Selective IgA Deficiency and Allergy: A Fresh Look to an Old Story

Role of mucosal IgA antibodies as novel therapies to enhance mucosal barriers

To prevent infection, the experience of the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) pandemic has led to recognition of the importance of not only vaccines but also the strengthening of mucosal barriers by secretory immunoglobulin A (IgA). Strong mucosal barrier provided by IgA is also possible to prevent allergies and chronic inflammatory conditions in the intestinal tract, since it can protect foreign enemies or antigens at the first line of defense before their invasion. Therefore, it is important to understand the role of IgA antibodies secreted by the mucosa of the body. In this section, we discuss the role of mucosal IgA antibodies in relation to three disease states: control of intestinal microbiota, protection against infection, and allergy. In addition, we provide the evidence in which the quality as well as the quantity of IgA is critical for disease prevention. Therefore, we discuss about novel strategies to enhance mucosal barriers by induction of high-quality IgA.

Limited Clinical Impact of Genetic Associations between Celiac Disease and Type 2 Inflammatory Diseases: Insights from Mendelian Randomization

Background: Celiac disease, a gluten-triggered autoimmune disorder, is known for its systemic inflammatory effects. Its genetic associations with type 2 inflammatory diseases like asthma, allergic rhinitis, and atopic dermatitis remain unclear, prompting this study to explore their potential genetic interplay. Methods: Utilizing two-sample Mendelian randomization (TSMR), we examined the genetic associations using 15 genetic instruments from GWAS datasets. Our analysis focused on celiac disease and its relation to asthma, allergic rhinitis, atopic dermatitis, and IgE-mediated food allergies. A power analysis was conducted to determine the study's detection capabilities, and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using various MR methods. Results: Our Mendelian randomization analysis identified statistically significant genetic associations between celiac disease and several type 2 inflammatory diseases, although these were practically insignificant. Specifically, celiac disease was associated with a slight increase in the risk of atopic dermatitis (OR = 1.037) and a minor protective effect against asthma (OR = 0.97). The link with allergic rhinitis was statistically detectable (OR = 1.002) but practically negligible. Despite robust statistical confirmation through various sensitivity analyses, all observed effects remained within the range of practical equivalence (ROPE). Conclusions: Our study identifies potential genetic associations between celiac disease and certain type 2 inflammatory diseases. However, these associations, predominantly within the ROPE range, suggest only limited clinical implications. These findings highlight the need for cautious interpretation and indicate that further exploration for clinical applications may not be warranted at this stage.

Atopic manifestations of inborn errors of immunity

PURPOSE OF REVIEW

Allergy and atopic features are now well recognized manifestations of many inborn errors of immunity (IEI), and indeed may be the hallmark in some, such as DOCK8 deficiency. In this review, we describe the current IEI associated with atopy, using a comprehensive literature search and updates from the IUIS highlighting clinical clues for underlying IEI such as very early onset of atopic disease or treatment resistance to enable early and accurate genetic diagnosis.

RECENT FINDINGS

We focus on recently described genes, their categories of pathogenic mechanisms and the expanding range of potential therapies.

SUMMARY

We highlight in this review that patients with very early onset or treatment resistant atopic disorders should be investigated for an IEI, as targeted and effective therapies exist. Early and accurate genetic diagnosis is crucial in this cohort to reduce the burden of disease and mortality.

Allergy and autoimmunity in children: non-mutually exclusive diseases. A narrative review

In last decades a simultaneous increase in the prevalence of atopic and autoimmune disorders in pediatric population has been observed. Despite the Th1-Th2 paradigm, supporting the polarization of the immune system with Th1 response involved in autoimmune diseases and Th2 response leading to hypersensitivity reactions, recent evidence suggests a possible coexistence of common pathogenic pathways as result of shared immune dysregulation. Similar genes and other mechanisms such as epithelial barrier damage, gut microbiota dysbiosis and reduced number of T regs and IL-10 contribute to the onset of allergy and autoimmunity. IgA deficiency is also hypothesized to be the crosslink between celiac disease and allergy by lowering gut mucous membrane protection from antigens and allergens. The present narrative review aims to give an overview of the co-occurrence of allergic and autoimmune disorders (celiac disease, inflammatory bowel diseases, type 1 diabetes mellitus, thyroid disease, juvenile idiopathic arthritis) in pediatric population, based on the available evidence. We also highlighted the common pathogenic pathways that may underpin both. Our findings confirm that allergic and autoimmune diseases are commonly associated, and clinicians should therefore be aware of the possible coexistence of these conditions in order to ameliorate disease management and patient care. Particular attention should be paid to the association between atopic dermatitis or asthma and celiac disease or type 1 diabetes and vice versa, for therapeutic interventions. Further studies are needed to better clarify mechanisms involved in the pathogenesis and eventually identify new therapeutic strategies.

