IgA receptors in health and disease

Evaluation of Immune Response to Mucosal Immunization with an Oral Probiotic-Based Vaccine in Mice: Potential for Prime-Boost Immunization against SARS-CoV-2

Following the conclusion of the COVID-19 pandemic, the persistent genetic variability in the virus and its ongoing circulation within the global population necessitate the enhancement of existing preventive vaccines and the development of novel ones. A while back, we engineered an orally administered probiotic-based vaccine, L3-SARS, by integrating a gene fragment that encodes the spike protein S of the SARS-CoV-2 virus into the genome of the probiotic strain E. faecium L3, inducing the expression of viral antigen on the surface of bacteria. Previous studies demonstrated the efficacy of this vaccine candidate in providing protection against the virus in Syrian hamsters. In this present study, utilizing laboratory mice, we assess the immune response subsequent to immunization via the gastrointestinal mucosa and discuss its potential as an initial phase in a two-stage vaccination strategy. Our findings indicate that the oral administration of L3-SARS elicits an adaptive immune response in mice. Pre-immunization with L3-SARS enhances and prolongs the humoral immune response following a single subcutaneous immunization with a recombinant S-protein analogous to the S-insert of the coronavirus in Enterococcus faecium L3.

Exploring Immunome and Microbiome Interplay in Reproductive Health: Current Knowledge, Challenges, and Novel Diagnostic Tools

The dynamic interplay between the immunome and microbiome in reproductive health is a complex and rapidly advancing research field, holding tremendously vast possibilities for the development of reproductive medicine. This immunome-microbiome relationship influences the innate and adaptive immune responses, thereby affecting the onset and progression of reproductive disorders. However, the mechanisms governing these interactions remain elusive and require innovative approaches to gather more understanding. This comprehensive review examines the current knowledge on reproductive microbiomes across various parts of female reproductive tract, with special consideration of bidirectional interactions between microbiomes and the immune system. Additionally, it explores innate and adaptive immunity, focusing on immunoglobulin (Ig) A and IgM antibodies, their regulation, self-antigen tolerance mechanisms, and their roles in immune homeostasis. This review also highlights ongoing technological innovations in microbiota research, emphasizing the need for standardized detection and analysis methods. For instance, we evaluate the clinical utility of innovative technologies such as Phage ImmunoPrecipitation Sequencing (PhIP-Seq) and Microbial Flow Cytometry coupled to Next-Generation Sequencing (mFLOW-Seq). Despite ongoing advancements, we emphasize the need for further exploration in this field, as a deeper understanding of immunome-microbiome interactions holds promise for innovative diagnostic and therapeutic strategies for reproductive health, like infertility treatment and management of pregnancy.

Comparative proteomic analysis of glomerular proteins in IgA nephropathy and IgA vasculitis with nephritis

BACKGROUND

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN) are related glomerular diseases characterized by marked similarities in immunological and histological findings. We herein performed a comparative proteomic analysis of glomerular proteins in IgAN and IgAVN.

METHODS

We used renal biopsy specimens from 6 IgAN patients without nephrotic syndrome (NS) (IgAN-I subgroup), 6 IgAN patients with NS (IgAN-II subgroup), 6 IgAVN patients with 0-8.0% of glomeruli with crescent formation (IgAVN-I subgroup), 6 IgAVN patients with 21.2-44.8% of glomeruli with crescent formation (IgAVN-II subgroup), 9 IgAVN patients without NS (IgAVN-III subgroup), 3 IgAVN patients with NS (IgAN-IV subgroup), and 5 control cases. Proteins were extracted from laser microdissected glomeruli and analyzed using mass spectrometry. The relative abundance of proteins was compared between groups. An immunohistochemical validation study was also performed.

RESULTS

More than 850 proteins with high confidence were identified. A principal component analysis revealed a clear separation between IgAN and IgAVN patients and control cases. In further analyses, 546 proteins that were matched with ≥ 2 peptides were selected. The levels of immunoglobulins (IgA, IgG, and IgM), complements (C3, C4A, C5, and C9), complement factor H-related proteins (CFHR) 1 and 5, vitronectin, fibrinogen chains, and transforming growth factor-β inducible gene-h3 were higher (> 2.6 fold) in the IgAN and IgAVN subgroups than in the control group, whereas hornerin levels were lower (< 0.3 fold). Furthermore, C9 and CFHR1 levels were significantly higher in the IgAN group than in the IgAVN group. The abundance of some podocyte-associated proteins and glomerular basement membrane (GBM) proteins was significantly less in the IgAN-II subgroup than in the IgAN-I subgroup as well as in the IgAVN-IV subgroup than in the IgAVN-III subgroup. Among the IgAN and IgAVN subgroups, talin 1 was not detected in the IgAN-II subgroup. This result was supported by immunohistochemical findings.

CONCLUSIONS

The present results suggest shared molecular mechanisms for glomerular injury in IgAN and IgAVN, except for enhanced glomerular complement activation in IgAN. Differences in the protein abundance of podocyte-associated and GBM proteins between IgAN and IgAVN patients with and without NS may be associated with the severity of proteinuria.

Persistent but dysfunctional mucosal SARS-CoV-2-specific IgA and low lung IL-1β associate with COVID-19 fatal outcome: A cross-sectional analysis

The role of the mucosal pulmonary antibody response in coronavirus disease 2019 (COVID-19) outcome remains unclear. Here, we found that in bronchoalveolar lavage (BAL) samples from 48 patients with severe COVID-19-infected with the ancestral Wuhan virus, mucosal IgG and IgA specific for S1, receptor-binding domain (RBD), S2, and nucleocapsid protein (NP) emerged in BAL containing viruses early in infection and persist after virus elimination, with more IgA than IgG for all antigens tested. Furthermore, spike-IgA and spike-IgG immune complexes were detected in BAL, especially when the lung virus has been cleared. BAL IgG and IgA recognized the four main RBD variants. BAL neutralizing titers were higher early in COVID-19 when virus replicates in the lung than later in infection after viral clearance. Patients with fatal COVID-19, in contrast to survivors, developed higher levels of mucosal spike-specific IgA than IgG but lost neutralizing activities over time and had reduced IL-1β in the lung. Altogether, mucosal spike and NP-specific IgG and S1-specific IgA persisting after lung severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) clearance and low pulmonary IL-1β correlate with COVID-19 fatal outcome. Thus, mucosal SARS-CoV-2-specific antibodies may have adverse functions in addition to protective neutralization.

