Transmembrane activator and calcium-modulating cyclophilin ligand interactor mutations in common variable immunodeficiency: clinical and immunologic outcomes in heterozygotes

Clinical exome sequencing data from patients with inborn errors of immunity: Cohort level diagnostic yield and the benefit of systematic reanalysis

While next generation sequencing has expanded the scientific understanding of Inborn Errors of Immunity (IEI), the clinical use and re-use of exome sequencing is still emerging. We revisited clinical exome data from 1300 IEI patients using an updated in silico IEI gene panel. Variants were classified and curated through expert review. The molecular diagnostic yield after standard exome analysis was 11.8 %. Through systematic reanalysis, we identified variants of interest in 5.2 % of undiagnosed patients, with 76.7 % being (candidate) disease-causing, providing a (candidate) diagnosis in 15.2 % of our cohort. We find a 1.7 percentage point increase in conclusive molecular diagnoses. We find a high degree of actionability in patients with a genetic diagnosis (76.4 %). Despite the modest absolute diagnostic gain, these data support the benefit of iterative exome reanalysis in IEI patients, conveying the notion that our current understanding of genes and variants involved in IEI is by far not saturated.

Genetics and clinical phenotypes in common variable immunodeficiency

Common variable immunodeficiency (CVID) is one of the most common symptomatic groups of inborn errors of immunity. In addition to infections resulting from insufficient levels of immune globulins and antibodies, many patients develop inflammatory or autoimmune conditions, which are associated with increased mortality. This aspect of CVID has been the focus of many studies, and dissecting the clinical phenotypes of CVID, has had the goal of providing biomarkers to identify these subjects, potentially at the time of diagnosis. With the application of whole exome (WES) and whole genome analyses, an increasing number of monogenic causes of CVID have been elucidated. From the standpoint of the practicing physician, an important question is whether the clinical phenotype, particularly the occurrence of autoinflammation of autoimmunity, might suggest the likelihood of identifying a causative mutation, and if possible the gene most likely to underlie CVID. We addressed this question in a patient group of 405 subjects diagnosed with CVID from one medical center.

Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is the most common primary immune deficiency characterized by impaired production of specific immunoglobulin. The clinical manifestations are heterogeneous including acquisition of recurrent bacterial infections after a period of wellness, lymphoproliferation, autoimmunity, pulmonary disease, liver disease, enteropathy, granulomas, and an increased risk of malignancy. The etiology of CVID is largely unknown, with a considerable number of patients having an underlying genetic defect causing immune dysregulation. The antibody deficiency found in CVID is treated with lifelong immunoglobulin therapy, which is preventative of the majority of infections when given regularly.

Refractory Status Epilepticus Associated With a Pathogenic Variant in TNFRSF13B

Febrile infection-related epilepsy syndrome (FIRES) is a rare epileptic syndrome characterized by new-onset refractory status epilepticus preceded by a febrile illness. Limited literature exists regarding the relationship between primary immunodeficiencies and immune-mediated epilepsy, and the relationship between new-onset refractory status epilepticus and common variable immunodeficiency (CVID) is not well-understood. We present a case of a 21-year-old female with a history of recurrent sinus infections, asthma, thrombocytopenia, atrioventricular nodal reentrant tachycardia, and neonatal seizures who presented with fever and new-onset status epilepticus. She was ultimately diagnosed with a heterozygous variant in TNFRSF13B c.311G>A (p.Cys104Tyr), which encodes for a tumor necrosis factor receptor implicated in CVID.

TNFRSF13B/TACI Mutations in Patients with Chronic Rhinosinusitis with Nasal Polyps

BACKGROUND

The pathogenesis of Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) remains still inconclusive. Recent studies identified an increased expression of BAFF (a B cell-activating factor) and its receptor TACI (Transmembrane Activator and cAML Interactor) in nasal polyp samples, while TNFRSF13B/TACI mutations have been found in patients with benign lymphoproliferative disorders and primary antibody deficiencies.

OBJECTIVE

The aim of our study was to evaluate the possible contribution of TNFRSF13B/TACI mutations in CRSwNP pathogenesis.

METHODS

Forty-four (44) patients with CRSwNP (male/female: 33/11, mean age: 52.5 years, range: 16-83) were analyzed for TNFRSF13B/TACI mutations by PCR-sequencing.

RESULTS

No pathogenic TNFRSF13B/TACI mutations were identified in our cohort study of CRSwNP patients. We detected two common missense mutations (p.P251L and p.V220A), along with other common silent mutations and intronic polymorphisms in an identical prevalence to healthy control population.

CONCLUSION

TNFRSF13B/TACI mutations might not play a role in the pathogenesis of CRSwNP.

Autoimmune disorders associated with common variable immunodeficiency: prediction, diagnosis, and treatment

INTRODUCTION

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency. Due to the wide spectrum of the CVID manifestations, the differential diagnosis becomes complicated, ends in a diagnostic delay and increased morbidity and mortality rates. Autoimmunity is one of the important complications associated with CVID. While immunoglobulin replacement therapy has considerably decreased the mortality rate in CVID patients, mainly infection-related mortality, other complications such as autoimmunity appeared prevalent and, in some cases, life threatening.

AREAS COVERED

In this article, genetics, responsible immune defects, autoimmune manifestations in different organs, and the diagnosis and treatment processes in CVID patients are reviewed, after searching the literature about these topics.

EXPERT OPINION

Considering the many phenotypes of CVID and the fact that it remained undiagnosed until older ages, it is important to include various manifestations of CVID in the differential diagnosis. Due to the different manifestations of CVID, including autoimmune diseases, interdisciplinary collaboration of physicians from different fields is highly recommended, as discussed in the manuscript. Meanwhile, it is important to determine which patients could benefit from genetic diagnostic studies since such studies are not necessary for establishing the diagnosis of CVID.

Autoimmunity in Primary Immunodeficiencies (PID)

Primary immunodeficiency (PID) may impact any component of the immune system. The number of PID and immune dysregulation disorders is growing steadily with advancing genetic detection methods. These expansive recognition methods have changed the way we characterize PID. While PID were once characterized by their susceptibility to infection, the increase in genetic analysis has elucidated the intertwined relationship between PID and non-infectious manifestations including autoimmunity. The defects permitting opportunistic infections to take hold may also lead the way to the development of autoimmune disease. In some cases, it is the non-infectious complications that may be the presenting sign of PID autoimmune diseases, such as autoimmune cytopenia, enteropathy, endocrinopathies, and arthritis among others, have been reported in PID. While autoimmunity may occur with any PID, this review will look at certain immunodeficiencies most often associated with autoimmunity, as well as their diagnosis and management strategies.

