Hyper immunoglobulin M syndrome due to CD40 deficiency: clinical, molecular, and immunological features

Prolonged pediatric intensive care unit (PICU) admission, challenges in diagnosis and treatment in a child with hyper IgM syndrome in a tertiary hospital in Tanzania: a case report

Hyper immunoglobulin M (IgM) syndromes are a collection of uncommon primary combined immunodeficiency disorders. They are characterized by recurrent bacterial infections due to low levels of IgG, IgA, and IgE, while IgM levels remain normal or high. These conditions stem from a mutation in the CD40 ligand gene or disruptions in the CD40-signaling pathway. Those affected face increased susceptibility to frequent bacterial infections, an elevated likelihood of autoimmune issues, and early-onset malignancies. These syndromes are rare and account for a small fraction of immunodeficiency cases. We describe a case of an African infant, who had a prolonged pediatric intensive care unit admission due to recurrent and severe infections which took a prolonged course of medication to be treated. After a diagnostic workup, a diagnosis of X-linked hyper IgM syndrome was established, and currently, our child is on monthly replacement of IV immunoglobulin and daily prophylactic cotrimoxazole tablets. Early diagnosis of primary immunodeficiency disorders reduces the incidence of infections and the severity of complications. This case demonstrates the consequences of delayed diagnosis and resulting in a prolonged hospital stay.

Transcriptional regulation of Tfh dynamics and the formation of immunological synapses

Inside germinal centers (GCs), antigen-specific B cells rely on precise interactions with immune cells and strategic localization between the dark and light zones to clonally expand, undergo affinity maturation, and differentiate into long-lived plasma cells or memory B cells. Follicular helper T (Tfh) cells, the key gatekeepers of GC-dependent humoral immunity, exhibit remarkable dynamic positioning within secondary lymphoid tissues and rely on intercellular interactions with antigen-presenting cells (APCs) during their differentiation and execution of B-cell-facilitating functions within GCs. In this review, we briefly cover the transcriptional regulation of Tfh cell differentiation and function and explore the molecular mechanisms governing Tfh cell motility, their interactions with B cells within GCs, and the impact of their dynamic behavior on humoral responses.

Clinical and Immunological Features, Genetic Variants, and Outcomes of Patients with CD40 Deficiency

PURPOSE

Inherited deficiencies of CD40 and CD40 ligand (CD40L) reflect the crucial immunological functions of CD40-CD40L interaction/signaling. Although numerous studies have provided a detailed description of CD40L deficiency, reports of CD40 deficiency are scarce. Herein, we describe the characteristics of all reported patients with CD40 deficiency.

METHODS

The PubMed, Embase and Web of Science databases were searched for relevant literature published till 7th August 2023. Study deduplication and identification of relevant reports was performed using the online PICO Portal. The data were extracted using a pre-designed data extraction form and the SPSS software was used for analysis.

RESULTS

Systematic literature review revealed 40 unique patients with CD40 deficiency. Respiratory tract and gastrointestinal infections were the predominant clinical manifestations (observed in 93% and 57% patients, respectively). Sclerosing cholangitis has been reported in nearly one-third of patients. Cryptosporidium sp. (29%) and Pneumocystis jirovecii (21%) were the most common microbes identified. Very low to undetectable IgG levels and severely reduced/absent switch memory B cells were observed in all patients tested/reported. Elevated IgM levels were observed in 69% patients. Overall, splice-site and missense variants were the most common (36% and 32%, respectively) molecular defects identified. All patients were managed with immunoglobulin replacement therapy and antimicrobial prophylaxis was utilized in a subset. Hematopoietic stem cell transplantation (HSCT) has been performed in 45% patients (curative outcome observed in 73% of these patients). Overall, a fatal outcome was reported in 21% patients.

CONCLUSIONS

We provide a comprehensive description of all important aspects of CD40 deficiency. HSCT is a promising curative treatment option for CD40 deficiency.

The off-target effects of AID in carcinogenesis

Activation-induced cytidine deaminase (AID) plays a crucial role in promoting B cell diversification through somatic hypermutation (SHM) and class switch recombination (CSR). While AID is primarily associated with the physiological function of humoral immune response, it has also been linked to the initiation and progression of lymphomas. Abnormalities in AID have been shown to disrupt gene networks and signaling pathways in both B-cell and T-cell lineage lymphoblastic leukemia, although the full extent of its role in carcinogenesis remains unclear. This review proposes an alternative role for AID and explores its off-target effects in regulating tumorigenesis. In this review, we first provide an overview of the physiological function of AID and its regulation. AID plays a crucial role in promoting B cell diversification through SHM and CSR. We then discuss the off-target effects of AID, which includes inducing mutations of non-Igs, epigenetic modification, and the alternative role as a cofactor. We also explore the networks that keep AID in line. Furthermore, we summarize the off-target effects of AID in autoimmune diseases and hematological neoplasms. Finally, we assess the off-target effects of AID in solid tumors. The primary focus of this review is to understand how and when AID targets specific gene loci and how this affects carcinogenesis. Overall, this review aims to provide a comprehensive understanding of the physiological and off-target effects of AID, which will contribute to the development of novel therapeutic strategies for autoimmune diseases, hematological neoplasms, and solid tumors.

