Types Of Primary Immunodeficiencies Research Articles

Inborn error of immunity associated with allergic and allergic like symptoms

Introduction: Inborn error of immunity (IEI) includes variety of genetic disorders that affect both the innate and acquired immune system. The number of primary immune deficiency disorders is increasing due to advanced laboratory testing methods. The patients with IEI are susceptible to multiple infectious and non-infectious diseases، including autoimmune disorders، allergies، and malignancies. Several studies have shown an increasing prevalence of non-infectious disorders in patients in IEI. Among the non-infectious manifestations of primary immunodeficiency، allergic symptoms can play an effective and important role in diagnosis and treatment of these patients.
 Methods: Articles were searched in Google Scholar، PubMed، Web of Science، and Scopus databases. In this review، we have tried to use the latest and most reliable articles related to the subject that have been published in Persian and English language.
 Conclusion: Allergic diseases can be a common part of some primary immunodeficiency diseases. Even in some types of primary immunodeficiency، they are considered the main symptom and important indicator of the disease، which are very decisive factors for the diagnosis of immunodeficiency.

Gene Signature of Regulatory T Cells Isolated from Children with Selective IgA Deficiency and Common Variable Immunodeficiency.

Selective IgA deficiency (SIgAD) is the most common form and common variable immunodeficiency (CVID) is the most symptomatic form of predominant antibody deficiency. Despite differences in the clinical picture, a similar genetic background is suggested. A common feature of both disorders is the occurrence of autoimmune conditions. Regulatory T cells (Tregs) are the major immune cell type that maintains autoimmune tolerance. As the different types of abnormalities of Treg cells have been associated with autoimmune disorders in primary immunodeficiency (PID) patients, in our study we aimed to analyze the gene expression profiles of Treg cells in CVID and SIgAD patients compared to age-matched healthy controls. The transcriptome-wide gene profiling was performed by microarray technology. As a result, we analyzed and visualized gene expression patterns of isolated population of Treg cells. We showed the differences at the gene level between patients with and without autoimmunizations. Our findings suggest that the gene signatures of Treg cells isolated from SIgAD and CVID patients differ from age-matched healthy controls and from each other, presenting transcriptional profiles enriched in innate immune or Th response, respectively. The occurrence of autoimmunity in both types of PID is associated with down-regulation of class I IFNs signaling pathways. In summary, our findings improve our understanding of Treg dysfunctions in patients with common PIDs and associated autoimmunity.

ЗНАЧЕНИЕ ИММУНОЛОГИЧЕСКОГО СКРИНИНГА В ПРОГНОЗИРОВАНИИ ИНФЕКЦИОННЫХ ОСЛОЖНЕНИЙ КАРДИОХИРУРГИИ

Incidence of infectious complications in children with congenital heart disease, especially with cyanotic and complex defects, is higher than in the population, which is associated with both hemodynamic and immune disorders. Various types of primary immunodeficiencies in congenital heart disease and the dependence of immune disorders on the morphology of the defect, the severity of circulatory failure and arterial hypoxemia are described. The importance of diagnosing immunological disorders is emphasized to reduce the risk of infectious complications of cardiac surgery, reduce mortality and improve the outcomes of surgical interventions for congenital heart disease. The prognostic value of immune disorders identified by the TREC/KREC method for infectious complications of cardiac surgery has not been studied. The purpose of this research was to assess the possibility of predicting infectious complications of cardiac surgery in children with congenital heart disease based on screening using the TREC/KREC method. Material and methods used: preoperatively, 200 children with congenital heart disease aged 3 days to 12 months old were examined. Instrumental and laboratory methods were used including immunological screening for TREC/KREC DNA. Results: 123 (62.4%) were diagnosed with “acyanotic” congenital heart disease, 74 (37.5%) with various cyanotic congenital heart diseases and 10 (5%) with congenital heart diseases with Down syndrome, Di George syndrome, Williams syndrome or multiple malformations. 184 (92%) underwent various cardiac surgical interventions. Violations of T-cell immunity according to preoperative TREC/KREC screening were observed in 23.5% of cases including in all children with syndromic forms of congenital heart disease, multiple malformations, and significantly more often in cyanotic congenital heart disease, conotruncal defects, and those admitted in critical conditions. Infectious complications of cardiac surgery were observed significantly more often in this group than in children with normal T-cell immunity (in 36% and 3.6%, respectively). Conclusion: the prognostic value of TREC/KREC screening for targeted preparation and postoperative management in order to prevent infectious complications of cardiac surgery has been confirmed.