Variable-heavy (VH) families influencing IgA1&2 engagement to the antigen, FcαRI and superantigen proteins G, A, and L

Interest in IgA as an alternative antibody format has increased over the years with much remaining to be investigated in relation to interactions with immune cells. Considering the recent whole antibody investigations showing significant distal effects between the variable (V) and constant (C)- regions that can be mitigated by the hinge regions of both human IgA subtypes A1 and A2, we performed an in-depth mechanistic investigation using a panel of 28 IgA1s and A2s of both Trastuzumab and Pertuzumab models. FcαRI binding were found to be mitigated by the differing glycosylation patterns in IgA1 and 2 with contributions from the CDRs. On their interactions with antigen-Her2 and superantigens PpL, SpG and SpA, PpL was found to sterically hinder Her2 antigen binding with unexpected findings of IgAs binding SpG at the CH2-3 region alongside SpA interacting with IgAs at the CH1. Although the VH3 framework (FWR) is commonly used in CDR grafting, we found the VH1 framework (FWR) to be a possible alternative when grafting IgA1 and 2 owing to its stronger binding to antigen Her2 and weaker interactions to superantigen Protein L and A. These findings lay the foundation to understanding the interactions between IgAs and microbial superantigens, and also guide the engineering of IgAs for future antibody applications and targeting of superantigen-producing microbes.

α1-Antitrypsin attenuates acute rejection of orthotopic murine lung allografts

Background

α1-Antitrypsin (AAT) is an acute phase glycoprotein, a multifunctional protein with proteinase inhibitory, anti-inflammatory and cytoprotective properties. Both preclinical and clinical experiences show that the therapy with plasma purified AAT is beneficial for a broad spectrum of inflammatory conditions. The potential effects of AAT therapy have recently been highlighted in lung transplantation (LuTx) as well.

Methods

We used a murine fully mismatched orthotopic single LuTx model (BALB/CJ as donors and C57BL/6 as recipients). Human AAT preparations (5 mg, n = 10) or vehicle (n = 5) were injected to the recipients subcutaneously prior to and intraperitoneally immediately after the LuTx. No immune suppressive drugs were administered. Three days after the transplantation, the mice were sacrificed, and biological samples were assessed.

Results

Histological analysis revealed significantly more severe acute rejection in the transplanted lungs of controls than in AAT treated mice (p < 0.05). The proportion of neutrophil granulocytes, B cells and the total T helper cell populations did not differ between two groups. There was no significant difference in serum CXCL1 (KC) levels. However, when compared to controls, human AAT was detectable in the serum of mice treated with AAT and these mice had a higher serum anti-elastase activity, and significantly lower proportion of Th1 and Th17 among all Th cells. Cleaved caspase-3-positive cells were scarce but significantly less abundant in allografts from recipients treated with AAT as compared to those treated with vehicle.

Conclusion

Therapy with AAT suppresses the acute rejection after LuTx in a mouse model. The beneficial effects seem to involve anti-protease and immunomodulatory activities of AAT.

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.

Innate Mechanisms in Selective IgA Deficiency

Selective IgA deficiency (SIgAD), characterized by a serum IgA level below 0.07 mg/ml, while displaying normal serum levels of IgM and IgG antibodies, is the most frequently occurring primary immunodeficiency that reveals itself after the first four years after birth. These individuals with SIgAD are for the majority healthy and even when they are identified they are usually not investigated further or followed up. However, recent studies show that newborns and young infants already display clinical manifestations of this condition due to aberrancies in their immune defense. Interestingly, there is a huge heterogeneity in the clinical symptoms of the affected individuals. More than 50% of the affected individuals do not have clinical symptoms, while the individuals that do show clinical symptoms can suffer from mild to severe infections, allergies and autoimmune diseases. However, the reason for this heterogeneity in the manifestation of clinical symptoms of the individuals with SIgAD is unknown. Therefore, this review focusses on the characteristics of innate immune system driving T-cell independent IgA production and providing a mechanism underlying the development of SIgAD. Thereby, we focus on some important genes, including TNFRSF13B (encoding TACI), associated with SIgAD and the involvement of epigenetics, which will cover the methylation degree of TNFRSF13B, and environmental factors, including the gut microbiota, in the development of SIgAD. Currently, no specific treatment for SIgAD exists and novel therapeutic strategies could be developed based on the discussed information.

Efficient production of recombinant secretory IgA against Clostridium difficile toxins in CHO-K1 cells

Despite the essential role secretory IgAs play in the defense against pathogenic invasion and the proposed value of recombinant secretory IgAs as novel therapeutics, currently there are no IgA-based therapies in clinics. Secretory IgAs are complex molecules and the major bottleneck limiting their therapeutic potential is a reliable recombinant production system. In this report, we addressed this issue and established a fast and robust production method for secretory IgAs in CHO-K1 cells using BAC-based expression vectors. As a proof of principle, we produced IgAs against Clostridium difficile toxins TcdA and TcdB. Recombinant secretory IgAs produced using our expression system showed comparable titers to IgGs, widely used as therapeutic biologicals. Importantly, secretory IgAs produced using our method were functional and could efficiently neutralize Clostridium difficile toxins TcdA and TcdB. These results show that recombinant secretory IgAs can be efficiently produced, thus opening the possibility to use them as therapeutic agents in clinics.

More Than Just a Barrier: The Immune Functions of the Airway Epithelium in Asthma Pathogenesis

Allergic bronchial asthma is a chronic disease of the airways that is characterized by symptoms like respiratory distress, chest tightness, wheezing, productive cough, and acute episodes of broncho-obstruction. This symptom-complex arises on the basis of chronic allergic inflammation of the airway wall. Consequently, the airway epithelium is central to the pathogenesis of this disease, because its multiple abilities directly have an impact on the inflammatory response and thus the formation of the disease. In turn, its structure and functions are markedly impaired by the inflammation. Hence, the airway epithelium represents a sealed, self-cleaning barrier, that prohibits penetration of inhaled allergens, pathogens, and other noxious agents into the body. This barrier is covered with mucus that further contains antimicrobial peptides and antibodies that are either produced or specifically transported by the airway epithelium in order to trap these particles and to remove them from the body by a process called mucociliary clearance. Once this first line of defense of the lung is overcome, airway epithelial cells are the first cells to get in contact with pathogens, to be damaged or infected. Therefore, these cells release a plethora of chemokines and cytokines that not only induce an acute inflammatory reaction but also have an impact on the alignment of the following immune reaction. In case of asthma, all these functions are impaired by the already existing allergic immune response that per se weakens the barrier integrity and self-cleaning abilities of the airway epithelium making it more vulnerable to penetration of allergens as well as of infection by bacteria and viruses. Recent studies indicate that the history of allergy- and pathogen-derived insults can leave some kind of memory in these cells that can be described as imprinting or trained immunity. Thus, the airway epithelium is in the center of processes that lead to formation, progression and acute exacerbation of asthma.