Clinical manifestation for immunoglobulin A deficiency: a systematic review and meta-analysis

OBJECTIVES

Immunoglobulin A deficiency (IgAD) is a common disease with an unknown genetic defect, characterized by the decreased or absent IgA with other isotypes normal, normal subclasses, and specific antibodies. Patients with this disorder represent a spectrum of clinical manifestations including infections, autoimmune disorders, malignancy, and allergic diseases. The current study aimed to evaluate their prevalence and categorized them.

METHODS

We searched PubMed, Web of Science, and Scopus databases to find eligible studies from the earliest available date to January 2022 with standard keywords. Pooled estimates of clinical manifestations prevalence and the corresponding 95% confidence intervals were calculated using random-effects models.

RESULTS

The most prevalent clinical manifestations belonged to infection (64.8%) followed by allergic diseases (26.16%) and autoimmunity (22.0%), respectively. In selective IgA deficiency patients as the largest group of IgAD in current study, celiac disease (6.57%), Inflammatory bowel disease (4.01%), and rheumatoid arthritis (3.80%) were the most prevalent autoimmunity. Meanwhile, the most frequent infection was respiratory tract infection, fungal infection, and gastrointestinal infection at 50.74%, 18.48%, and 15.79%, respectively. In addition, the pooled prevalence of asthma, allergic rhinitis, and allergic conjunctivitis were 19.06%, 15.46%, and 11.68%, respectively which were reported as the most widespread allergic diseases.

CONCLUSIONS

Our results showed that apart from undiagnosed IgAD patients, IgAD patients represent a wide range of clinical manifestations. Infection, allergy, and autoimmunity are the most common clinical manifestations. The concurrent presence of IgA and IgG subtypes deficiency could be associated with increased susceptibility to infection. Considering the probability of developing new clinical complications during follow-up, periodic assessments of IgAD patients should be inspected.

Antibody-mediated regulation of basophils: emerging views and clinical implications

An increasing number of human diseases, including allergies, infections, inflammation, and cancer, involve roles for basophils. Traditionally viewed as the rarest leukocytes that are present only in the circulation, basophils have recently emerged as important players in systemic as well as tissue-specific immune responses. Their functions are regulated by immunoglobulins (Igs), and this enables basophils to integrate diverse adaptive and innate immunity signals. IgE is well known to regulate basophil responses in the context of type 2 immunity and allergic inflammation; however, growing evidence shows that IgG, IgA, and IgD also shape specific aspects of basophil functions relevant to many human diseases. We discuss recent mechanistic advances underpinning antibody-mediated basophil responses and propose strategies for the treatment of basophil-associated disorders.

Quantitative proteomics profiling of plasma from children with asthma

A lack of validated blood diagnostic markers presents an obstacle to asthma control. The present study sought to profile the plasma proteins of children with asthma and to determine potential biomarkers. Plasma samples from children in acute exacerbation (n = 4), in clinical remission (n = 4), and from healthy children (n = 4, control) were analyzed using a tandem mass tag (TMT)-labeling quantitative proteomics and the candidate biomarkers were validated using liquid chromatography-parallel reaction monitoring (PRM)/mass spectrometry (MS) with enzyme-linked immunosorbent assay (ELISA). We identified 347 proteins with differential expression between groups: 125 (50 upregulated, 75 downregulated) between acute exacerbation and control, 142 (72 upregulated, 70 downregulated) between clinical remission and control, and 55 (22 upregulated, 33 downregulated) between acute and remission groups (all between-group fold changes > 1.2; P < 0.05 by Student's t-test). Gene ontology analysis implicated differentially expressed proteins among children with asthma in immune response, the extracellular region, and protein binding. Further, KEGG pathway analysis of differentially expressed proteins identified complement and coagulation cascades and Staphylococcus aureus infection pathways as having the highest protein aggregation. Our analyses of protein interactions identified important node proteins, particularly KRT10. Among 11 differentially expressed proteins, seven proteins (IgHD, IgHG4, AACT, IgHA1, SAA, HBB, and HBA1) were verified through PRM/MS. Protein levels of AACT, IgA, SAA, and HBB were verified through ELISA and may be useful as biomarkers to identify individuals with asthma. In conclusion, our study presents a novel comprehensive analysis of changes in plasma proteins in children with asthma and identifies a panel for accessory diagnosis of pediatric asthma.