A Review of Primary Immuno-deficiency Disorders Predisposing to Cancer

Introduction: Primary immunodeficiencies are relatively rare and heterogeneous disorders in which one or more component of immune system have genetic defect. The majority of the patients suffer from frequent infections with different microorganisms according to the type of disorder they have. Some people with primary immunodeficiency are susceptible to malignant diseases. The type of malignancy depends on the type of primary immunodeficiency, age of the patient and the type of virus infection. Many advances have been made in understanding of molecular mechanisms in humeral and cellular immune defects. Furthermore، our knowledge has been increased about the incidence of infections and tumors in primary immunodeficiency and this helps us in early diagnosis of disorders and their complications. Several evidences support the theory that the immune system plays a major role in the occurrence of many malignant diseases. Articles have been searched on Google Scholar، PubMed، Web of Science، and Scopus databases. In this review، the latest and most reliable articles related to the subject that had been published in English language were used.
 Conclusion: Since the patients with primary immunodeficiency are prone to multiple infections, various malignancies can be seen in these people. The recurrence of some malignancies in families, especially blood malignancies may be due to primary immunodeficiency and we should consider evaluation of immune system.

Immunodeficiency Disorders in Congenital Heart Diseases (Review)

The study data of the last two decades on primary and secondary immunodeficiency in congenital heart defects (CHD) as a cause of frequent infectious complications before and after cardiac surgery are presented. Based on screenings of various levels, data are provided on the greater severity of immunological disorders in critical and cyanotic CHD in conotruncal defects compared with those in septal defects and stenotic defects. Violations were more often related to T-cell function and immunoglobulin deficiency (especially the IgG and IgG4 subgroups). Various types of primary immunodeficiency were found in 13 genetic syndromes in combination with CHD. The review discusses the possibility of using the technique of quantitative determination of DNA TREC and KREC — by-products of maturation of T- and B-cell receptors, which allows us to judge the defects of the T- and B-cell links of the immune system to predict infectious complications in children with CHD. The data of our own study of 200 infants with CHD (in 5% of cases with syndromic forms of CHD) are presented, where a decrease in TREC was found in 23.5% of cases, including all infants with syndromic forms, more often with cyanotic and conotruncal CHD and in children admitted in critical conditions. In children with reduced TREC values, infectious complications in the postoperative period were observed significantly more often than in children with normal indicators (36 and 3.6%, respectively). The analysis of publications confirmed the importance of TREC and KREC screening for targeted preoperative preparation in order to reduce postoperative complications and reduce the risk of mortality in CHD.

The use of next generation sequencing technologies for the diagnosis of inborn errors of immunity

Primary immunodeficiencies are congenital genetically determined immune disorders. Recent advances in molecular genetic technologies have enabled a simultaneous analysis of a large number of genes in a patient. The purpose of this study was to analyze the mutational spectrum in DNA samples collected from patients with various types of primary immunodeficiencies. In this study, we applied next-generation sequencing technology using a panel developed at the Belarusian Research Center for Pediatric Oncology, Hematology and Immunology and consisting of 290 genes that are associated with primary immunodeficiencies according to the existing literature. The testing was carried out in 96 patients with a clinical history suggesting a primary immunological defect. As a result, 37.5% of cases (36/96 patients) were found to harbor genetic defects that lead to disorders of the immune system.