Local eosinophils are associated with increased IgA subclass levels in the sinonasal mucosa of chronic rhinosinusitis with polyp patients

Background

Chronic rhinosinusitis (CRS) describes an inflammatory condition affecting the sinonasal mucosa. As the immune system players such as immunoglobulins play prominent roles in the development of CRS, we aimed to investigate the expression of IgA subclasses and factors involved in IgA class switching in the sinonasal mucosa of CRS patients.

Methods

Specimens were collected from the sinonasal mucosa of the healthy controls and CRS patients. Histological assessments were performed by H&E and immunohistochemistry. Real-time PCR and ELISA methods were applied to measure gene expression and protein levels extracted from tissue samples, respectively.

Results

We observed that total IgA and subclass-positive cells were higher in the patient groups than controls. There was a significant correlation between the number of eosinophils and total IgA and subclasses-positive cells (Pv < 0.0001). The expression of CXCL13, BAFF, AID, and germline transcripts were increased in CRSwNP patients. In contrast to IgA2 levels, IgA1 levels were significantly increased in the sinonasal tissue of CRSwNP patients (Pv < 0.01). TGF-β was significantly elevated in the sinonasal tissue of patients with CRSsNP.

Conclusions

Increased protein levels of IgA subclasses and related antibody-producing cells were associated with elevated eosinophils in CRSwNP patients which may result in eosinophil pathological functions. Several therapeutic approaches might be developed to modulate the IgA production to ameliorate the inflammatory mechanisms in CRSwNP patients.

Repeated-oral dose toxicity of polyethylene microplastics and the possible implications on reproduction and development of the next generation

With the increased distribution of microplastics in the environment, the potential for harmful effects on human health and ecosystems have become a global concern. Considering that polyethylene microplastics (PE-MPs) are among the most produced plastics worldwide, we administered PE-MPs (0.125, 0.5, 2 mg/day/mouse) by gavage to mice (10 mice/sex/dose) for 90 days. Compared to control, the body weight gain was significantly reduced in the male mice, and the proportion of neutrophils in the blood stream clearly increased in both sexes of mice. Persistence of a PE-MPs-like material and migration of granules to the mast cell membrane and accumulation of damaged organelles were observed in the stomachs and the spleens from the treated dams, respectively. Additionally, the IgA level in the blood stream was significantly elevated in the dams administered with PE-MPs compared to control, and the subpopulation of lymphocytes within the spleen was altered. Following, we performed an additional study to screen the effects of PE-MPs on reproduction and development (5 mice/sex/dose). Importantly, number of live births per dam, the sex ratio of pups, and body weight of pups was notably altered in groups treated with PE-MPs compared to the control group. Additionally, PE-MPs affected the subpopulation of lymphocytes within the spleen of the offspring, as did in the dams. Therefore, we propose that reproductive and developmental toxicity testing is warranted to evaluate the safety of microplastics. Additionally, we suggest that the IgA level may be used as a biomarker for harmful effects following exposure on microplastics.

IgA and FcαRI: Pathological Roles and Therapeutic Opportunities

Immunoglobulin A (IgA) is the most abundant antibody class present at mucosal surfaces. The production of IgA exceeds the production of all other antibodies combined, supporting its prominent role in host-pathogen defense. IgA closely interacts with the intestinal microbiota to enhance its diversity, and IgA has a passive protective role via immune exclusion. Additionally, inhibitory ITAMi signaling via the IgA Fc receptor (FcαRI; CD89) by monomeric IgA may play a role in maintaining homeostatic conditions. By contrast, IgA immune complexes (e.g., opsonized pathogens) potently activate immune cells via cross-linking FcαRI, thereby inducing pro-inflammatory responses resulting in elimination of pathogens. The importance of IgA in removal of pathogens is emphasized by the fact that several pathogens developed mechanisms to break down IgA or evade FcαRI-mediated activation of immune cells. Augmented or aberrant presence of IgA immune complexes can result in excessive neutrophil activation, potentially leading to severe tissue damage in multiple inflammatory, or autoimmune diseases. Influencing IgA or FcαRI-mediated functions therefore provides several therapeutic possibilities. On the one hand (passive) IgA vaccination strategies can be developed for protection against infections. Furthermore, IgA monoclonal antibodies that are directed against tumor antigens may be effective as cancer treatment. On the other hand, induction of ITAMi signaling via FcαRI may reduce allergy or inflammation, whereas blocking FcαRI with monoclonal antibodies, or peptides may resolve IgA-induced tissue damage. In this review both (patho)physiological roles as well as therapeutic possibilities of the IgA-FcαRI axis are addressed.

Phospholipid transfer protein and alpha-1 antitrypsin regulate Hck kinase activity during neutrophil degranulation

Excessive neutrophil degranulation is a common feature of many inflammatory disorders, including alpha-1 antitrypsin (AAT) deficiency. Our group has demonstrated that phospholipid transfer protein (PLTP) prevents neutrophil degranulation but serine proteases, which AAT inhibits, cleave PLTP in diseased airways. We propose to identify if airway PLTP activity can be restored by AAT augmentation therapy and how PLTP subdues degranulation of neutrophils in AAT deficient subjects. Airway PLTP activity was lower in AAT deficient patients but elevated in the airways of patients on augmentation therapy. Functional AAT protein (from PiMM homozygotes) prevented PLTP cleavage unlike its mutated ZZ variant (PiZZ). PLTP lowered leukotriene B4 induced degranulation of primary, secondary and tertiary granules from neutrophils from both groups (n = 14/group). Neutrophils isolated from Pltp knockout mice have enhance neutrophil degranulation. Both AAT and PLTP reduced neutrophil degranulation and superoxide production, possibly though their inhibition of the Src tyrosine kinase, Hck. Src kinase inhibitors saracatinib and dasatinib reduced neutrophil degranulation and superoxide production. Therefore, AAT protects PLTP from proteolytic cleavage and both AAT and PLTP mediate degranulation, possibly via Hck tyrosine kinase inhibition. Deficiency of AAT could contribute to reduced lung PLTP activity and elevated neutrophil signaling associated with lung disease.

