the number of IgA(+) PC is dramatically reduced in neonates and germ-free (GF) animals. Recent evidence demonstrates that the innate immune effector molecules tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) are required for IgA(+) PC homeostasis during the steady state and infection. Moreover, new functions ascribed to PC independent of Ab secretion continue to emerge, suggesting that PC, including IgA(+) PC, should be re-examined in the context of inflammation and infection. Here, we outline mechanisms of IgA(+) PC generation and survival, reviewing their functions in health and disease.

Strategic characterization of anti-drug antibody responses for the assessment of clinical relevance and impact

All therapeutic proteins have the potential to induce anti-drug antibodies (ADA). Clinically relevant ADA can impact efficacy and/or safety of a biological therapeutic. Immunogenicity assessment strategy evaluates binding and neutralizing ADA, and the need for additional characterization (e.g., epitope, titer and so on) is determined using a risk-based approach. The choice of characterization assays depends on the type, application and immunogenicity of the therapeutic. ADA characterization can impact the interpretation of the risk profile of a given therapeutic, and offers insight into opportunities for risk mitigation and management. This article describes common ADA characterization methods. Strategic assessment and characterization of clinically relevant ADA are discussed, in order to support clinical options for safe and effective patient care and disease management.

New insights into the pathogenesis of IgA nephropathy

IgA nephropathy (IgAN) is the most common diagnosis amongst primary glomerular diseases in most countries where renal biopsies are regularly performed. Only a fraction of these patients is at high risk of losing glomerular filtration rate (GFR) in particular those with high grade proteinuria, uncontrolled hypertension or already impaired GFR at diagnosis, and those with renal scars in the renal biopsy. Genetic modifiers of IgAN onset and/or course are emerging. Spontaneous animal models of IgAN are problematic given considerable species differences between the rodent and human IgA system. However, new transgenic models help to better understand the pathogenesis. A key pathogenetic role appears to be played by underglycated IgA1 as well as autoantibodies to these IgA glycoforms and IgA receptors such as CD89 and transferrin receptor 1. Once IgA and/or IgA-containing immune complexes are deposited or formed in the mesangium, secondary effector mechanisms become important including complement activation, release of mesangial growth factors (in particular platelet-derived growth factor), and finally non-IgAN-specific events that culminate in glomerular and subsequently renal tubulointerstitial scaring. Here, we review these processes and describe potential novel therapeutic targets in IgAN.

Potential of immunoglobulin A to prevent allergic asthma

Allergic asthma is characterized by bronchial hyperresponsiveness, a defective barrier function, and eosinophilic lower airway inflammation in response to allergens. The inflammation is dominated by Th2 cells and IgE molecules and supplemented with Th17 cells in severe asthma. In contrast, in healthy individuals, allergen-specific IgA and IgG4 molecules are found but no IgE, and their T cells fail to proliferate in response to allergens, probably because of the development of regulatory processes that actively suppress responses to allergens. The presence of allergen-specific secretory IgA has drawn little attention so far, although a few epidemiological studies point at a reverse association between IgA levels and the incidence of allergic airway disease. This review highlights the latest literature on the role of mucosal IgA in protection against allergic airway disease, the mechanisms described to induce secretory IgA, and the role of (mucosal) dendritic cells in this process. Finally, we discuss how this information can be used to translate into the development of new therapies for allergic diseases based on, or supplemented with, IgA boosting strategies.

Frequent intratype neutralization by plasma immunoglobulin a identified in HIV type 2 infection

Human immunodeficiency virus type 2 (HIV-2) is less transmissible and less pathogenic compared to HIV-1 and, when matched for CD4(+) T cell count, the plasma viral load in HIV-2-infected individuals is approximately one log lower than in HIV-1-infected individuals. The explanation for these observations is elusive, but differences in virus controlling immunity generated in the two infections may be contributing factors. In the present study, we investigated neutralization by immunoglobulin A (IgA), in parallel with IgG, purified from plasma of HIV-1, HIV-2, and HIV-1/HIV-2 dually (HIV-D) infected individuals. Neutralization was analyzed against HIV-1 and HIV-2 isolates using a plaque reduction assay. In HIV-2 infection, intratype-specific neutralization by IgA was frequently detected, although at a lesser magnitude then the corresponding IgG neutralizing titers. In contrast, neutralization by IgA could rarely be demonstrated in HIV-1 infection despite similar plasma IgA levels in both infections. In addition, IgA and IgG of HIV-D plasma neutralized the HIV-2 isolate more potently than the HIV-1 isolate, suggesting that the difference between neutralizing activity of plasma IgA and IgG depends on the virus itself. Taken together, these findings suggest that both IgA and IgG add to the potent intratype neutralizing activity detected in HIV-2 plasma, which may contribute to virus control in HIV-2 infection.

Distinct characteristics of antibody responses against factor VIII in healthy individuals and in different cohorts of hemophilia A patients

Neutralizing antibodies against factor VIII (FVIII) remain the major complication in the replacement therapy of hemophilia A patients. To better understand the evolution of these antibodies it is important to generate comprehensive datasets which include both neutralizing and nonneutralizing antibodies, their isotypes, and IgG subclasses. We developed sensitive ELISAs to analyze FVIII-binding antibodies in different cohorts of hemophilia A patients and in healthy individuals. Our data reveal the prevalence of FVIII-binding antibodies among healthy individuals (n = 600) to be as high as 19%, with a prevalence of antibody titers > or =1:80 of 2%. The prevalence of FVIII-binding antibodies was 34% (5% for titers > or =1:80) in patients without FVIII inhibitors (n = 77), 39% (4% for titers > 1:80) in patients after successful immune tolerance induction therapy (n = 23), and 100% (n = 20, all titers > or =1:80) in patients with FVIII inhibitors. We found significant differences for IgG subclasses of FVIII-binding antibodies between the different study cohorts. IgG4 and IgG1 were the most abundant IgG subclasses in patients with FVIII inhibitors. Strikingly, IgG4 was completely absent in patients without FVIII inhibitors and in healthy subjects. These findings point toward a distinct immune regulatory pathway responsible for the development of FVIII-specific IgG4 associated with FVIII inhibitors.