Establishing the Molecular Diagnoses in a Cohort of 291 Patients With Predominantly Antibody Deficiency by Targeted Next-Generation Sequencing: Experience From a Monocentric Study

Predominantly antibody deficiencies (PAD) are a heterogeneous group of disorders characterized by dysfunctional antibody production, low immunoglobulin levels in serum and impaired vaccine responses. The clinical picture is variable, ranging from mild symptoms to severe complications, which may include autoimmunity, gastrointestinal disease, allergy, and malignancies. If left untreated, PAD patients are at risk of enduring disease progression, irreversible organ damage, and reduced life expectancy. A timely diagnosis has been shown to significantly improve disease prognosis. Here, we report on our experience using targeted gene panel sequencing by employing Agilent's HaloPlex or SureSelect and Illumina's MiSeq technologies in a cohort of 291 individuals who presented with low or absent immunoglobulin levels in combination with or without other clinical features. In total, we have detected over 57 novel or previously reported relevant mutations in ADA, ADA2, BTK, CTLA4, LRBA, NFKB1, NFKB2, PIK3CD, STAT3, and TNFRSF13B. Overall, a genetic diagnosis could be made in 24.7% of the investigated patients. The percentage of coverage for the targeted regions ranged from 90% to 98% in this study. Moreover, functional assays were performed on a defined group of the patients carrying candidate variants in CTLA4, LRBA, NFKB1 and BTK, which confirmed their deleterious effect on protein expression and/or function. This study reiterates that the immunological heterogeneity of predominantly antibody deficiencies may have a diverse genetic origin, although certain clinical features may hint towards a specific group of defects. Employing targeted sequencing panels proves to be a very time- and cost-efficient, yet reliable, method for the establishment of a genetic diagnosis in individuals with PAD. However, in case of negative panel results, or if functional testing reveals inconspicuous observations in patients with a clear indication for genetic testing, further work-up including whole exome or whole genome sequencing should be considered.

Bowel Histology of CVID Patients Reveals Distinct Patterns of Mucosal Inflammation

Diarrhea is the commonest gastrointestinal symptom in patients with common variable immunodeficiency (CVID). Different pathologies in patients' bowel biopsies have been described and links with infections have been demonstrated. The aim of this study was to analyze the bowel histology of CVID patients in the Royal-Free-Hospital (RFH) London CVID cohort. Ninety-five bowel histology samples from 44 adult CVID patients were reviewed and grouped by histological patterns. Reasons for endoscopy and possible causative infections were recorded. Lymphocyte phenotyping results were compared between patients with different histological features. There was no distinctive feature that occurred in most diarrhea patients. Out of 44 patients (95 biopsies), 38 lacked plasma cells. In 14 of 21 patients with nodular lymphoid hyperplasia (NLH), this was the only visible pathology. In two patients, an infection with Giardia lamblia was associated with NLH. An IBD-like picture was seen in two patients. A coeliac-like picture was found in six patients, four of these had norovirus. NLH as well as inflammation often occurred as single features. There was no difference in blood lymphocyte phenotyping results comparing groups of histological features. We suggest that bowel histology in CVID patients with abdominal symptoms falls into three major histological patterns: (i) a coeliac-like histology, (ii) IBD-like changes, and (iii) NLH. Most patients, but remarkably not all, lacked plasma cells. CVID patients with diarrhea may have an altered bowel histology due to poorly understood and likely diverse immune-mediated mechanisms, occasionally driven by infections.

TACI Mutations in Primary Antibody Deficiencies: A Nationwide Study in Greece

Background and objectives: Monoallelic (heterozygous) or biallelic (homozygous or compound heterozygous) TACI mutations have been reported as the most common genetic defects in patients with common variable immunodeficiency (CVID), which is the most common clinically significant primary immunodeficiency in humans. The aim of our study was to evaluate the prevalence and any correlations of TACI defects in Greek patients with primary antibody deficiencies. Materials and Methods: 117 patients (male/female: 53/64) with CVID (110) and a combined IgA and IgG subclass deficiency (7) with a CVID-like clinical phenotype were enrolled in the study. Genomic DNA was extracted from peripheral blood and the molecular analysis of the TACI gene was performed by PCR (Polymerase Chain Reaction) and sequencing of all 5 exons, including exon–intron boundaries. Results: Seventeen patients (14.5%) displayed TACI defects, four (23.5%) carried combined heterozygous mutations and 13 (76.5%) carried single heterozygous mutations. The most frequently detected mutation was C104R (58.8%), followed by I87N (23.5%) and A181E (11.8%), while R20C, C62Y, P151L, K188M and E236X mutations were present in only one patient each. Patients with TACI defects were more frequently male (p = 0.011) and displayed a benign lymphoproliferation (splenomegaly and lymph node enlargement, p = 0.047 and p = 0.002, respectively), had a history of tonsillectomy (p = 0.015) and adenoidectomy (p = 0.031) and more frequently exhibited autoimmune cytopenias (p = 0.046). Conclusions: Considering that accumulating evidence suggests several CVID patients have a complex rather than a monogenic inheritance, our data further support the notion that TACI mutations, particularly as monoallelic defects, should be primarily considered as susceptibility co-factors and/or modifiers of primary antibody deficiencies.

TACI deficiency - a complex system out of balance

TACI promotes T-cell independent antibody responses and plasma cell differentiation and counteracts BAFF driven B-cell activation. Mutations in TNFRSF13B (encoding TACI) are associated with common variable immunodeficiency (CVID) but are also found in 1-2% of the general population. Although not diseases causing, certain TNFRSF13B mutations predispose CVID patients to autoimmunity and lymphoproliferation. Recently, studies of TACI-deficient humans and murine models revealed novel aspects of TACI, especially its crosstalk with the TLR pathways, differential expression of TACI isoforms, and its role in the generation of autoreactive B-cells. Vice versa, these studies are instrumental for a better understanding of TACI deficiency in humans and suggest that gene dosage, mutation type, and additional clinical or laboratory abnormalities influence the relevance of TNFRSF13B variants in individual CVID patients. TACI is embedded in a complex and well-balanced system, which is vulnerable to genetic and possibly also environmental hits.

Germinal Center and Extrafollicular B Cell Responses in Vaccination, Immunity, and Autoimmunity

Activated B cells participate in either extrafollicular (EF) or germinal center (GC) responses. Canonical responses are composed of a short wave of plasmablasts (PBs) arising from EF sites, followed by GC producing somatically mutated memory B cells (MBC) and long-lived plasma cells. However, somatic hypermutation (SHM) and affinity maturation can take place at both sites, and a substantial fraction of MBC are produced prior to GC formation. Infection responses range from GC responses that persist for months to persistent EF responses with dominant suppression of GCs. Here, we review the current understanding of the functional output of EF and GC responses and the molecular switches promoting them. We discuss the signals that regulate the magnitude and duration of these responses, and outline gaps in knowledge and important areas of inquiry. Understanding such molecular switches will be critical for vaccine development, interpretation of vaccine efficacy and the treatment for autoimmune diseases.