A genome-wide trans-ethnic interaction study links the PIGR-FCAMR locus to coronary atherosclerosis via interactions between genetic variants and residential exposure to traffic

Air pollution is a worldwide contributor to cardiovascular disease mortality and morbidity. Traffic-related air pollution is a widespread environmental exposure and is associated with multiple cardiovascular outcomes such as coronary atherosclerosis, peripheral arterial disease, and myocardial infarction. Despite the recognition of the importance of both genetic and environmental exposures to the pathogenesis of cardiovascular disease, studies of how these two contributors operate jointly are rare. We performed a genome-wide interaction study (GWIS) to examine gene-traffic exposure interactions associated with coronary atherosclerosis. Using race-stratified cohorts of 538 African-Americans (AA) and 1562 European-Americans (EA) from a cardiac catheterization cohort (CATHGEN), we identify gene-by-traffic exposure interactions associated with the number of significantly diseased coronary vessels as a measure of chronic atherosclerosis. We found five suggestive (P<1x10^-5) interactions in the AA GWIS, of which two (rs1856746 and rs2791713) replicated in the EA cohort (P < 0.05). Both SNPs are in the PIGR-FCAMR locus and are eQTLs in lymphocytes. The protein products of both PIGR and FCAMR are implicated in inflammatory processes. In the EA GWIS, there were three suggestive interactions; none of these replicated in the AA GWIS. All three were intergenic; the most significant interaction was in a regulatory region associated with SAMSN1, a gene previously associated with atherosclerosis and B cell activation. In conclusion, we have uncovered several novel genes associated with coronary atherosclerosis in individuals chronically exposed to increased ambient concentrations of traffic air pollution. These genes point towards inflammatory pathways that may modify the effects of air pollution on cardiovascular disease risk.

The long and winding road to IgA deficiency: causes and consequences

INTRODUCTION

The most common humoral immunodeficiency is IgA deficiency. One of the first papers addressing the cellular and molecular mechanisms underlying IgA deficiency indicated that immature IgA-positive B-lymphocytes are present in these patients. This suggests that the genetic background for IgA is still intact and that class switching can take place. At this moment, it cannot be ruled out that genetic as well as environmental factors are involved. Areas covered: A clinical presentation, the biological functions of IgA, and the management of IgA deficiency are reviewed. In some IgA deficient patients, a relationship with a loss-of-function mutation in the TACI (transmembrane activator and calcium-modulating cyclophilin ligand interaction) gene has been found. Many other genes also have been associated. Gut microbiota are an important environmental trigger for IgA synthesis. Expert commentary: Expression of IgA deficiency is due to both genetic and environmental factors and a role for gut microbiota cannot be excluded.

Morphological and immunohistochemical analyses of soluble proteins in mucous membranes of living mouse intestines by cryotechniques

We have performed immunohistochemical or ultrastructural analyses of living mouse small intestines using Epon blocks prepared by 'in vivo cryotechnique' (IVCT). By electron microscopy, intracellular ultrastructures of epithelial cells were well preserved in tissue areas 5-10 μm away from cryogen-contact surface tissues. Their microvilli contained dynamically waving actin filaments, and highly electron-dense organelles, such as mitochondria, were seen under the widely organized terminal web. By quick-freezing of fresh resected tissues (FT-QF), many erythrocytes were congested within blood vessels due to loss of blood pressure. By immersion-fixation (IM-DH) and perfusion-fixation (PF-DH), small vacuoles were often seen in the cytoplasm of epithelial cells, and their intercellular spaces were also dilated. Moreover, actin filament bundles were irregular in cross sections of microvilli, compared with those with IVCT. Epon-embedded thick sections were treated with sodium ethoxide, followed by antigen retrieval and immunostained for immunoglobulin A (IgA), Ig kappa light chain (Igκ), J-chain and albumin. By cryotechniques, IgA immunoreactivity was detected as tiny dot-like patterns in cytoplasm of some epithelial cells. Both J-chain and Igκ immunoreactivities were detected in the same local areas as those of IgA. By FT-QF, however, the IgA immunoreactivity was more weakly detected, compared with that with IVCT. In thick sections prepared by IM-DH and PF-DH, it was rarely observed in both plasma and epithelial cells. Another albumin was diffusely immunolocalized in extracellular matrices of mucous membranes and also within blood vessels. Thus, IVCT was useful for preservation of soluble proteins and ultrastructural analyses of dynamically changing epithelial cells of living mouse small intestines.

Identification of plasma protein markers common to patients with malignant tumour and Abnormal Savda in Uighur medicine: a prospective clinical study

Background

Traditional Uighur medicine shares an origin with Greco-Arab medicine. It describes the health of a human body as the dynamic homeostasis of four normal Hilits (humours), known as Kan, Phlegm, Safra, and Savda. An abnormal change in one Hilit may cause imbalance among the Hilits, leading to the development of a syndrome. Abnormal Savda is a major syndrome of complex diseases that are associated with common biological changes during disease development. Here, we studied the protein expression profile common to tumour patients with Abnormal Savda to elucidate the biological basis of this syndrome and identify potential biomarkers associated with Abnormal Savda.

Methods

Patients with malignant tumours were classified by the diagnosis of Uighur medicine into two groups: Abnormal Savda type tumour (ASt) and non-Abnormal Savda type tumour (nASt), which includes other syndromes. The profile of proteins that were differentially expressed in ASt compared with nASt and normal controls (NC) was analysed by iTRAQ proteomics and evaluated by bioinformatics using MetaCore™ software and an online database. The expression of candidate proteins was verified in all plasma samples by enzyme-linked immunosorbent assay (ELISA).

Results

We identified 31 plasma proteins that were differentially expressed in ASt compared with nASt, of which only 10 showed quantitatively different expression between ASt and NC. Bioinformatics analysis indicated that most of these proteins are known biomarkers for neoplasms of the stomach, breast, and lung. ELISA detection showed significant upregulation of plasma SAA1 and SPP24 and downregulation of PIGR and FASN in ASt compared with nASt and NC (p < 0.05).

Conclusions

Abnormal Savda may be causally associated with changes in the whole regulation network of protein expression during carcinogenesis. The expression of potential biomarkers might be used to distinguish Abnormal Savda from other syndromes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-015-0526-6) contains supplementary material, which is available to authorized users.

Role of secretory IgA in the mucosal sensing of commensal bacteria

While the gut epithelium represents the largest mucosal tissue, the mechanisms underlying the interaction between intestinal bacteria and the host epithelium lead to multiple outcomes that remain poorly understood at the molecular level. Deciphering such events may provide valuable information as to the mode of action of commensal and probiotic microorganisms in the gastrointestinal environment. Potential roles of such microorganisms along the privileged target represented by the intestinal immune system include maturation processes prior, during and after weaning, and the reduction of inflammatory reactions in pathogenic conditions. As commensal bacteria are naturally coated by natural and antigen-specific SIgA in the gut lumen, understanding the consequences of such an interaction may provide new clues on how the antibody contributes to homeostasis at mucosal surfaces. This review discusses several aspects of the role of SIgA in the essential communication existing between the host epithelium and members of its microbiota.