Mycoplasma pneumoniae Infections and Primary Immune Deficiencies.

Mycoplasma pneumoniae (M. pneumoniae) is one of the leading causes of community-acquired pneumonia in children and is also implicated in a variety of reactive extrapulmonary diseases. Recurrent and/or severe respiratory infections are one of the most frequent manifestations of several types of primary immunodeficiency. Here, we reviewed the medical literature to assess the potential relevance of M. pneumoniae in the infections observed in children affected with combined, humoral, and innate primary immune deficiencies. M. pneumoniae does not result to be epidemiologically prevalent as a cause of pneumonia in children affected by primary immunodeficiencies, but this infection can have a persistent or severe course in this category of patients. Indeed, the active search of M. pneumoniae could be useful and appropriate especially in children with humoral immune deficiencies. Indeed, most cases of M. pneumoniae infection in primary immunodeficiencies are described in patients affected by a/hypo-gammaglobulinemia.

Respiratory syncytial virus infections requiring hospitalization in patients with primary immunodeficiency

IntroductionThe aim of the study was to assess the incidence of hospital admission due to severe acute respiratory infection by respiratory syncytial virus (RSV-ARI) in children with primary immunodeficiencies (PIDs) and the severity of RSV-ARI in these patients. MethodsWe conducted a nationwide cross-sectional retrospective and prospective multicentre study in the 2011–2017 period. The study was performed in 15 Spanish hospitals and included children with PID who required hospital admission due to RSV-ARI. ResultsOut of 439 patients with PID followed up at participating hospitals, 13 (3%) required hospital admission due to RSV-ARI. The median age of admitted patients was 1.6 years (interquartile range, 0.5−2.2), and 7 were male. The types of PID most frequently associated with admission due to RSV-ARI were combined immunodeficiency (CID; 4/71; 6%) and CID with associated or syndromic features (CIDwASF; 6/147; 4%). Two of the 13 patients were receiving palivizumab for RSV prophylaxis, and 3 received potentially active therapies against RSV during the hospital stay. Viral coinfection was detected in 6 patients, 5 (39%) developed complications, and 4 (31%) required admission to the paediatric intensive care unit. There were no documented RSV-related deaths. ConclusionsIn the group of patients with PID, severe RSV infection requiring hospitalization is more frequent in patients with CID and CIDwASF, in whom special efforts should be made to prevent RSV infection. Further studies are needed to confirm these results.

Understanding attitudes and obstacles to vaccination against COVID-19 in patients with primary immunodeficiency

BackgroundPatients with primary immunodeficiency (PID) are at increased risk for infections such as SARS-CoV-2 (COVID-19), due to the nature of their diseases and being immunocompromised. At this time, four vaccines against COVID-19 (Pfizer-BioNtech’s Comirnaty®, Moderna’s Spikevax®, AstraZeneca’s Vaxzevria®, Johnson & Johnson’s Janssen®) have been approved for use by Health Canada. Due to the novelty of these vaccines, clinical studies in patients with PID are ongoing. Despite limited evidence, Canada’s National Advisory Committee on Immunization (NACI) recommend that patients with PID without any contraindications should be vaccinated with any of the approved vaccines as the potential benefits of being immunized against the virus likely outweigh the risks of contracting a severe infection. The aim of this study was to understand the perceptions regarding COVID-19 vaccination among patients with PID and to identify specific factors related to vaccine hesitancy.MethodsThe Canadian Immunodeficiencies Patient Organization (CIPO) conducted an online survey of its members to evaluate uptake of the COVID-19 vaccines by patients with PID. Data was collected using a self-administered online questionnaire. The survey was conducted between March and April 2021.ResultsAt the time of survey, among 370 respondents who had not received the COVID-19 vaccine, 302 respondents (81.6%) indicated they were very or somewhat likely to get vaccinated against COVID-19; and 68 respondents (18.4%) indicated they were somewhat or very unlikely, undecided, or not planning to get vaccinated. A large majority of respondents indicated they had a diagnosis of PID (67.8%) and/or specified their type of PID (27.7%). The most common reason for vaccine hesitancy was primarily due to uncertainty about immune response given an underlying immunodeficiency. Other concerns included unknown long-term side effects of COVID-19 vaccination, pre-existing history of allergic reactions, limited amount of data, lack of investigation of safety and effectiveness of COVID-19 vaccines in those with medical conditions, and skepticism of the underlying science and/or the medical system.ConclusionsThe results point to the importance of ongoing patient outreach, education, and up-to-date information on the rapidly evolving scientific knowledge and evidence on COVID-19 relevant to the PID community, from clinical trials to real-world evidence and observational studies.