Late-onset and long-lasting autoimmune neutropenia: an analysis from the Italian Neutropenia Registry

Primary autoimmune neutropenia (pAN) is typified by onset in early infancy and a mild/moderate phenotype that resolves within 3 years of diagnosis. In contrast, secondary AN is classically an adult disease associated with malignancy, autoimmunity, immunodeficiency, viral infection, or drugs. This study describes a cohort of 79 children from the Italian Registry who, although resembling pAN, did not fully match the criteria for pAN because neutropenia either appeared after age 5 years (LO-Np) or lasted longer than 3 years (LL-Np). These 2 categories compared with classical pAN showed a far inferior rate of resolution (P < .001), lower severity of neutropenia (P = .03), leukopenia (P < .001), lymphopenia (P < .001) with low B+ (P = .001), increased need of granulocyte colony-stimulating factor (P = .04), and increased frequency of autoimmunity over the disease course (P < .001). A paired comparison between LO-Np and LL-Np suggested that LO-Np had a lower rate of resolution (P < .001) and lower white blood cell (P < .001) and lymphocyte (P < .001) values, higher occurrence of apthae (P = .008), and a stronger association with autoimmune diseases/markers (P = .001) than LL-Np, thus suggesting a more pronounced autoimmune signature for LO-Np. A next-generation sequencing panel applied in a small subgroup of LO-Np and LL-Np patients identified variants related to immune dysregulations. Overall, these findings indicate that there are important differences among pAN LL-Np and LO-Np. Forms rising after 3 years of age, with low tendency to resolution, require tight monitoring and extensive immune investigations aimed to early identify underlying immunologic disease.

Beyond monogenetic rare variants: tackling the low rate of genetic diagnoses in predominantly antibody deficiency

Predominantly antibody deficiency (PAD) is the most prevalent form of primary immunodeficiency, and is characterized by broad clinical, immunological and genetic heterogeneity. Utilizing the current gold standard of whole exome sequencing for diagnosis, pathogenic gene variants are only identified in less than 20% of patients. While elucidation of the causal genes underlying PAD has provided many insights into the cellular and molecular mechanisms underpinning disease pathogenesis, many other genes may remain as yet undefined to enable definitive diagnosis, prognostic monitoring and targeted therapy of patients. Considering that many patients display a relatively late onset of disease presentation in their 2nd or 3rd decade of life, it is questionable whether a single genetic lesion underlies disease in all patients. Potentially, combined effects of other gene variants and/or non-genetic factors, including specific infections can drive disease presentation. In this review, we define (1) the clinical and immunological variability of PAD, (2) consider how genetic defects identified in PAD have given insight into B-cell immunobiology, (3) address recent technological advances in genomics and the challenges associated with identifying causal variants, and (4) discuss how functional validation of variants of unknown significance could potentially be translated into increased diagnostic rates, improved prognostic monitoring and personalized medicine for PAD patients. A multidisciplinary approach will be the key to curtailing the early mortality and high morbidity rates in this immune disorder.

Update on Infections in Primary Antibody Deficiencies

Bacterial respiratory tract infections are the hallmark of primary antibody deficiencies (PADs). Because they are also among the most common infections in healthy individuals, PADs are usually overlooked in these patients. Careful evaluation of the history, including frequency, chronicity, and presence of other infections, would help suspect PADs. This review will focus on infections in relatively common PADs, discussing diagnostic challenges, and some management strategies to prevent infections.

B Cell Dysregulation in Common Variable Immunodeficiency Interstitial Lung Disease

Common variable immunodeficiency (CVID) is the most frequently diagnosed primary antibody deficiency. About half of CVID patients develop chronic non-infectious complications thought to be due to intrinsic immune dysregulation, including autoimmunity, gastrointestinal disease, and interstitial lung disease (ILD). Multiple studies have found ILD to be a significant cause of morbidity and mortality in CVID. Yet, the precise mechanisms underlying this complication in CVID are poorly understood. CVID ILD is marked by profound pulmonary infiltration of both T and B cells as well as granulomatous inflammation in many cases. B cell depletive therapy, whether done as a monotherapy or in combination with another immunosuppressive agent, has become a standard of therapy for CVID ILD. However, CVID is a heterogeneous disorder, as is its lung pathology, and the precise patients that would benefit from B cell depletive therapy, when it should administered, and how long it should be repeated all remain gaps in our knowledge. Moreover, some have ILD recurrence after B cell depletive therapy and the relative importance of B cell biology remains incompletely defined. Developmental and functional abnormalities of B cell compartments observed in CVID ILD and related conditions suggest that imbalance of B cell signaling networks may promote lung disease. Included within these potential mechanisms of disease is B cell activating factor (BAFF), a cytokine that is upregulated by the interferon gamma (IFN-γ):STAT1 signaling axis to potently influence B cell activation and survival. B cell responses to BAFF are shaped by the divergent effects and expression patterns of its three receptors: BAFF receptor (BAFF-R), transmembrane activator and CAML interactor (TACI), and B cell maturation antigen (BCMA). Moreover, soluble forms of BAFF-R, TACI, and BCMA exist and may further influence the pathogenesis of ILD. Continued efforts to understand how dysregulated B cell biology promotes ILD development and progression will help close the gap in our understanding of how to best diagnose, define, and manage ILD in CVID.

Primary Immunodeficiency and Thrombocytopenia

Primary immunodeficiency (PID) or Inborn errors of immunity (IEI) refers to a heterogeneous group of disorders characterized by immune system impairment. Although patients with IEI manifest highly variable symptoms, the most common clinical manifestations are recurrent infections, autoimmunity and malignancies. Some patients present hematological abnormality including thrombocytopenia due to different pathogenic mechanisms. This review focuses on primary and secondary thrombocytopenia as a complication, which can occur in IEI. Based on the International Union of Immunological Societies phenotypic classification for IEI, the several innate and adaptive immunodeficiency disorders can lead to thrombocytopenia. This review, for the first time, describes manifestation, mechanism and therapeutic modalities for thrombocytopenia in different classes of IEI.