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.

Effect of a tail piece cysteine deletion on biochemical and functional properties of an epidermal growth factor receptor-directed IgA2m(1) antibody

Antibodies of human IgA isotype are critical components of the mucosal immune system, but little is known about their immunotherapeutic potential. Compared with IgG antibodies, IgA molecules carry a C-terminal tail piece extension of 18 amino acids with a free cysteine at position 471. This cysteine is required for the formation of dimeric IgA antibodies, but may impair molecular characteristics of monomeric IgA antibodies as therapeutic reagents. Thus, we generated and characterized a d471-mutated antibody against the epidermal growth factor receptor (EGFR) and compared it to its respective IgA2m(1) wild type antibody. Both wild type and mutated IgA antibodies demonstrated similar EGFR binding and were similarly efficient in inhibiting EGF binding and in blocking EGF-mediated cell proliferation. Recruitment of Fc-mediated effector functions like antibody-dependent cell-mediated cytotoxicity by monocytes, macrophages or PMN was similar, but the d471-mutated IgA exhibited different biochemical properties compared with wild type antibody. As expected, mutated IgA did not form stable dimers in the presence of human joining (J)-chain, but we also observed reduced levels of dimeric aggregates in the absence of J-chain. Furthermore, glycoprofiling revealed different glycosylation patterns for both antibodies, including considerably less mannosylation of d471-mutated antibodies. Overall, our results demonstrate that the deletion of the C-terminal cysteine of IgA2 did not affect the investigated effector functions compared with wild type antibody, but it improved biochemical properties of an IgA2m(1) antibody against EGFR, and may thereby assist in exploring the immunotherapeutic potential of recombinant IgA antibodies.

Fc receptor-mediated immune responses: new tools but increased complexity in HIV prevention

The modest success of the RV144 HIV vaccine trial in Thailand and the ensuing suggestion that a Fc-receptormediated antibody activity might have played a role in the protection observed have intensified investigations on Fcrelated immune responses. HIV neutralizing antibodies have been and continue to be the focal point of research into humoral immune protection. However, recent knowledge that their protective efficacy can be augmented by Fc-FcR interactions has increased the complexity of identifying immune correlates of protection. If anything, continued studies of both humoral and cellular immune mechanisms point to the lack of a single protective anti-HIV immune response. Here we focus on humoral immunity, analyzing the role played by Fc receptor-related responses and discussing how new knowledge of their interactions requires further investigation, but may also spur novel vaccination approaches. We initially address classical Fc-receptor mediated anti-viral mechanisms including antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cell mediated viral inhibition (ADCVI), and antibody-dependent cellular phagocytosis (ADCP), as well as the effector cells that mediate these functions. Next, we summarize key aspects of FcR-Fc interactions that are important for potential control of HIV/SIV such as FcR polymorphisms and post-transcriptional modifications. Finally we discuss less commonly studied non-mechanistic anti-HIV immune functions: antibody avidity and envelopespecific B cell memory. Overall, a spectrum of immune responses, reflecting the immune system's redundancy, will likely be needed to prevent HIV infection and/or disease progression. Aside from elicitation of critical immune mechanisms, a successful vaccine will need to induce mature B cell responses and long-lasting immune memory.

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.

Serum extracellular vesicle protein levels are associated with acute coronary syndrome

AIMS

Biomarkers are essential in the early detection of acute coronary syndromes (ACS). Serum extracellular vesicles are small vesicles in the plasma containing protein and RNA and have been shown to be involved in ACS-related processes like apoptosis and coagulation. Therefore, we hypothesized that serum extracellular vesicle protein levels are associated with ACS.

METHODS AND RESULTS

Three serum extracellular vesicle proteins potentially associated with ACS were identified with differential Q-proteomics and were evaluated in 471 frozen serum samples of ACS-suspected patients presenting to the emergency department (30% of whom had an ACS). Protein levels were measured after vesicle isolation using ExoQuick. Mean serum extracellular vesicle concentration of the different proteins was compared between ACS and non-ACS patients. Selected proteins were tested in a univariate logistic regression model, as well as in a multivariate model to adjust for cardiovascular risk factors. A separate analysis was performed in men and women. In the multivariate logistic regression analysis, polygenic immunoglobulin receptor, (pIgR; OR 1.630, p=0.026), cystatin C (OR 1.641, p=0.021), and complement factor C5a (C5a, OR 1.495, p=0.025) were significantly associated with ACS, while total vesicle protein concentration was borderline significant. The association of the individual proteins with ACS was markedly stronger in men.

CONCLUSIONS

These data show that serum extracellular vesicle pIgR, cystatin C, and C5a concentrations are independently associated with ACS and that there are pronounced gender differences. These observations should be validated in a large, prospective study to assess the potential role of vesicle content in the evaluation of patients suspected of having an ACS.

Intravenous immunoglobulin in the management of lupus nephritis

The occurrence of nephritis in patients with systemic lupus erythematosus is associated with increased morbidity and mortality. The pathogenesis of lupus nephritis is complex, involving innate and adaptive cellular and humoral immune responses. Autoantibodies in particular have been shown to be critical in the initiation and progression of renal injury, via interactions with both Fc-receptors and complement. One approach in the management of patients with lupus nephritis has been the use of intravenous immunoglobulin. This therapy has shown benefit in the setting of many forms of autoantibody-mediated injury; however, the mechanisms of efficacy are not fully understood. In this paper, the data supporting the use of immunoglobulin therapy in lupus nephritis will be evaluated. In addition, the potential mechanisms of action will be discussed with respect to the known involvement of complement and Fc-receptors in the kidney parenchyma. Results are provocative and warrant additional clinical trials.