The Effect of COVID-19 Pandemic on Patients with Primary Immunodeficiency: A Cohort Study.

Both adaptive and innate immune responses are essential for an effective defense against the severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) infection. We aimed to investigate the effect of the coronavirus disease 2019 (COVID-19) pandemic on patients with primary immunodeficiency (PID). This study was performed on patients who were diagnosed with PID by immunologist specialists and referred to Imam Reza Clinic of Asthma and Allergy, affiliated with Shiraz University of Medical Sciences, (Shiraz, Iran) for regular check-ups. The patients were enrolled in this cohort study and followed for any sign of COVID-19 from March 2020 to May 2021. COVID-19 infection was confirmed using a real-time polymerase chain reaction (RT-PCR) assay of nasal and pharyngeal swabs. Among the 90 PID patients under study, nine patients (10%) were diagnosed positive for COVID-19 infection. Five out of these nine patients belonged to the combined immunodeficiency (CID) category, while four patients were categorized as having primary antibody deficiencies (PADs). Eight patients with COVID-19 were required to be admitted to the hospital, and three patients died after hospitalization due to COVID-19 infection. It seems that patients with CID are at a higher risk of mortality, due to COVID-19 infection, that other types of PID.

A Review of Primary Immunodeficiency Diseases with Skin Manifestations

Introduction: Primary immunodeficiencies (PID) are rare heterogeneous disorders with defects in which one or more components of the immune system are malfunctioning. Clinical presentations of the patients according to type of immunodeficiency are variable. The majority of these patients are susceptible to infections depending on the type of disorder. In these patients, one of the most important and common symptoms is a skin manifestation that in many cases helps to diagnose the disease. Skin symptoms can include infectious-inflammatory-autoimmune-allergic manifestations and malignancies. In some cases, skin involvement can be the initial manifestation of immunodeficiency diseases, so understanding the relationship between the type of primary immunodeficiency and the type of skin involvement is very important in diagnosing the disease. The majorities of skin diseases are not pathogenomonic in primary immunodeficiencies and may be seen in other diseases with normal levels of immunity. However, there are numerous skin findings that are so characteristic of immunodeficiency diseases that it is necessary to evaluate the immune system.
 Conclusion: Skin is an organ that may be involved in many diseases, including primary immunodeficiency. Sometimes skin is the first organ involved in immune deficiencies. Therefore, recognizing skin manifestations in these patients is one of the most important factors in early diagnosis of these people.

Creating Awareness for Primary Immunodeficiencies in Japan.

Primary immunodeficiency (PID) is primarily characterized by susceptibility to infectious diseases. In addition, patients with some type of PID are prone to develop autoimmune, autoinflammatory, or malignant diseases. Therefore, the term, inborn errors of immunity (IEI), has been more used rather than PID. In recent years, the number of diseases which belong to PID has been increasing. There were approximately 110 diseases in the report of International Union of Immunological Societies in 1999. Since then, the number increased to 430 diseases in the latest IUIS report in 2019. We conducted PID nationwide survey in Japan for 3 times in the last 15 years. These studies were focused on incidence and complications of PID, the clinical course of viral infection, and methods to prevent infectious diseases in PID patients. For the awareness of PID, it is essential to know the general and fundamental information of PID patients. Needless to say, we need it to offer appropriate medical services for PID patients. Moreover, chances to provide answers to the questionnaires and seeing the results of the analysis should contribute to the awareness of PID among doctors. In this review, I am going to summarize the results of 3 nationwide survey in Japan, and pick up interleukin-1 receptor-associated kinase 4 (IRAK4) deficiency as an example for creating awareness for its appropriate management.