Current genetic landscape in common variable immune deficiency

Using whole-exome sequencing to examine the genetic causes of immune deficiency in 235 common variable immunodeficiency (CVID) patients seen in the United States (Mount Sinai, New York), 128 patients from Sweden, and 208 from Iran revealed 68 known disease-causing genes underlying this heterogeneous immune defect. The patients at the time of study ranged from 4 to 90 years of age. Overall, 31%, 36%, and 54% of the patients in the US, Swedish, or Iranian cohorts had mutations. The multiplicity of genes identified in the 571 subjects reflects the complex requirements of B-cell antigen signaling, activation, survival, migration, maturation, and maintenance of antibody-secreting memory B-cell populations to the plasma cell stage. For the US and Swedish cohorts, CVID subjects with noninfectious complications, lymphoid infiltrations, inflamatory conditions, or autoimmunity were somewhat more likely to have an identifiable gene, but in both cohorts, numerous subjects with these medical conditions had no potential gene that could be assigned. Specific clinical patterns of illnesses were also not linked to any given gene defect as there was considerable overlap in clinical presentations. These observations led to a new perspective on the complexity of the immunologic phenotype found in CVID syndrome.

Identifying and treating refractory ITP: difficulty in diagnosis and role of combination treatment

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia after chemotherapy-induced thrombocytopenia. Existing guidelines describe the management and treatment of most patients who, overall, do well, even if they present with chronic disease, and they are usually not at a high risk for bleeding; however, a small percentage of patients is refractory and difficult to manage. Patients classified as refractory have a diagnosis that is not really ITP or have disease that is difficult to manage. ITP is a diagnosis of exclusion; no specific tests exist to confirm the diagnosis. Response to treatment is the only affirmative confirmation of diagnosis. However, refractory patients do not respond to front-line or other treatments; thus, no confirmation of diagnosis exists. The first section of this review carefully evaluates the diagnostic considerations in patients with refractory ITP. The second section describes combination treatment for refractory cases of ITP. The reported combinations are divided into the era before thrombopoietin (TPO) and rituximab and the current era. Current therapy appears to have increased effectiveness. However, the definition of refractory, if it includes insufficient response to TPO agents, describes a group with more severe and difficult-to-treat disease. The biology of refractory ITP is largely unexplored and includes oligoclonality, lymphocyte pumps, and other possibilities. Newer treatments, especially rapamycin, fostamatinib, FcRn, and BTK inhibitors, may be useful components of future therapy given their mechanisms of action; however, TPO agents, notwithstanding failure as monotherapy, appear to be critical components. In summary, refractory ITP is a complicated entity in which a precise specific diagnosis is as important as the development of effective combination treatments.

Non-infectious Complications of Common Variable Immunodeficiency: Updated Clinical Spectrum, Sequelae, and Insights to Pathogenesis

Non-infectious complications in common variable immunodeficiency (CVID) have emerged as a major clinical challenge. Detailed clinical spectrum, organ-specific pathologies and associated sequelae from 623 CVID patients followed in New York since 1974 were analyzed, and recent insights to pathogenesis were reviewed. Non-infectious manifestations were present in 68.1% of patients, and they do not tend to be present in isolation. They include autoimmunity (33.2%), chronic lung disease (30.3%), lymphoid hyperplasia/splenomegaly (20.9%), liver disease (12.7%), granulomas (9.3%), gastrointestinal disease (7.3%), lymphoma (6.7%), and other malignancies (6.4%). In the lungs, interstitial disease and bronchiectasis were the most common findings, with lymphoma at this site being a rare (n = 6), but serious, manifestation. Bronchiectasis was not a prerequisite for the development of interstitial disease. In the liver, granulomas and nodular regenerative hyperplasia were the most common. Gastrointestinal disease may affect any segment of the intestinal tract, with lymphoid infiltrations and villous blunting being the leading histologic findings. With progression of organ-specific diseases, a wide spectrum of associated sequelae was observed. Lymphoma was more common in females (P = 0.036)—all B cell types except in one subject. Solid organ transplantations (liver, n = 5; lung, n = 4; combined lung and heart, n = 2) and hematopoietic stem cell transplantations (for B cell lymphoma, n = 1) have rarely been performed in this cohort, with mixed outcomes. Recent identification of monogenic defects, in ~10–30% of various CVID cohorts, has highlighted the molecular pathways that can affect both antibody production and broader immune regulation. In addition, cellular defects in both innate and adaptive immune systems are increasingly recognized in this syndrome.

What did we learn from CTLA-4 insufficiency on the human immune system?

Cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) is a negative immune regulator constitutively expressed on regulatory T (Treg) cells and upregulated on activated T cells. CTLA-4 inhibits T cell activation by various suppressive functions including competition with CD28, regulation of the inhibitory function of Treg cells, such as transendocytosis, and the control of adhesion and motility. Intrinsic CTLA-4 signaling has been controversially discussed, but so far no distinct signaling pathway has been identified. The CTLA-4-mediated Treg suppression plays an important role in the maintenance of peripheral tolerance and the prevention of autoimmune diseases. Human CTLA-4 insufficiency is caused by heterozygous germline mutations in CTLA4 and characterized by a complex immune dysregulation syndrome. Clinical studies on CTLA4 mutation carriers showed a reduced penetrance and variable expressivity, suggesting modifying factor(s). One hundred and forty-eight CTLA4 mutation carriers have been reported; patients showed hypogammaglobulinemia, recurrent infectious diseases, various autoimmune diseases, and lymphocytic infiltration into multiple organs. The CTLA-4 expression level in Treg cells was reduced, while the frequency of Treg cells was increased in CTLA-4-insufficient patients. The transendocytosis assay is a specific functional test for the assessment of newly identified CTLA4 gene variants. Immunoglobulin substitution, corticosteroids, immunosuppressive therapy, and targeted therapy such as with CTLA-4 fusion proteins and mechanistic target of rapamycin (mTOR) inhibitors were applied; patients with life-threatening, treatment-resistant symptoms underwent hematopoietic stem cell transplantation. The fact that in humans CTLA-4 insufficiency causes severe disease taught us that the amount of CTLA-4 molecules present in/on T cells matters for immune homeostasis. However, whether the pathology-causing activated T lymphocytes in CTLA-4-insufficient patients are antigen-specific is an unsolved question. CTLA-4, in addition, has a role in autoimmune diseases and cancer. Anti-CTLA-4 drugs are employed as checkpoint inhibitors to target various forms of cancer. Thus, clinical research on human CTLA-4 insufficiency might provide us a deeper understanding of the mechanism(s) of the CTLA-4 molecule and immune dysregulation disorders.