Blocking Fcα receptor I on granulocytes prevents tissue damage induced by IgA autoantibodies

IgA represents the most prominent Ab class at mucosal surfaces and the second most prevalent Ab in human blood after IgG. We recently demonstrated that cross-linking of the granulocyte IgA FcR (FcαRI) by IgA induces a chemotactic-driven positive-feedback migration loop, hereby amplifying recruitment of granulocytes to IgA deposits. Therefore, we postulated that aberrant IgA-Ag complexes, which can be found in tissues in IgA-mediated diseases, are responsible for tissue damage by inducing continuous granulocyte migration and activation. Using an IgA-dependent skin-blistering disease as a model system, we demonstrated colocalization of FcαRI-positive granulocyte infiltrates with IgA in cryosections of lesional skin of patients suffering from this disease. Furthermore, we showed granulocyte migration to IgA deposits injected in human skin explants and in murine skin of FcαRI transgenic mice in vivo. Importantly, ex vivo migration and tissue damage were inhibited by blocking FcαRI, indicating that these events are dependent on the interaction of IgA autoantibodies with FcαRI. Thus, interrupting the granulocyte migration loop by blocking FcαRI reduces tissue damage in diseases with aberrant IgA-immune complexes. As such, our results may lead to development of new therapies for IgA-mediated chronic inflammatory diseases, hereby decreasing severe morbidity and improving quality of life for these patients.

Colostrum of healthy mothers contains broad spectrum of secretory IgA autoantibodies

PURPOSE

Human colostrum and milk provide a newborn with immunomodulatory components, ensuring protection and proper development of the immune system. Secretory IgA antibodies in colostrum represent the first line of defence against harmful substances, but their potential spectra of reactivity with autoantigens remains unclear. Here, we characterised the repertoire of natural sectretory IgA autoantibodies in colostrum of healthy mothers.

METHODS

The human colostrum samples from 39 healthy mothers were analyzed for autoantibodies by indirect immunofluorescence, dot blots, immunoblots and ELISA.

RESULTS

We found that there is high diversity in reactivities of colostral IgA antibodies to autoantigens among individual samples. Using tissue sections and biochips commonly used for autoimmunity testing, we found that most samples reacted with monkey ovary (79.3%), monkey pancreatic tissue (78.6%), human HEp-2 cells (69%) and monkey adrenal gland (69.0%), fewer samples reacted with monkey liver tissue (47.2%), rat stomach (42.9%), monkey testicular tissue (41.4%), monkey salivary gland (39.3%), rat kidney (32.1%) and monkey cerebellar tissue (17.9%). At the protein level, we detected reactivity of IgA with 21 out of 25 (auto) antigens. The majority of the samples reacted with the pyruvate dehydrogenase complex, E3 ubiquitin ligase, cytosolic liver antigen, promyelocytic leukemia protein and nuclear pore glycoprotein-210. Using ELISA, we found reactivity of colostral IgA antibodies against examined extractable nuclear antigens, double stranded DNA, phospholipids and neutrophil cytoplasm.

CONCLUSIONS

The broad spectrum of polyreactive natural autoantibodies present in human colostrum may contribute to proper development of mucosal immune system of the breastfed infant.

Ratio of involved/uninvolved immunoglobulin quantification by Hevylite™ assay: clinical and prognostic impact in multiple myeloma

Background

HevyLite™ is a new, recently developed method that facilitates separate quantification of the kappa- and lambda-bounded amounts of a given immunoglobulin (Ig). Using this method, we measured intact immunoglobulin (heavy/light chain; HLC) IgG-kappa, IgG-lambda, IgA-kappa, IgA-lambda individually, as well as their deriving ratios (HLCR) in a series of IgG or IgA multiple myeloma (MM) patients, to investigate and assess the contribution of these tests to disease evaluation.

Patients and methods

HevyLite™ assays were used in sera from 130 healthy individuals (HI) and 103 MM patients, at time of diagnosis. In patients, the level of paraprotein was IgG in 78 (52 IgG-kappa, 26 IgG-lambda) and IgΑ in 25 (13 IgΑ-kappa, 12 IgΑ-lambda). Durie-Salmon and International Staging System stages were evenly distributed. Symptomatic patients (n = 77) received treatment while asymptomatic ones (n = 26) were followed. Patients' median follow-up was at 32.6 months. HLCR was calculated with the involved Ig (either G or A) as numerator.

Results

In HI, median IgG-kappa was 6.85, IgG-lambda 3.81, IgA-kappa 1.19 and IgA-lambda 0.98 g/L. The corresponding median involving HLC values in MM patients were 25.8, 23.45, 28.9 and 36.4 g/L. HLC-IgG related to anemia, high serum free light chain ratio and extensive bone marrow infiltration, while high HLCR correlated with the same plus increased β2-microglobulin. In addition, increased HLCR and the presence of immunoparesis correlated with time to treatment. Patients with high HLCR had a significantly shorter survival (p = 0.022); HLCR retained its prognostic value in multivariate analysis.

Conclusions

HLC and HLCR quantify the precise amount of the involved immunoglobulin more accurately than other methods; moreover, they carry prognostic information regarding survival in MM patients.

Salivary defense proteins: their network and role in innate and acquired oral immunity

There are numerous defense proteins present in the saliva. Although some of these molecules are present in rather low concentrations, their effects are additive and/or synergistic, resulting in an efficient molecular defense network of the oral cavity. Moreover, local concentrations of these proteins near the mucosal surfaces (mucosal transudate), periodontal sulcus (gingival crevicular fluid) and oral wounds and ulcers (transudate) may be much greater, and in many cases reinforced by immune and/or inflammatory reactions of the oral mucosa. Some defense proteins, like salivary immunoglobulins and salivary chaperokine HSP70/HSPAs (70 kDa heat shock proteins), are involved in both innate and acquired immunity. Cationic peptides and other defense proteins like lysozyme, bactericidal/permeability increasing protein (BPI), BPI-like proteins, PLUNC (palate lung and nasal epithelial clone) proteins, salivary amylase, cystatins, prolin-rich proteins, mucins, peroxidases, statherin and others are primarily responsible for innate immunity. In this paper, this complex system and function of the salivary defense proteins will be reviewed.

A conserved host and pathogen recognition site on immunoglobulins: structural and functional aspects

A common site in the constant region (Fc) of immunoglobulins is recognized by host receptors and is a frequent target of proteins expressed by pathogens. This site is located at the junction of two constant domains in the antibody heavy chains and produces a large shallow cavity formed by loops of the CH2 and CH3 domains in IgG and IgA (CH3 and CH4 domains in IgM). Crystal structures have been determined for complexes of IgG-Fc and IgA-Fc with a structurally diverse set of host, pathogen and in vitro selected ligands. While pathogen proteins may directly block interactions with the immunoglobulins thereby evading host immunity, it is likely that the same pathogen molecules also interact with other host factors to carry out their primary biological function. Herein we review the structural and functional aspects of host and pathogen molecular recognition of the common site on the Fc of immunoglobulins. We also propose that some pathogen proteins may promote virulence by affecting the bridging between innate and adaptive immunity.