Infecciones por virus respiratorio sincitial que requieren hospitalización en pacientes con inmunodeficiencias primarias

IntroductionThe aim of the study was to assess the incidence of hospital admission due to severe acute respiratory infection by respiratory syncytial virus (RSV-ARI) in children with primary immunodeficiencies (PIDs) and the severity of RSV-ARI in these patients. MethodsWe conducted a nationwide cross-sectional retrospective and prospective multicentre study in the 2011-2017 period. The study was performed in 15 Spanish hospitals and included children with PID who required hospital admission due to RSV-ARI. ResultsOut of 439 patients with PID followed up at participating hospitals, 13 (3%) required hospital admission due to RSV-ARI. The median age of admitted patients was 1.6years (interquartile range, 0.5-2.2), and 7 were male. The types of PID most frequently associated with admission due to RSV-ARI were combined immunodeficiency (CID; 4/71 [6%]) and CID with associated or syndromic features (CIDwASF; 6/147 [4%]). Two of the 13 patients were receiving palivizumab for RSV prophylaxis, and 3 received potentially active therapies against RSV during the hospital stay. Viral coinfection was detected in 6 patients, 5 (39%) developed complications, and 4 (31%) required admission to the paediatric intensive care unit. There were no documented RSV-related deaths. ConclusionsIn the group of patients with PID, severe RSV infection requiring hospitalization is more frequent in patients with CID and CIDwASF, in whom special efforts should be made to prevent RSV infection. Further studies are needed to confirm these results.

Retrospective Analysis of Autoimmune Diseases and Immunologic Characteristics of the Adult Primary Immune Deficiency Cohort: 17 Years Experience of the Tertiary Referral Immunology Center in Turkey

ABSTRACT Objective: Primary immunodeficiencies (PIDs) consist of genetically heterogeneous disorders. The spectrum can include infectious diseases, malignancy, allergy, and autoimmunity. We aimed to analyze the frequency and variety of autoimmune diseases (ADs) in PIDs and describe their clinical and laboratory features. Materials and Methods: Ninety-two patients with PID followed by Ege University Medical Faculty between 2000 and 2017 were enrolled in this retrospective, cross-sectional study. All patients’ medical records were reviewed using the demographic information, type of PIDs and ADs, ADs-related autoantibodies, and basic and immunologic laboratory findings. ADs were diagnosed using clinical and complementary paraclinical findings by an immunologist and/or a subspecialist related to the affected organ or system. Results: We evaluated 50 male and 42 female PID patients with a mean age of 40.92 (18-86). Twenty-nine (32 %) patients (15 females/14 males) with a mean age of 43.8 (19-78) had ADs. In our study group, the most commonly detected type of PID with AD is common variable immune deficiency (CVID) (n=17); followed by combined immune deficiency (CID) (n=3), CTLA4 deficiency (n=2), selective IgA deficiency (sIgAD) (n=2), specific IgG subgroup deficiency (n=1), autoimmune polyglandular syndrome (APS) with hypogammaglobulinemia (n=1), dyskeratosis congenita (DC) (n=1), Osler-Rendu-Weber (ORW) syndrome with CVID-like PID (n=1), and cartilage-hair hypoplasia (CHH) (n=1). According to systematic assessments, ADs resulted in endocrinologic 14%, dermatologic 10.8%, rheumatologic 9.7%, gastroenterological 9.7%, hematological 8.6%, and neurologic disorders 1%. The frequency of ADs was higher in CVID cases than other types of PIDs (p <0.05). Basic and immunologic laboratory findings of the PIDs with and without ADs were analyzed and compared; however, no statical significant difference was obtained between the groups. Conclusion: We have analyzed the frequency and variety of ADs in a adult PID cohort in Turkey. Patients presenting with multiple ADs should be screened for having an underlying PID. Keywords: Primary immune deficiency, autoimmunity, autoantibody, immunologic parameters, frequency