Idiopathic, Refractory Sweet's Syndrome Associated with Common Variable Immunodeficiency: a Case Report and Literature Review

PURPOSE OF REVIEW

Sweet's syndrome (SS) is classically considered a hypersensitivity reaction often associated with autoimmune disorders and malignancy. SS has also been increasingly reported to occur with immunodeficiencies. We present a case of treatment-refractory, systemic SS as the initial manifestation in a young child with common variable immunodeficiency (CVID). We also review current literature about SS and concurrent immunodeficiencies and autoimmunity in CVID patients.

RECENT FINDINGS

Few case reports exist regarding the co-occurrence of Sweet's syndrome and primary immunodeficiencies. SS is characterized by a pro-inflammatory state with a neutrophil predominance resulting in a spectrum of clinical manifestations. CVID is a multifactorial antibody deficiency that can be associated with autoimmunity, which some studies have proposed to be secondary to altered CD21 expression. SS occurring in patients with CVID has been infrequently reported, and one case study demonstrated improvement of Sweet's associated skin lesions with immunoglobulin replacement. In our case, the patient had multi-system SS refractory to multiple immunomodulatory therapies. To our knowledge, this is the first report of the effective and safe use of intravenous tocilizumab and oral lenalidomide to treat SS in a child with CVID. Immunoglobulin replacement reduced the frequency of infections and may have contributed to the opportunity to wean the immunosuppressive therapies for Sweet's syndrome. Sweet's syndrome as an initial manifestation of co-occurring immunodeficiencies is rare, and providers need a high index of suspicion. In addition, treatment of SS associated with an immunodeficiency can be a challenge. Treatment with immunoglobulin replacement reduces the frequency of infections, and in some patients with concurrent SS may improve skin lesions and reduce the need for immunomodulator therapy. Further study is necessary to better understand the pathogenesis of CVID in patients with SS and to identify possible biomarkers that predict who with SS are at risk for developing hypogammaglobulinemia.

BAFF-driven B cell hyperplasia underlies lung disease in common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency and is frequently complicated by interstitial lung disease (ILD) for which etiology is unknown and therapy inadequate.

METHODS

Medical record review implicated B cell dysregulation in CVID ILD progression. This was further studied in blood and lung samples using culture, cytometry, ELISA, and histology. Eleven CVID ILD patients were treated with rituximab and followed for 18 months.

RESULTS

Serum IgM increased in conjunction with ILD progression, a finding that reflected the extent of IgM production within B cell follicles in lung parenchyma. Targeting these pulmonary B cell follicles with rituximab ameliorated CVID ILD, but disease recurred in association with IgM elevation. Searching for a stimulus of this pulmonary B cell hyperplasia, we found B cell-activating factor (BAFF) increased in blood and lungs of progressive and post-rituximab CVID ILD patients and detected elevation of BAFF-producing monocytes in progressive ILD. This elevated BAFF interacts with naive B cells, as they are the predominant subset in progressive CVID ILD, expressing BAFF receptor (BAFF-R) within pulmonary B cell follicles and blood to promote Bcl-2 expression. Antiapoptotic Bcl-2 was linked with exclusion of apoptosis from B cell follicles in CVID ILD and increased survival of naive CVID B cells cultured with BAFF.

CONCLUSION

CVID ILD is driven by pulmonary B cell hyperplasia that is reflected by serum IgM elevation, ameliorated by rituximab, and bolstered by elevated BAFF-mediated apoptosis resistance via BAFF-R.

FUNDING

NIH, Primary Immune Deficiency Treatment Consortium, and Rare Disease Foundation.

Rare TACI Mutation in a 3-Year-Old Boy With CVID Phenotype

Common variable immunodeficiency (CVID) is the most common and clinically relevant primary immunodeficiency (PID). Genetic basis of CVID remains largely unknown. However, in a minority of CVID patients, a number of distinct genetic defects affecting the normal processes of B cell maturation and differentiation into memory B cells have now been identified, resulting in markedly reduced serum levels of immunoglobulin G (IgG) and low immunoglobulin A (IgA) or immunoglobulin M (IgM), with impaired antibody responses, despite the presence of normal levels of B cells. Patients with CVID develop recurrent and chronic infections of respiratory and gastrointestinal tracts, autoimmune diseases, lymphoproliferative complications, malignancies, and granulomatous disease. We report the case of a boy admitted to our unit for the first time at the age of three for reduced gamma globulin levels and a clinical history positive for two episodes of pneumonia. Our patient incompletely met ESID diagnostic criteria for CVID, but molecular genetic analysis, a NGS panel including 47 PID-associated genes was performed in the proband and in his parents, revealing the presence of a heterozygous nucleotide substitution in exon 4 (c.579C>A) of TNFRSF13B encoding TACI. This mutation has been described only in two CVID adult patients and in a child with selective IgA deficiency (sIgAD). We highlighted the same mutation in the asymptomatic mother and detected two extra heterozygous mutations of RIG1 and LIG1. We promptly started intravenous immunoglobulin (IVIG) therapy with good tolerance. Despite the diagnosis of CVID remains clinical, in this case report we underline the importance of considering and planning genetic workup in all subjects with unclear diagnosis and of reporting new molecular diagnosis especially in case of rare mutations.

Common variable immune deficiency: Dissection of the variable

Starting about 60 years ago, a number of reports appeared that outlined the severe clinical course of a few adult subjects with profound hypogammaglobinemia. Puzzled by the lack of family history and adult onset of symptoms in most, the name "acquired" hypogammaglobinemia was given, but later altered to the current name common variable immune deficiency. Pathology reports remarked on the loss of lymph node architecture and paucity of plasma cells in lymphoid tissues in these subjects. While characterized by reduced serum IgG and IgA and often IgM, and thus classified among the B-cell defects, an increasing number of cellular defects in these patients have been recognized over time. In the early years, severe respiratory tract infections commonly led to a shortened life span, but the wide spread availability of immune globulin concentrates for the last 25 years has improved survival. However, chronic non-infectious inflammatory and autoimmune conditions have now emerged as challenging clinical problems; these require further immunologic understanding and additional therapeutic measures. Recent study of this phenotypic syndrome have provided an increasingly fertile ground for the identification of autosomal recessive and now more commonly, autosomal dominant gene defects which lead to the loss of B-cell development in this syndrome.

Primary B-cell immunodeficiencies

Primary B-cell immunodeficiencies refer to diseases resulting from impaired antibody production due to either molecular defects intrinsic to B-cells or a failure of interaction between B-cells and T-cells. Patients typically have recurrent infections and can vary with presentation and complications depending upon where the defect has occurred in B-cell development or the degree of functional impairment. In this review, we describe B-cell specific immune defects categorized by presence or absence of peripheral B-cells, immunoglobulins isotypes and evidence of antibody impairment.