Clinical characteristics and favorable long-term outcomes for patients with idiopathic inflammatory myopathies: a retrospective single center study in China

Background

Little is known about the clinical features and true survival risk factors in Chinese Han population. We conducted the current study to investigate the clinical features, long-term outcome and true potential indicators associated with mortality of idiopathic inflammatory myopathies (IIM) in China.

Methods

We restrospectvely investigated 188 patients diagnosed with IIM at our hospital from January 1986 to April 2009. The primary outcome was determined with mortality. The secondary outcomes for survival patients were organ damage and disease activity, health status, and disability, which were assessed with Myositis Damage Index, Myositis Disease Activity Assessment Visual Analogue Scales, Health Assessment Questionnaire Disability Index, and the Modified Rankin Scale, respectively. Potential prognostic factors for mortality were analyzed with the multivariate Cox regression model.

Results

Mean age at disease onset was 43.8 ± 15.8 years and male to female ratio was 1:2.1 in this cohort. The 1-, 5-, 10-, 15- and 20-year survival rates were 93.6%, 88.7%, 81%, 73.6% and 65.6%. The independent predicators for mortality were age at disease onset [hazard ratio (HR):1.05, 95% CI 1.02 - 1.08], presence of cancer (HR:3.68, 95%CI 1.39 - 9.74), and elevated IgA level at diagnosis (HR:2.80, 95% CI 1.16-6.74). At the end of the follow-up, 29 patients manifested drug withdrawal within an average 4.1 years (range 0.5-15.2 year), most patients (85.9%) had no disease activity and 130 patients (83.4%) had no disability.

Conclusions

The long-term outcomes of IIM patients in our cohort have improved dramatically. Those patients most likely to survive had a high chance of reaching stable disease status, and obtained long-term or possibly permanent remission to a large extent.

The human immunoglobulin A Fc receptor FcαRI: a multifaceted regulator of mucosal immunity

Immunoglobulin A (IgA) is commonly recognized as the most prevalent antibody (Ab) at mucosal sites with an important role in defense by shielding mucosal surfaces from invasion by pathogens. However, its potential to both actively dampen excessive immune responses or to initiate potent proinflammatory cellular processes is less well known. Interestingly, either functional outcome is mediated through interaction with the myeloid IgA Fc receptor FcαRI (CD89). Monomeric interaction of IgA with FcαRI triggers inhibitory signals that block activation via other receptors, whereas multimeric FcαRI crosslinking induces phagocytosis, reactive oxygen species production, antigen presentation, Ab-dependent cellular cytotoxicity, and cytokine release. Thus, FcαRI acts as a regulator between anti- and proinflammatory responses of IgA. As such, the biology of FcαRI, and its multifaceted role in immunity will be the focus of this review.

Do regulatory antibodies offer an alternative mechanism to explain the hygiene hypothesis?

The 'hygiene hypothesis', or lack of microbial and parasite exposure during early life, is postulated as an explanation for the recent increase in autoimmune and allergic diseases in developed countries. The favored mechanism is that microbial and parasite-derived products interact directly with pathogen recognition receptors to subvert proinflammatory signaling via T regulatory cells, thereby inducing anti-inflammatory effects and control of autoimmune disease. Parasites, such as helminths, are considered to have a major role in the induction of immune regulatory mechanisms among children living in developing countries. Invoking Occam's razor, we believe we can select an alternative mechanism to explain the hygiene hypothesis, based on antibody-mediated inhibition of immune responses that may more simply explain the available evidence.

Immunoglobulin A: A next generation of therapeutic antibodies?

Although immunoglobulin (Ig) A is commonly recognized as the most prevalent antibody subclass at mucosal sites with an important role in mucosal defense, its potential as a therapeutic monoclonal antibody is less well known. However, IgA has multifaceted anti-, non-, and pro-inflammatory functions that can be exploited for different immunotherapeutical strategies, which will be the focus of this review.

Henoch-Schonlein purpura nephritis: pathophysiology, treatment, and future strategy

Henoch-Schönlein purpura nephritis is a rare kidney disease leading to chronic kidney disease in a non-negligible percentage of patients. Although retrospective studies suggest beneficial effects of some therapies, prospective randomized clinical trials proving treatment efficacy are still lacking. The dilemma of spontaneous recovery even in patients with severe clinical and histologic presentation and of late evolution to chronic kidney disease in patients with mild initial symptoms renders it difficult for clinicians to expose patients to treatment protocols that are not evidence-based. A better understanding of the pathophysiology of progression to chronic kidney disease in Henoch-Schönlein purpura patients could be achieved by designing prospective international multicenter studies looking at determinants of clinical and histopathological evolution as well as possible circulating and urinary markers of progression. Such studies should be supported by a database available on the web and a new histologic classification of kidney lesions. This paper reports clinical, pathologic, and experimental data to be used for this strategy and to assist clinicians and clinical trial designers to reach therapeutic decisions.