Azithromycin and Co-Trimoxazole in Antimicrobial Prophylaxis: Special Emphasis on Primary Immunodeficiencies in Children

Patients with primary immunodeficiency diseases (PID) are prone to infectious, and they often determine the course of the disease. Antimicrobial prophylaxis for patients with PID includes co-trimoxazole, amoxicillin and macrolides. Co-trimoxazole is a widely used antimicrobial agent for pneumocystosis prophylaxis in immunocompromised patients, including patients with primary cellular immunodeficiency. Antiinflammatory effect of azithromycin made it a drug of choice in the management of chronic lung diseases in the patients with primary immunodeficiencies, especially in those with antibody deficiencies. Further randomised controlled studies are needed to define the optimal agent for all types of primary immunodeficiencies, its dose, duration of treatment, benefits and safety of long-term use.A recommendation for the prophylactic use of long-term therapy should consider the balance between benefits and risk of adverse events.
 Bangladesh Journal of Medical Science Vol.20(3) 2021 p.530-538

Specific Antibody Deficiency in Adult Patients With IgG or IgG Subclass Deficiency

PurposeSpecific antibody deficiency (SAD) involves a deficient response to a polysaccharide vaccine despite having normal immunoglobulin levels. The failure of the polysaccharide response can be observed as a component of various primary antibody deficiencies. However, only a few studies have described the clinical and immunological profiles in SAD and/or other primary immunodeficiencies (PIDs) in adults.MethodsA total of 47 patients who had a clinical history suggestive of antibody deficiency or had already been diagnosed with various antibody deficiencies were enrolled. Polysaccharide responses to 7 pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F and 23F) were measured using the World Health Organization enzyme-linked immunosorbent assay (WHO-ELISA), and postvaccination immunoglobulin G (IgG) titers were compared to clinical and laboratory parameters.ResultsBased on the American Academy of Allergy, Asthma, and Immunology (AAAAI) criteria for the WHO-ELISA, 11 (23.4%) patients were diagnosed as having SAD. Sixteen-three percent of them had combined with other types of PID, such as IgG subclass deficiency and hypogammaglobulinemia. Postvaccination IgG titers for the serotypes 4/9V/18C correlated with IgG2 (P = 0.012, P = 0.001, and P = 0.004) and for 6B/9V/14 with IgG3 (P = 0.003, P = 0.041, and P = 0.036, respectively). The IgG3 subclass levels negatively correlated with forced expiratory volume in 1 second (FEV1, %) and FEV1/forced vital capacity (P < 0.001 and P = 0.001, respectively).ConclusionSAD can be diagnosed in patients with normal IgG levels as well as in those deficient in IgG or the IgG3 subclass, implicating that restricted responses to Streptococcus pneumoniae polysaccharide antigens commonly exist in patients with predominantly antibody deficiency.

Impact of SARS-CoV-2 Pandemic on Patients with Primary Immunodeficiency

Although it is estimated that COVID-19 life-threatening conditions may be diagnosed in less than 1:1000 infected individuals below the age of 50, but the real impact of this pandemic on pediatric patients with different types of primary immunodeficiency (PID) is not elucidated. The current prospective study on a national registry of PID patients showed that with only 1.23 folds higher incidence of infections, these patients present a 10-folds higher mortality rate compared to population mainly in patients with combined immunodeficiency and immune dysregulation. Therefore, further management modalities against COVID-19 should be considered to improve the survival rate in these two PID entities using hematopoietic stem cell transplantation and immunomodulatory agents.