TACI Isoforms Regulate Ligand Binding and Receptor Function

TACI signals activate B cell proliferation, isotype switch and antibody production in both normal immunity and autoimmune states. In contrast to murine TACI, the human TACI gene undergoes alternative splicing to produce short and long isoforms (TACI-S and TACI-L). In previous studies, we showed that transduction of the short, but not long isoform, into murine B cells or human pre-B cells lacking TACI, caused them to become transcriptional and morphologically identical to plasma cells. These data suggest that the expression of different isoforms in humans provides unique controls on B cell maturation. In these studies we show that TACI-S and TACI-L form complexes in a ligand-independent manner, not dependent on a single extracellular domain. Both TACI isoforms are detectable in the endosomal cellular compartment where they co-localize with MyD88, TRAF6, and the activated 65 kDa form of TLR9, depending on a conserved intracellular TACI sequence. In contrast to TACI-L expressing cells, or cells bearing both isoforms, TACI-S binds ligands BAFF and APRIL with substantially greater affinity and promotes enhanced NF-kB activation. Using isoform-specific monoclonal antibodies, we show that while TACI-L is predominant as a surface receptor surface on human B cells, significantly more TACI-S is noted in the intracellular compartment and also in marginal zone, isotype switched and plasmablast in resting B cells. TACI-S is increased in tonsillar B cells and also in the intracellular compartment of activated peripheral B cells. These data shows that alternative splicing of the human TACI gene leads to two isoforms both of which intersect with MyD88 and TRAF6 and form complexes with TLR9, but the two isoforms have different ligand binding capacities, subcellular locations and activation capabilities.

Diagnostic Tools for Inborn Errors of Human Immunity (Primary Immunodeficiencies and Immune Dysregulatory Diseases)

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of diagnostic testing in primary immunodeficiency and immune dysregulatory disorders (PIDDs), particularly focusing on flow cytometry and genetic techniques, utilizing specific examples of PIDDs.

RECENT FINDINGS

Flow cytometry remains a vital tool in the diagnosis and monitoring of immunological diseases. Its utility ranges from cellular analysis and specific protein quantitation to functional assays and signaling pathway analysis. Mass cytometry combines flow cytometry and mass spectrometry to dramatically increase the throughput of multivariate single-cell analysis. Next-generation sequencing in combination with other molecular techniques and processing algorithms has become more widely available and identified the diverse and heterogeneous genetic underpinnings of these disorders. As the spectrum of disease is further clarified by increasing immunological, genetic, and epigenetic knowledge, the careful application of these diagnostic tools and bioinformatics will assist not only in our understanding of these complex disorders, but also enable the implementation of personalized therapeutic approaches for disease management.

A gain-of-function mutation in TNFRSF13B is a candidate for predisposition to familial or sporadic immune thrombocytopenia

Essentials Positive family histories suggest the existence of hereditary immune thrombocytopenia (ITP). The predisposing gene for familial ITP was screened in two familial ITP patients. The G76S mutation on TNFRSF13B led to immune dysfunction and induced megakaryocyte apoptosis. The G76S mutation on TNFRSF13B is a gain-of-function mutation and a predisposing variant for ITP.

SUMMARY

Background Most immune thrombocytopenia (ITP) is sporadic but a positive family history of ITP in some patients suggests that hereditary forms exist. Because of the rarity of familial ITP families available for study and the heterogeneity of sporadic ITP, family linkage analysis or genome-wide association studies are limited. Objectives Based on one ITP pedigree, we try to identify the predisposing gene in familial or sporadic ITP and reveal the way in which it causes thrombocytopenia. Methods Gene expression profiling analysis and whole-exome sequencing were performed on samples from family members with ITP, sporadic ITP cases and healthy individuals. We also evaluated the influence of potential pathogenic mutation on immune function and megakaryocyte apoptosis. Results Whole-exome sequencing identified a potential pathologic p.G76S heterozygous mutation on the TNFRSF13B gene in familial ITP patients. ITP patients harboring the G76S mutation displayed an upregulated 'cytokine-cytokine receptor interaction' signal, increased serum TNFα, IL-17α, IFNγ and BAFF levels, and enhanced binding capacity of APRIL ligand to B cells. Additionally, Epstein-Barr virus (EBV)-transformed B cells with the G76S mutation could induce human megakaryocyte line (Meg-01) apoptosis significantly. Conclusion p.G76S mutation on the TNFRSF13B gene is responsible for ITP, and is a genetic predisposing factor for familial or sporadic ITP.

Dysregulation of Innate Lymphoid Cells in Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is the most prevalent symptomatic primary immune deficiency. With widespread use of immunoglobulin replacement therapy, non-infectious complications, such as autoimmunity, chronic intestinal inflammation, and lung disease, have replaced infections as the major cause of morbidity and mortality in this immune deficiency. The pathogenic mechanisms that underlie the development of these complications in CVID are not known; however, there have been numerous associated laboratory findings. Among the most intriguing of these associations is elevation of interferon signature genes in CVID patients with inflammatory/autoimmune complications, as a similar gene expression profile is found in systemic lupus erythematosus and other chronic inflammatory diseases. Linked with this heightened interferon signature in CVID is an expansion of circulating IFN-γ-producing innate lymphoid cells. Innate lymphoid cells are key regulators of both protective and pathogenic immune responses that have been extensively studied in recent years. Further exploration of innate lymphoid cell biology in CVID may uncover key mechanisms underlying the development of inflammatory complications in these patients and may inspire much needed novel therapeutic approaches.

Autoimmune and Lymphoproliferative Complications of Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is frequently complicated by the development of autoimmune and lymphoproliferative diseases. With widespread use of immunoglobulin replacement therapy, autoimmune and lymphoproliferative complications have replaced infection as the major cause of morbidity and mortality in CVID patients. Certain CVID complications, such as bronchiectasis, are likely to be the result of immunodeficiency and are associated with infection susceptibility. However, other complications may result from immune dysregulation rather than immunocompromise. CVID patients develop autoimmunity, lymphoproliferation, and granulomas in association with distinct immunological abnormalities. Mutations in transmembrane activator and CAML interactor, reduction of isotype-switched memory B cells, expansion of CD21 low B cells, heightened interferon signature expression, and retained B cell function are all associated with both autoimmunity and lymphoproliferation in CVID. Further research aimed to better understand that the pathological mechanisms of these shared forms of immune dysregulation may inspire therapies beneficial for multiple CVID complications.