IgE-Dependent Food Sensitisation and Its Role in Clinical and Laboratory Presentation of Paediatric Inflammatory Bowel Disease

The rising prevalence of inflammatory bowel disease (IBD) and food allergies and their partially overlapping mechanisms such as microbiome diversity reduction raise questions about the role of allergies in IBD. While data on their comorbidity are available, analysis of IgE-sensitization's influence on the clinical presentation of IBD is lacking and is the aim of this study. Histories of 292 children with newly diagnosed IBD (173 cases of ulcerative colitis, 119 cases of Crohn's disease) were analyzed. Disease age of onset, activity, location, behaviour, and anthropometric and laboratory parameters were tested for its dependence on the presence of chosen IgE sensitization markers. A.o. Chi2, OR and phi coefficient were assessed. In Crohn's disease (CD), elevated total IgE (tIgE) correlated with weight loss, rectal bleeding, ASCA IgG positivity (φ = 0.19 for all) and negatively correlated with complicated disease behaviour (φ = -0.19). TIgE > 5 × reference range correlated with being underweight (φ = 0.2), ASCA IgG positivity (φ = 0.3), ASCA double (IgA and IgG) positivity (φ = 0.25) and elevated total IgG (φ = 0.18). The presence of specific IgEs (sIgE) correlated with extraintestinal manifestations of IBD (φ = 0.19): Egg white sIgE correlated with upper GI involvement (L4b) (φ = 0.26), severe growth impairment (φ = 0.23) and colonic mucosal eosinophilia (φ = 0.19). In ulcerative colitis, decreased IgA correlated with egg white sIgE (φ = 0.3), as well as the presence of any (φ = 0.25) or multiple sIgEs (φ = 0.2); the latter correlated also with elevated IgG (φ = 0.22), fever (φ = 0.18), abdominal pain (φ = 0.16) and being underweight (φ = 0.15). Cow's milk sIgE correlated positively with growth impairment (φ = 0.15) and elevated IgG (φ = 0.17) and negatively with extensive colitis (φ = -0.15). Pancolitis correlated negatively with sIgE presence (φ = -0.15). In summary, single moderate and numerous weak but interesting relationships were observed.

A new hope? Possibilities of therapeutic IgA antibodies in the treatment of inflammatory lung diseases

Inflammatory lung diseases represent a persistent burden for patients and the global healthcare system. The combination of high morbidity, (partially) high mortality and limited innovations in the last decades, have resulted in a great demand for new therapeutics. Are therapeutic IgA antibodies possibly a new hope in the treatment of inflammatory lung diseases? Current research increasingly unravels the elementary functions of IgA as protector against infections and as modulator of overwhelming inflammation. With a focus on IgA, this review describes the pathological alterations in mucosal immunity and how they contribute to chronic inflammation in the most common inflammatory lung diseases. The current knowledge of IgA functions in the circulation, and particularly in the respiratory mucosa, are summarized. The interplay between neutrophils and IgA seems to be key in control of inflammation. In addition, the hurdles and benefits of therapeutic IgA antibodies, as well as the currently known clinically used IgA preparations are described. The data highlighted here, together with upcoming research strategies aiming at circumventing the current pitfalls in IgA research may pave the way for this promising antibody class in the application of inflammatory lung diseases.

When secretion turns into excretion - the different roles of IgA

IgA deficiency is the commonest immunodeficiency affecting up to 1 in 700 individuals. The effects of IgA deficiency are difficult to see in many individuals, are mild in many fewer and severe in fewer still. While monovalent IgA is found in serum, dimeric IgA is secreted through mucosal surfaces where it helps to maintain epithelial homeostasis. Studies with knockout mice have taught us that there are subtle inflammatory consequences of removing secretory IgA (sIgA), and the best explanation for these changes can be related by the loss of the 'excretory' immune system. The excretion of antigens is a logical process in regulating the immune system, given the long half-life of complement fixing antibodies. But the function of IgA as an immune or inflammation regulator may go beyond antigen removal.

Bronchiectasis and obstructive lung diseases in primary antibody deficiencies and beyond: update on management and pathomechanisms

PURPOSE OF REVIEW

Pulmonary complications are among the most frequent manifestations in patients with primary antibody deficiency (PAD), contributing significantly to morbidity and mortality. Here, we focus on recent findings in obstructive pulmonary disease and bronchiectasis in PAD. Since specific data on patients with PAD is limited and management mostly follows general recommendations, this review also aims to summarize data from the immunocompetent population.