Sputum proteomics identifies elevated PIGR levels in smokers and mild-to-moderate COPD

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality around the world. However, the exact mechanisms leading to COPD and its progression are still poorly understood. In this study, induced sputum was analyzed by cysteine-specific two-dimensional difference gel electrophoresis (2D-DIGE) coupled with mass spectrometry to identify proteins involved in COPD pathogenesis. The comparison of nonsmokers, smokers, and smokers with moderate COPD revealed 15 changed proteins with the majority, including polymeric immunoglobulin receptor (PIGR), being elevated in smokers and subjects with COPD. PIGR, which is involved in specific immune defense and inflammation, was further studied in sputum, lung tissue, and plasma by Western blot, immunohistochemistry/image analysis, and/or ELISA. Sputum PIGR was characterized as glycosylated secretory component (SC). Lung PIGR was significantly elevated in the bronchial and alveolar epithelium of smokers and further increased in the alveolar area in mild to moderate COPD. Plasma PIGR was elevated in smokers and smokers with COPD compared to nonsmokers with significant correlation to obstruction. In conclusion, new proteins in smoking-related chronic inflammation and COPD could be identified, with SC/PIGR being one of the most prominent not only in the lung but also in circulating blood.

Interaction of human, rat, and mouse immunoglobulin A (IgA) with Staphylococcal superantigen-like 7 (SSL7) decoy protein and leukocyte IgA receptor

Host survival depends on an effective immune system and pathogen survival on the effectiveness of immune evasion mechanisms. Staphylococcus aureus utilizes a number of molecules to modulate host immunity, including the SSL family of which SSL7 binds IgA and inhibits Fcα receptor I (FcαRI)-mediated function. Other Gram-positive bacterial pathogens produce IgA binding proteins, which, similar to SSL7, also bind the Fc at the CH2/CH3 interface (the junction between constant domains 2 and 3 of the heavy chain). The opposing activities of the host FcαRI-IgA receptor ligand pair and the pathogen decoy proteins select for host and pathogen variants, which exert stronger protection or evasion, respectively. Curiously, mouse but not rat IgA contains a putative N-linked glycosylation site in the center of this host receptor and pathogen-binding site. Here, we demonstrate that this site is glycosylated and that the effect of amino acid changes and glycosylation of the CH2/CH3 interface inhibits interaction with the pathogen IgA binding protein SSL7, while maintaining binding of pIgR, essential to the biosynthesis and transport of SIgA.

Autoimmunity-driven enzymatic remodeling of the dermal-epidermal junction in bullous pemphigoid and dermatitis herpetiformis

Pathogenesis of blister formation in bullous pemphigoid (BP) and dermatitis herpetiformis (DH) is associated with destruction of numerous components of the dermal--epidermal junction. Proteolytic enzymes (PE) are involved in a multitude of physiological reactions and may have impact on the epidermal--dermal integrity. Involvement of various PE in inflammation and blister formation in BP and DH is intensively investigated using both morphologic and functional approaches, particularly in BP. The development into the full-blown stage in BP and DH may be caused by an impairment of the human Fc receptor regulatory system that may cause the inefficiently controlled activation of inflammatory cells and subsequent secretion of various proteases.

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.

Diabetes induced immunological and biochemical changes in human colostrum

AIM

This article describes the changes and relationships between biochemical and immunological parameters in the colostrum and serum of diabetic women.

METHODS

Colostrum and blood samples were collected from 30 diabetic and 15 normoglycaemic women. Glucose, total protein, antibody, complement proteins (C3 and C4), fat and calorie content, amylase, lipase and superoxide dismutase (SOD) were determined.

RESULTS

Glucose was higher in both the colostrum and serum of diabetic mothers compared to that of their normoglycaemic counterparts. In both groups, total protein was higher in colostrum than in serum. IgA and IgG were lower in the colostrum of hyperglycaemic mothers, whereas IgM did not vary between the groups. Colostral C3 protein was significantly lower in diabetic mothers, but colostral C4 protein was similar between normoglycaemic and hyperglycaemic mothers. Fat content was lower in the colostrum of the diabetic mothers, although calorie content did not vary between the groups. Amylase was lower in colostrum than in serum in both groups. Lipase was higher in the colostrum and serum of diabetic mothers. Colostral SOD was similar between the groups.

CONCLUSIONS

Our results support the hypothesis that the colostrum of diabetic mothers suffers biochemical and immunological alterations that affect the levels of its components.

Dysfunctions of the Iga system: a common link between intestinal and renal diseases

Immunoglobulin A (Iga)-isotype antibodies play an important role in immunity owing to their structure, glycosylation, localization and receptor interactions. Dysfunctions in this system can lead to multiple types of pathology. This review describes the characteristics of Iga and discusses the involvement of abnormalities in the Iga system on the development of celiac disease and Iga nephropathy.

The functional polymorphism 844 A>G in FcαRI (CD89) does not contribute to systemic sclerosis or rheumatoid arthritis susceptibility

OBJECTIVE

To investigate the role of the Fc(α)RI 844 A>G functional polymorphism in the genetic predisposition to rheumatoid arthritis (RA) and systemic sclerosis (SSc) susceptibility.

METHODS

The study population was composed of 1401 patients with SSc, 642 patients with RA, and 1317 healthy controls. The Fc(α)RI (CD89) single-nucleotide polymorphism rs16986050 was genotyped by pyrosequencing.

RESULTS

We observed no significant deviation of the genotype and allele frequencies in RA and SSc compared to controls. A metaanalysis and a recessive and dominant model yielded similar negative results.

CONCLUSION

Our data show that the Fc(α)RI 844 A>G polymorphism is not associated with SSc or RA susceptibility.

Immunohistochemical detection of soluble immunoglobulins in living mouse small intestines using an in vivo cryotechnique

Some morphological changes are inevitable during immersion- or perfusion-fixation and following alcohol-dehydration for tissue preparations. Common immunostaining techniques for these specimens have some limitations to capture accurate localizations of soluble proteins in cells and tissues. In this study, to examine in situ distributions of immunoglobulins (Igs), small intestinal tissues of living mice were prepared with our "in vivo cryotechnique" (IVCT). Thin sections were first stained with hematoxylin-eosin for morphology, and then some immunostainings were performed on serial sections for IgA, Ig kappa light chain, IgG1 heavy chain (IgG1), and IgM. Living morphological states of small intestinal tissues, including flowing erythrocytes and opening blood vessels, were observed on paraffin sections prepared with IVCT. IgA was immunolocalized in many plasma cells of the lamina mucosa propria, intestinal matrices, and also in epithelial cells of the intestinal villi and crypts. Both IgG1 and IgM immunoreactivities were mainly detected in blood vessels, whereas only IgG1 was also immunolocalized in interstitial matrices of mucous membranes. By perfusion-fixation and alcohol-dehydration, however, IgA immunoreactivity was observed in plasma cells, but not in epithelial cells or the lamina mucosa propria. Thus, IVCT was more useful to examine in vivo immunolocalizations of soluble Igs in small intestines.