Autoimmunity and infection in common variable immunodeficiency (CVID)

Common variable immunodeficiency (CVID) is a heterogeneous group of diseases, characterized by primary hypogammaglobulinemia. B and T cell abnormalities have been described in CVID. Typical clinical features of CVID are recurrent airway infections; lymphoproliferative, autoinflammatory, or neoplastic disorders; and autoimmune diseases among which autoimmune thrombocytopenia (ITP) is the most common. The coexistence of immunodeficiency and autoimmunity appears paradoxical, since one represents a hypoimmune state and the other a hyperimmune state. Considering both innate and adaptive immune response abnormalities in CVID, it is easier to understand the mechanisms that lead to a breakdown of self-tolerance. CD21(low) B cells derive from mature B cells that have undergone chronic immune stimulation; they are increased in CVID patients. The expansion of CD21(low) B cells is also observed in certain autoimmune diseases. We have studied CD21(low) B cells in patients with CVID, CVID, and ITP and with ITP only. We observed a statistically significant increase in the CD21(low) population in the three pathological groups. Moreover, we found statistical differences between the two groups of CVID patients: patients with ITP had a higher percentage of CD21(low) cells. Our data suggest that CD21(low) cells are related to autoimmunity and may represent a link between infection and autoimmunity.

Evaluation of cytokine genetic polymorphisms in adult patients with common variable immunodeficiency: A single-center study

Common variable immunodeficiency (CVID) is a heterogeneous disease characterized by impaired B-cell differentiation and maturation accompanied with the defective antibody production. Several investigators addressed the possibility that disturbed cytokine production of TNF, IL-6, IFN-γ and IL-10, among a variety of others, may be implicated in CVID. The aim of this study was to test the hypothesis that genetic polymorphisms involving TNF (-308G/A), IFNG (+874 T/A), IL10 (-1082G/A, -819T/C and -592A/C), and IL6 (-174G/C) cytokine genes might contribute to susceptibility to CVID. Thirty five patients with CVID and 250 healthy controls were genotyped for indicated single nucleotide polymorphisms (SNP) in TNF, IL6, IFNG and IL10 using Taqman-based assays. CVID patients had significantly higher frequency of TNF A allele and AA genotype than in healthy subjects (p=0.006; OR=2.27; 95%CI=1.24-4.17 and p=0.038, OR=15.64; 95%CI=1.38-177.20, respectively). In addition, the frequency of GG genotype was significantly higher in healthy controls than in patient group (p=0.019, OR=0.43, 95%CI=0.21-0.89). Genetic analysis of IL6 SNP showed that allele G confers increased risk for CVID (p=0.037, OR=1.78, 95% CI=1.03-3.08) while IFNG allele T was associated with splenomegaly in CVID (p=0.032; OR=2.86; 95% CI=1.08-7.56). We observed no association between genotypes, alleles and haplotypes of IL-10 gene and CVID or its clinical complications. In conclusion, our results indicated association between CVID and cytokine gene polymorphisms -308G/A TNF and -174G/C IL6. In addition, we demonstrated that splenomegaly, one of the most common complications in this disease, is associated with +874T/A IFNG polymorphism. These findings add further support to the notion that cytokines may play significant role in pathogenesis of this primary antibody deficiency. However, further investigation that would involve a larger study group of CVID patients is warranted to confirm our findings.

Rare autoimmune disorders with Mendelian inheritance

Autoimmune diseases represent a heterogeneous group of common disorders defined by complex trait genetics and environmental effects. The genetic variants usually align in immune and metabolic pathways that affect cell survival or apoptosis and modulate leukocyte function. Nevertheless, the exact triggers of disease development remain poorly understood and the current therapeutic interventions only modify the disease course. Both the prevention and the cure of autoimmune disorders are beyond our present medical capabilities. In contrast, a growing number of single gene autoimmune disorders have also been identified and characterized in the last few decades. Mutations and other gene alterations exert significant effects in these conditions, and often affect genes involved in central or peripheral immunologic tolerance induction. Even though a single genetic abnormality may be the disease trigger, it usually upsets a number of interactions among immune cells, and the biological developments of these monogenic disorders are also complex. Nevertheless, identification of the triggering molecular abnormalities greatly contributes to our understanding of the pathogenesis of autoimmunity and facilitates the development of newer and more effective treatment strategies.

T-cell abnormalities in common variable immunodeficiency: the hidden defect

This review discusses how the T-cell compartment in common variable immunodeficiency is marked by the premature arrest in thymic output, leading to T-cell exhaustion and immune dysregulation. Although B cells have been the main focus of the disorder, ample experimental data suggest that T-cell abnormalities can be seen in a large proportion of Freiburg Group 1a patients and those suffering from inflammatory complications. The reductions in T-cell receptor excision circles, naïve T cells, invariant NKT cells and regulatory T cells suggest a diminished thymic output, while CD8 T cells are driven towards exhaustion either via an antigen-dependent or an antigen-independent manner. The theoretical risk of anti-T-cell therapies is discussed, highlighting the need for an international effort in generating longitudinal data in addition to better-defined underlying molecular characterisation.

Immunoglobulin-induced hemolysis, splenomegaly and inflammation in patients with antibody deficiencies

IgG replacement for primary antibody deficiencies is a safe treatment administered to prevent recurrent infections and reduce mortality. Recently, several reports described acute hemolytic episodes following IgG administration due to a passive transfer of blood group alloantibodies, including anti-A, anti-B, as well as anti-Rh antibodies. Here, we reviewed and discussed the consequences of passively transferred RBCs antibodies. The chronic passive transfer of alloantibodies might also cause a subclinical condition due to a compensated extravascular chronic hemolysis with poorly understood consequences. This phenomenon might possibly represent an unrecognized cause of splenomegaly and might contribute to inflammation in patients with primary antibody deficiencies.

Clinical and laboratory correlates of lung disease and cancer in adults with idiopathic hypogammaglobulinaemia

Idiopathic hypogammaglobulinaemia, including common variable immune deficiency (CVID), has a heterogeneous clinical phenotype. This study used data from the national UK Primary Immune Deficiency (UKPID) registry to examine factors associated with adverse outcomes, particularly lung damage and malignancy. A total of 801 adults labelled with idiopathic hypogammaglobulinaemia and CVID aged 18-96 years from 10 UK cities were recruited using the UKPID registry database. Clinical and laboratory data (leucocyte numbers and serum immunoglobulin concentrations) were collated and analysed using uni- and multivariate statistics. Low serum immunoglobulin (Ig)G pre-immunoglobulin replacement therapy was the key factor associated with lower respiratory tract infections (LRTI) and history of LRTI was the main factor associated with bronchiectasis. History of overt LRTI was also associated with a significantly shorter delay in diagnosis and commencing immunoglobulin replacement therapy [5 (range 1-13 years) versus 9 (range 2-24) years]. Patients with bronchiectasis started immunoglobulin replacement therapy significantly later than those without this complication [7 (range 2-22) years versus 5 (range 1-13) years]. Patients with a history of LRTI had higher serum IgG concentrations on therapy and were twice as likely to be on prophylactic antibiotics. Ensuring prompt commencement of immunoglobulin therapy in patients with idiopathic hypogammaglobulinaemia is likely to help prevent LRTI and subsequent bronchiectasis. Cancer was the only factor associated with mortality. Overt cancer, both haematological and non-haematological, was associated with significantly lower absolute CD8(+) T cell but not natural killer (NK) cell numbers, raising the question as to what extent immune senescence, particularly of CD8(+) T cells, might contribute to the increased risk of cancers as individuals age.