Assessment of Enterovirus Excretion and Identification of VDPVs in Patients with Primary Immunodeficiency in India: Outcome of ICMR-WHO Collaborative Study Phase-I

The emergence of vaccine-derived polioviruses (VDPVs) in patients with Primary Immunodeficiency (PID) is a threat to the polio-eradication program. In a first of its kind pilot study for successful screening and identification of VDPV excretion among patients with PID in India, enteroviruses were assessed in stool specimens of 154 PID patients across India in a period of two years. A total of 21.42% of patients were tested positive for enteroviruses, 2.59% tested positive for polioviruses (PV), whereas 18.83% of patients were positive for non-polio enteroviruses (NPEV). A male child of 3 years and 6 months of age diagnosed with Hyper IgM syndrome was detected positive for type1 VDPV (iVDPV1) with 1.6% nucleotide divergence from the parent Sabin strain. E21 (19.4%), E14 (9%), E11 (9%), E16 (7.5%), and CVA2 (7.5%) were the five most frequently observed NPEV types in PID patients. Patients with combined immunodeficiency were at a higher risk for enterovirus infection as compared to antibody deficiency. The high susceptibility of PID patients to enterovirus infection emphasizes the need for enhanced surveillance of these patients until the use of OPV is stopped. The expansion of PID surveillance and integration with a national program will facilitate early detection and follow-up of iVDPV excretion to mitigate the risk for iVDPV spread.

A Retrospective Study of Clinical and Immunological Features of a Pediatric Population with Talaromyces marneffei Infection

BACKGROUND

Talaromyces marneffei (T. Marneffei) infection is considered as an indicator of immunosuppression in immunocompromised individuals, leading to multiple organ damage. Our study aimed to evaluate both the clinical characteristics and immunological features of pediatric patients infected with T. marneffei from our institute, providing novel insights into diagnosis and treatment for this life-threatening disease.

METHOD

Thirteen pediatric patients with T. marneffei infection were enrolled in Guangzhou Women and Children's Medical Center during 2012 to 2020. Clinical data and laboratory findings were collected and further analyzed. Pearson correlation coefficient was calculated to determine the relationship between serum immunoglobulins (Igs) levels and white blood cell count, or the absolute lymphocyte count.

RESULTS

Patients were diagnosed as having T. Marneffei infection mainly based on the results of fungal culture and Gram stain of specimens. The most common presentations were fever (69%), pneumonia (38%) and immunodeficiency (38%). The total levels of Igs (IgE, IgA, and IgM) were positively correlated with both white blood cell count and absolute lymphocyte count.

CONCLUSION

Serum Ig expression Pattern in patients diagnosed with T. marneffei infection might serve as an effective prognostic marker which would help with the development of early interventions for children with this fatal disease.

Infections in Inborn Errors of Immunity with Combined Immune Deficiency: A Review

Enhanced susceptibility to microbes, often resulting in severe, intractable and frequent infections due to usually innocuous organisms at uncommon sites, is the most striking feature in individuals with an inborn error of immunity. In this narrative review, based on the International Union of Immunological Societies' 2022 (IUIS 2022) Update on phenotypic classification of human inborn errors of immunity, the focus is on commonly encountered Combined Immunodeficiency Disorders (CIDs) with susceptibility to infections. Combined immune deficiency disorders are usually commensurate with survival beyond infancy unlike Severe Combined Immune Deficiency (SCID) and are often associated with clinical features of a syndromic nature. Defective humoral and cellular immune responses result in susceptibility to a broad range of microbial infections. Although disease onset is usually in early childhood, mild defects may present in late childhood or even in adulthood. A precise diagnosis is imperative not only for determining management strategies, but also for providing accurate genetic counseling, including prenatal diagnosis, and also in deciding empiric treatment of infections upfront before investigation reports are available.