Prophylaxis of Upper Airway Infections in a Patient with Partial IgA Deficiency: Concurrent Use of Sublingual Immunotherapy with Inactivated Whole-Cell Bacterial Extract and Der p1

Selective IgA deficiency is the most common type of primary immunodeficiency, but there is not yet a specific effective treatment. The most prevalent clinical manifestations are infectious diseases of the respiratory system. We report herein the case of an 11-year-old female with selective IgA deficiency and recurring episodes of respiratory infections associated with rhinitis and asthma. We evaluated the efficacy of sublingual immunotherapy combined with inactivated whole-cell bacterial extract and Der p1-specific immunotherapy. After 18 months of clinical follow-up, we observed a significant reduction in the number of episodes of respiratory infections associated with control of atopic diseases. We also observed a 3-fold increase in serum IgA levels compared to treatment initiation. This case demonstrates the potential utility of the concurrent use of sublingual immunotherapy with inactivated whole-cell bacterial extract and Der p1 for successful control of allergy and infection in partial selective IgA deficiency.

Il deficit di IgA

IgA deficiency (D-IgA) in the paediatric population is often an occasional finding during tests performed for other reasons in children in whom an immunodeficiency disorder is not suspected. D-IgA is the most common primary immunodeficiency with a variable prevalence according to ethnicity, estimated on 1 case/600 in the Caucasian population. IgA should be dosed twice in a child &gt; 4 years of age to confirm the deficiency, which is defined by the presence of serum IgA &lt; 0.07 g/l. The other classes of immunoglobulins should always be dosed. Most patients with D-IgA will not require any treatment or follow-up (85% are asymptomatic), apart from screening for coeliac disease, which is 10 to 20 times more frequent in patients with D-IgA. In the case of a child with D-IgA with recurrent infections (mainly affecting the respiratory and, less commonly, the gastrointestinal tract), signs and symptoms of alarm must always be sought and valued for other types of primary immunodeficiency (especially the common variable immunodeficiency), which, although rarely, can be associated with D-IgA. Patients with D-IgA, in particular adolescents and adults, have a higher risk than the general population of developing autoimmune diseases. The family should be informed of this possible occurrence, but specific laboratory evaluations are not necessary. Four clinical cases are presented: an occasional finding of D-IgA in a healthy child, the association with coeliac disease, the association with juvenile idiopathic arthritis, and IgA deficiency in a patient with an immunodeficiency disorder (ataxia-telangectasia).

Coordinated regulation of scaffold opening and enzymatic activity during CARD11 signaling

The activation of key signaling pathways downstream of antigen receptor engagement is critically required for normal lymphocyte activation during the adaptive immune response. CARD11 is a multidomain signaling scaffold protein required for antigen receptor signaling to NF-κB, c-Jun N-terminal kinase, and mTOR. Germline mutations in the CARD11 gene result in at least four types of primary immunodeficiency, and somatic CARD11 gain-of-function mutations drive constitutive NF-κB activity in diffuse large B cell lymphoma and other lymphoid cancers. In response to antigen receptor triggering, CARD11 transitions from a closed, inactive state to an open, active scaffold that recruits multiple signaling partners into a complex to relay downstream signaling. However, how this signal-induced CARD11 conversion occurs remains poorly understood. Here we investigate the role of Inducible Element 1 (IE1), a short regulatory element in the CARD11 Inhibitory Domain, in the CARD11 signaling cycle. We find that IE1 controls the signal-dependent Opening Step that makes CARD11 accessible to the binding of cofactors, including Bcl10, MALT1, and the HOIP catalytic subunit of the linear ubiquitin chain assembly complex. Surprisingly, we find that IE1 is also required at an independent step for the maximal activation of HOIP and MALT1 enzymatic activity after cofactor recruitment to CARD11. This role of IE1 reveals that there is an Enzymatic Activation Step in the CARD11 signaling cycle that is distinct from the Cofactor Association Step. Our results indicate that CARD11 has evolved to actively coordinate scaffold opening and the induction of enzymatic activity among recruited cofactors during antigen receptor signaling.