Toll-like receptor signaling in primary immune deficiencies

Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency.

TNF receptor superfamily member 13b (TNFRSF13B) hemizygosity reveals transmembrane activator and CAML interactor haploinsufficiency at later stages of B-cell development

BACKGROUND

Heterozygous C104R or A181E TNF receptor superfamily member 13b (TNFRSF13B) mutations impair removal of autoreactive B cells, weaken B-cell activation, and convey to patients with common variable immune deficiency (CVID) an increased risk for autoimmunity. How mutant transmembrane activator and CAML interactor (TACI) influences wild-type TACI function is unclear; different models suggest either a dominant negative effect or haploinsufficiency.

OBJECTIVE

We investigated potential TACI haploinsufficiency by analyzing patients with antibody-deficient Smith-Magenis syndrome (SMS) who possess only 1 TNFRSF13B allele and antibody-deficient patients carrying one c.204insA TNFRSF13B null mutation.

METHODS

We tested the reactivity of antibodies isolated from single B cells from patients with SMS and patients with a c.204insA TNFRSF13B mutation and compared them with counterparts from patients with CVID with heterozygous C104R or A181E TNFRSF13B missense mutations. We also assessed whether loss of a TNFRSF13B allele induced haploinsufficiency in naive and memory B cells and recapitulated abnormal immunologic features typical of patients with CVID with heterozygous TNFRSF13B missense mutations.

RESULTS

We found that loss of a TNFRSF13B allele does not affect TACI expression, activation responses, or establishment of central B-cell tolerance in naive B cells. Additionally, patients with SMS and those with a c.204insA TNFRSF13B mutation display normal regulatory T-cell function and peripheral B-cell tolerance. The lack of a TNFRSF13B allele did result in decreased TACI expression on memory B cells, resulting in impaired activation and antibody secretion.

CONCLUSION

TNFRSF13B hemizygosity does not recapitulate autoimmune features of CVID-associated C104R and A181E TNFRSF13B mutations, which likely encode dominant negative products, but instead reveals selective TACI haploinsufficiency at later stages of B-cell development.

Autoimmunity and Immune Dysregulation in Primary Immune Deficiency Disorders

Primary immune deficiencies are often associated with autoimmune disease due to the dysregulation of the immune system as a whole. In many immune deficiencies, lymphocytes may be present but dysfunctional, allowing for the development of excessive autoreactivity and resultant autoimmune disease. Autoimmune polyendocrinopathy candidiasis and ectodermal dystrophy, autoimmune lymphoproliferative syndrome, immunodyregulation polyendocrinopathy enteropathy X-linked, IL-10/IL-10 receptor deficiencies, and PLCG2-associated antibody deficiency and immune dysregulation are disorders in which autoimmunity is a hallmark of the clinical disease presentation. In contrast, adaptive and innate immune deficiencies, which are typically defined by their infectious susceptibilities, can be associated with variable rates of autoimmune manifestations, predominantly autoimmune cytopenias. This review describes the immune dysregulation and autoimmune manifestations that may be encountered in various immune deficiencies.

IgH sequences in common variable immune deficiency reveal altered B cell development and selection

Common variable immune deficiency (CVID) is the most common symptomatic primary immune deficiency, affecting ~1 in 25,000 persons. These patients suffer from impaired antibody responses, autoimmunity, and susceptibility to lymphoid cancers. To explore the cellular basis for these clinical phenotypes, we conducted high-throughput DNA sequencing of immunoglobulin heavy chain gene rearrangements from 93 CVID patients and 105 control subjects and sorted naïve and memory B cells from 13 of the CVID patients and 10 of the control subjects. The CVID patients showed abnormal VDJ rearrangement and abnormal formation of complementarity-determining region 3 (CDR3). We observed a decreased selection against antibodies with long CDR3s in memory repertoires and decreased variable gene replacement, offering possible mechanisms for increased patient autoreactivity. Our data indicate that patient immunodeficiency might derive from both decreased diversity of the naïve B cell pool and decreased somatic hypermutation in memory repertoires. The CVID patients also exhibited an abnormal clonal expansion of unmutated B cells relative to the controls. Although impaired B cell germinal center activation is commonly viewed as causative in CVID, these data indicate that CVID B cells diverge from controls as early as the pro-B stage, cell and suggest possible explanations for the increased incidence of autoimmunity, immunodeficiency, and lymphoma CVID patients.

Immunodeficiency in Chronic Sinusitis: Recognition and Treatment

Chronic rhinosinusitis (CRS) is estimated to affect over 35 million people. However, not all patients with the diagnosis respond to standard medical and surgical treatments. Although there are a variety of reasons a patient may be refractory to therapy, one possible etiology is the presence of an underlying immunodeficiency. This review will focus on the description, recognition, and treatment of several antibody deficiencies associated with CRS, including common variable immunodeficiency (CVID), selective IgA deficiency, IgG subclass deficiency, and specific antibody deficiency (SAD). The diagnosis of antibody deficiency in patients with CRS is important because of the large clinical implications it can have on sinus disease management. CVID is treated with immunoglobulin replacement, whereas SAD may be managed symptomatically and sometimes with prophylactic antibiotics and/or immunoglobulin replacement.

Lymphoproliferative disease and cancer among patients with common variable immunodeficiency

Innate immune deficiencies are a heterogeneous group of genetically inherited diseases affecting the innate and adaptive immune systems that confer susceptibility to infection, autoimmunity, and cancer. This review discusses the latest insights into the links between common variable immunodeficiency (CVI) and malignancies. Although Ig therapy greatly reduces the number of infections and enhances survival, it does not appear to address the development of cancer, especially lymphoma. The reasons for the increased susceptibility to lymphoid malignancies are unclear. These include genetics, immune dysregulation, radiosensitivity and chronic infections such as Helicobacter pylori, EBV, human herpes virus type 8 and cytomegalovirus. Further studies will allow us to better stratify the risk for cancer in these patients, and teach us to better prevent these complications and to better treat them.