The rs1883832 Polymorphism (CD40-1C>T) Affects the Intensity of IgA Responses after BNT162b2 Vaccination

The effectiveness of coronavirus disease 2019 (COVID-19) vaccination strategies is affected by several factors, including the genetic background of the host. In our study, we evaluated the contribution of the functional polymorphism rs1883832 affecting the Kozak sequence of the TNFSF5 gene (c.-1C>T), encoding CD40, to humoral immune responses after vaccination with the spike protein of SARS-CoV-2. The rs1883832 polymorphism was analyzed by PCR-RFLP in 476 individuals (male/female: 216/260, median age: 55.0 years, range: 20−105) of whom 342 received the BNT162b2 mRNA vaccine and 134 received the adenovirus-based vector vaccines (67 on ChAdOx1-nCoV-19 vaccine, 67 on Ad.26.COV2.S vaccine). The IgG and IgA responses were evaluated with chemiluminescent microparticle and ELISA assays on days 21, 42, and 90 after the first dose. The T allele of the rs1883832 polymorphism (allele frequency: 32.8%) was significantly associated with lower IgA levels and represented, as revealed by multivariable analysis, an independent risk factor for reduced anti-spike protein IgA levels on days 42 and 90 following BNT162b2 mRNA vaccination. Similar to serum anti-spike IgA levels, a trend of lower anti-spike IgA concentrations in saliva was found in individuals with the T allele of rs1883832. Finally, the intensity of IgA and IgG responses on day 42 significantly affected the prevalence of COVID-19 after vaccination. The rs1883832 polymorphism may be used as a molecular predictor of the intensity of anti-spike IgA responses after BNT162b2 mRNA vaccination.

Current and future treatment in primary Sjögren's syndrome - A still challenging development

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease characterized by sicca symptoms, systemic manifestations and constitutional symptoms substantially diminishing patient's quality of life. In this review, we summarize recent recommendations for management of pSS patients and current clinical studies in pSS addressing unmet medical needs. Expanding knowledge about disease pathogenesis and the introduction of validated outcome measures, such as capturing disease activity (ESSDAI) and patient-reported outcomes (ESSPRI) have shaped recent developments. In contrast, lack of evidence for current treatment options remarkably limits the management of pSS patients as reflected by the 2019 updated EULAR recommendations for management of Sjögren's syndrome. In this context, symptomatic treatment is usually appropriate for sicca symptoms, whereas systemic treatment is reserved for moderate to severe organ manifestations including care by a multidisciplinary team in centers of expertise. Most promising targets for new treatment modalities are based on immunopathological insights and include direct B cell targeting strategies, targeting co-stimulation by CD40/CD40L blocking, inhibition of key cytokine activity (BLyS/BAFF, type I interferon) and intracellular signaling pathways.

Somatic hypermutation defects in two adult hyper immunoglobulin M patients

Hyper immunoglobulin M (HIGM) syndrome is a rare disorder of the immune system with impaired antibody functions. The clinical picture of the patients varies according to the underlying genetic variation. In this study, we identified two novel variants in AID and UNG genes, which are associated with autosomal recessive type HIGM, by targeted next-generation sequencing (NGS) panel. A biallelic 11 base pair deletion (c.278_288delATGTGGCCGAC) in the coding sequence of activation-induced cytidine deaminase (AID) gene was identified in a 36-year-old patient. Biallelic two base pair insertion in exon 7 of uracil nucleoside glycosylase (UNG) gene (c.924_925insGG) was identified in a 40-year-old patient. Both variants were confirmed by Sanger sequencing. HIGM, like many of the other primary immunodeficiencies, is a rare and difficult-to-diagnose entity with heterogeneous clinical phenotypes. It should be suspected in patients with a history of early-onset recurrent respiratory infections, enlarged lymph nodes, and autoimmune disorders. There might be a delay in diagnosis until adulthood especially in subtle cases or if HIGM is not included in the differential diagnosis due lacking of awareness. In this regard, genetic testing with NGS-based diagnostic panels provide a rapid and reasonable tool for the molecular diagnosis of patients with immunodeficiencies and hence, decrease the time to diagnose and prevent infection-related complications associated with increased morbidity and mortality.

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.

X-linked hyper IgM syndrome with severe eosinophilia: a case report and review of the literature

Background

Hyper IgM syndromes (HIGMS) are a group of rare primary immunodeficiency disorders. There are limited reports about HIGMS combined with severe eosinophilia.

Case presentation

In this report, we described a 2-year-old boy with chronic cough and symptoms of hypoxia. Lung computed tomography (CT) scan showed that diffuse ground-glass changes and eosinophils in peripheral blood increased significantly. Subsequent tests revealed a notable decrease in serum IgG and IgA. The lymphocyte subgroup classification was basically normal. Pneumocystis jirovecii were detected from the bronchoalveolar lavage fluid (BALF) of the patient by metagenomic next-generation sequencing (mNGS). After treatments of caspofungin combined with sulfamethoxazole, intravenous immunoglobulin (IVIG) replacement and anti-inflammatory steroid, the clinical symptoms and pulmonary imaging noticeably improved. The absolute eosinophil count (AEC) also returned to normal range. X-linked hyper IgM syndrome was confirmed by gene test. Two months after the diagnosis, the patient underwent allogeneic stem cell transplantation (HSCT) and has recovered well.