Impact of human IgA antibodies on complement-dependent cytotoxicity mediated by combinations of EGF-R-directed antibodies

Dual combinations of non-crossblocking epidermal growth factor receptor (EGF-R)-directed monoclonal antibodies were demonstrated to effectively induce complement-dependent cytotoxicity (CDC) of tumor cells, whereas individual antibodies were ineffective. Here the modulating effects of different antibody isotypes on CDC were studied by adding them as a third antibody. Two different combinations of non-crossblocking EGF-R antibodies of human IgG1 isotype, 018/003 and 425/005, were investigated against the A431 and A1207 cell lines. As a third antibody, human IgG1, IgA1, and IgA2 isotype variants of the therapeutic EGF-R antibody 225 were employed that bind to an EGF-R epitope distinct from the other EGF-R antibodies. In this model, the human IgG1 antibody proved to further enhance CDC, whereas both IgA antibodies significantly blocked CDC. The IgG1 and IgA variants increased target opsonization at similar levels, but the isotypes differed in their effects on C1q fixation. Addition of IgG1 significantly enhanced complement factor binding on the target surface, whereas both IgA antibodies reduced complement binding. Control experiments revealed this blocking effect to be not specific to IgA antibodies, but to antibody constructs incapable of activating the complement system. Interestingly, the effects caused by the IgA2 isotype were consistently stronger than those by IgA1, which may be caused by stronger steric hindrance due to its reduced hinge flexibility. These results demonstrate that monoclonal IgA antibodies inhibit IgG-mediated complement activation in vitro and suggest that the appearance of IgA antibodies within a polyclonal immune response might inhibit complement activation in vivo.

Involvement of Fc receptors in disorders of the central nervous system

Immunoglobulins are proteins with a highly variable antigen-binding domain and a constant region (Fc domain) that binds to a cell surface receptor (FcR). Activation of FcRs in immune cells (lymphocytes, macrophages, and mast cells) triggers effector responses including cytokine production, phagocytosis, and degranulation. In addition to their roles in normal responses to infection or tissue injury, and in immune-related diseases, FcRs are increasingly recognized for their involvement in neurological disorders. One or more FcRs are expressed in microglia, astrocytes, oligodendrocytes, and neurons. Aberrant activation of FcRs in such neural cells may contribute to the pathogenesis of major neurodegenerative conditions including Alzheimer's disease, Parkinson's disease, ischemic stroke, and multiple sclerosis. On the other hand, FcRs may play beneficial roles in counteracting pathological processes; for e.g., FcRs may facilitate removal of amyloid peptides from the brain and so protect against Alzheimer's disease. Knowledge of the functions of FcRs in the nervous system in health and disease is leading to novel preventative and therapeutic strategies for stroke, Alzheimer's disease, and other neurological disorders.

Assessment of monoclonal gammopathies by nephelometric measurement of individual immunoglobulin kappa/lambda ratios

BACKGROUND

Currently, monoclonal immunoglobulins are identified and quantified from bands on electrophoretic gels. As an alternative, clonality might be determined by measuring the separate light chain types of each Ig class to allow numerical assessment of Ig'kappa/Ig'lambda ratios, analogous to free light chain kappa/lambda ratios.

METHODS

Using immunization, tolerization, and adsorption procedures, we prepared sheep antibodies against each of the 6 separate molecules, IgGkappa, IgGlambda, IgAkappa, IgAlambda, IgMkappa, and IgMlambda. Antibody targets comprised the junctional epitopes between the heavy chain and light chain domains. After purification, we assessed the antisera on a Siemens Dade-Behring BN II nephelometer for analytical quality and clinical utility.

RESULTS

High-avidity, specific antibodies allowed the production of automated nephelometric immunoassays for each Ig light chain type. Laboratory comparison with serum protein electrophoresis, using dilution experiments, showed lower analytical sensitivity for monoclonal IgG detection but similar or greater sensitivity for IgA and IgM, particularly when the monoclonal bands overlaid transferrin. Results obtained from typing of monoclonal proteins into IgG, A, or M types were comparable with results obtained by immunofixation-electrophoresis methods. Initial clinical studies, in multiple myeloma patients, indicated that Ig'kappa/Ig'lambda ratios were sometimes more sensitive than immunofixation electrophoresis, provided numerical results, and correlated with changes in disease.

CONCLUSIONS

Immunoassays for intact Ig kappa/lambda pairs are possible and should assist in the management of patients with monoclonal gammopathies.

A novel activating chicken IgY FcR is related to leukocyte receptor complex (LRC) genes but is located on a chromosomal region distinct from the LRC and FcR gene clusters

FcRs have multifaceted roles in the immune system. Chicken FcRs were demonstrated on macrophages decades ago; however, only recently the chicken Ig-like receptor AB1, encoded in the leukocyte receptor complex, was molecularly identified as a high-affinity FcR. The present study was initiated to identify additional receptors with the capability to bind chicken immunoglobulins. Based on database searches, we cloned a novel chicken FcR, designated gallus gallus FcR (ggFcR), which was shown to bind selectively chicken IgY. The receptor consists of four extracellular C2-set Ig domains, followed by a transmembrane region containing arginine as a positively charged amino acid and a short cytoplasmic tail. ggFcR associates with the common gamma-chain, indicative for an activating receptor, and real-time RT-PCR revealed high expression on PBMC, thrombocytes, and macrophages. The genomic organization is similar to most Ig-like receptor genes, where each Ig domain is encoded by a separate exon. Additionally, the ggFcR signal peptide is encoded by two exons, the second of which is 36 bp, a hallmark for genes encoded in the leukocyte receptor complex. Phylogenetic analysis also showed a relationship to genes encoded in the leukocyte receptor complex. Surprisingly, ggFcR is not encoded in the leukocyte receptor complex, but it is located as a single isolated gene at the extremity of chicken chromosome 20.

Fc receptors

The aggregation of cell surface Fc receptors by immune complexes induces a number of important antibody-dependent effector functions. It is becoming increasingly evident that the organization of key immune proteins has a significant impact on the function of these proteins. Comparatively little is known, however, about the nature of Fc receptor spatiotemporal organization. This review outlines the current literature concerning human Fc receptor spatial organization and physiological function.