RECENT FINDINGS

Potential risk factors for the development and progression of bronchiectasis include reduced immunoglobulins and lower CD4 cells. In addition, Pseudomonas aeruginosa and an altered microbiome might contribute to local inflammation and disease progression. Findings on the contribution of neutrophils and eosinophils in the affected immunocompetent population require confirmation in PAD. Despite its high global burden, there is an extreme paucity of data on chronic obstructive pulmonary disease in PAD. Lower IgA and IgM are associated with asthma in PAD, but the heterogeneity of prevalence among PAD groups is poorly understood. Recent observations of non-IgE-mediated pathomechanisms in asthma may be of particular interest in PAD patients.

SUMMARY

Management of PAD patients with chronic lung disease requires a multidisciplinary team approach including immunology, pulmonology, infectious disease and physiotherapy. Diagnostic processes should be harmonized to ensure a more precise perspective on prevalence and disease courses.

Risk Factors Affecting Development and Persistence of Preschool Wheezing: Consensus Document of the Emilia-Romagna Asthma (ERA) Study Group

Wheezing at preschool age (i.e., before the age of six) is common, occurring in about 30% of children before the age of three. In terms of health care burden, preschool children with wheeze show double the rate of access to the emergency department and five times the rate of hospital admissions compared with school-age asthmatics. The consensus document aims to analyse the underlying mechanisms involved in the pathogenesis of preschool wheezing and define the risk factors (i.e., allergy, atopy, infection, bronchiolitis, genetics, indoor and outdoor pollution, tobacco smoke exposure, obesity, prematurity) and the protective factors (i.e., probiotics, breastfeeding, vitamin D, influenza vaccination, non-specific immunomodulators) associated with the development of the disease in the young child. A multidisciplinary panel of experts from the Emilia-Romagna Region, Italy, addressed twelve key questions regarding managing preschool wheezing. Clinical questions have been formulated by the expert panel using the PICO format (Patients, Intervention, Comparison, Outcomes). Systematic reviews have been conducted on PubMed to answer these specific questions and formulate recommendations. The GRADE approach has been used for each selected paper to assess the quality of the evidence and the degree of recommendations. Based on a panel of experts and extensive updated literature, this consensus document provides insight into the pathogenesis, risk and protective factors associated with the development and persistence of preschool wheezing. Undoubtedly, more research is needed to improve our understanding of the disease and confirm the associations between certain factors and the risk of wheezing in early life. In addition, preventive strategies must be promoted to avoid children's exposure to risk factors that may permanently affect respiratory health.

Harnessing Nasal Immunity with IgA to Prevent Respiratory Infections

The nasal cavity is a primary checkpoint for the invasion of respiratory pathogens. Numerous pathogens, including SARS-CoV-2, S. pneumoniae, S. aureus, etc., can adhere/colonize nasal lining to trigger an infection. Secretory IgA (sIgA) serves as the first line of immune defense against foreign pathogens. sIgA facilitates clearance of pathogenic microbes by intercepting their access to epithelial receptors and mucus entrapment through immune exclusion. Elevated levels of neutralizing IgA at the mucosal surfaces are associated with a high level of protection following intranasal immunizations. This review summarizes recent advances in intranasal vaccination technology and challenges in maintaining nominal IgA levels at the mucosal surface. Overall, the review emphasizes the significance of IgA-mediated nasal immunity, which holds a tremendous potential to mount protection against respiratory pathogens.

The Allergic Phenotype of Children and Adolescents with Selective IgA Deficiency: A Longitudinal Monocentric Study

Background: Selective IgA deficiency (SIgAD) is the most common inborn error of immunity. The exact prevalence and pathogenesis of allergy in SIgAD have not yet been defined. We aimed to describe the prevalence and the characteristics of allergy in pediatric SIgAD subjects, evaluate the association between allergy and other comorbidities, and define the immune phenotype of allergic and non-allergic patients. Methods: Clinical and immunological data from 67 SIgAD patients were collected over a 13-year period at a single center. Patients’ characteristics were analyzed according to the presence of allergy. Results: Allergy was diagnosed in 34% of SIgAD patients, with a median age at allergy diagnosis of 8 years. Allergy was the second-most-common clinical manifestation, following recurrent respiratory infections. Among the allergic group, 74% had rhinitis, 30% asthma, 30% atopic dermatitis, and 22% food allergy; one out of three had more than one allergic manifestation. SIgAD patients showed more frequent transitory lymphopenia and a lower count of CD19+ at diagnosis than at last FU. However, compared to non-allergic subjects, allergic patients did not differ in their immune phenotype, number and severity of infections, or increased autoimmunity. Conclusions: In our longitudinal study, compared to non-allergic SIgAD patients, those with allergies did not present a more severe immune defect or complex clinical phenotype. However, evaluation and early identification of allergy in the context of SIgAD assessment, both at diagnosis and during FU, and definition of a proper management are important to prevent complications and improve the patient’s quality of life.