Conclusions

Children with HIGMS are prone to opportunistic infections such as Pneumocystis jirovecii pneumonia (PJP). Diffuse interstitial lung disease and hypoglobulinemia in a young child predict the diagnosis of a primary immunodeficiency (PID). mNGS has obvious advantages for obtaining etiological diagnosis of children with PIDs. Severe eosinophilia is rarely reported in this kind of PIDs. Considering literature review and the corresponding reaction to steroid, we proposed that eosinophilia in HIGMS might be related to infections. Steroid therapy can quickly relieve eosinophilia but is easy to rebound if the reduction is too fast. Once the diagnosis of HIGMS is confirmed, the earlier the HSCT, the better the prognosis.

Autoimmunity in Primary Immunodeficiency Disorders: An Updated Review on Pathogenic and Clinical Implications

During the last years, studies investigating the intriguing association between immunodeficiency and autoimmunity led to the discovery of new monogenic disorders, the improvement in the knowledge of the pathogenesis of autoimmunity, and the introduction of targeted treatments. Autoimmunity is observed with particular frequency in patients with primary antibody deficiencies, such as common variable immunodeficiency (CVID) and selective IgA deficiency, but combined immunodeficiency disorders (CIDs) and disorders of innate immunity have also been associated with autoimmunity. Among CIDs, the highest incidence of autoimmunity is described in patients with autoimmune polyendocrine syndrome 1, LRBA, and CTLA-4 deficiency, and in patients with STAT-related disorders. The pathogenesis of autoimmunity in patients with immunodeficiency is far to be fully elucidated. However, altered germ center reactions, impaired central and peripheral lymphocyte negative selection, uncontrolled lymphocyte proliferation, ineffective cytoskeletal function, innate immune defects, and defective clearance of the infectious agents play an important role. In this paper, we review the main immunodeficiencies associated with autoimmunity, focusing on the pathogenic mechanisms responsible for autoimmunity in each condition and on the therapeutic strategies. Moreover, we provide a diagnostic algorithm for the diagnosis of PIDs in patients with autoimmunity.

Immune checkpoints and the multiple faces of B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

B-lymphocytes are crucial in the pathogenesis of systemic lupus erythematosus (SLE), including autoantibody production, antigen presentation, co-stimulation, and cytokine secretion. Co-stimulatory and co-inhibitory molecules control interactions between B and T cells during an inflammatory response, which is essential for an appropriate host protection and maintenance of self-tolerance. Here, we review recent findings about checkpoint molecules and SLE B cells including their potential therapeutic implications and experiences from clinical trials.

RECENT FINDINGS

Most prominent checkpoint molecules involved in pathologic B and T cell interaction in SLE are CD40/CD40L and inducible co-stimulator/ICOSL, both also intimately involved in the formation of germinal centers and ectopic lymphoid tissue. Dysregulations of inhibitory checkpoint molecules, like programmed death-1/programmed death-ligand 1 and B- and T-lymphocyte attenuator have been suggested to impair B cell functions in SLE recently.

SUMMARY

Accumulating evidence indicates that dampening immune responses by either blocking co-activating signals or enhancing co-inhibitory signals in different cell types is a promising approach to treat autoimmune diseases to better control active disease but may also allow resolution of chronic autoimmunity.

Human Germinal Center Reaction: Assessing T Follicular Helper-B Cells Interaction In Vitro

Antibody responses deeply rely on the interaction of antigen-primed B cells and CD4 helper T cells in the context of germinal center reactions, through signals provided by costimulatory molecules and cytokines. B-cell proliferation and differentiation in antibody-secreting plasma cells are processes that critically depend on the helper function of a specific CD4 T-cell subset, known as follicular helper T cells (Tfh). Here, we describe a method that mimics in vitro the cross talk between Tfh and B cells occurring in the germinal center. The procedure is based on setting up a coculture system with B cells and Tfh isolated from blood of healthy donors, or tonsils removed upon surgical intervention, in order to recapitulate in vitro the Tfh-dependent mechanisms leading to B cells' activation, proliferation, and differentiation.

Autoreactive T cells in pemphigus: perpetrator and target

Pemphigus vulgaris (PV) is an autoimmune blistering disease, in which autoantibodies against epidermal cadherins, such as desmoglein (Dsg)1 and Dsg3, lead to the development of blisters and erosions on the skin and mucous membranes. Autoreactive CD4+ T cells are essential for the induction and perpetuation of the disease by interaction with B cells producing autoantibodies. PV has a strong genetic association with certain human leucocyte antigen (HLA) alleles with HLA-DRB1*04:02 and LA-DQB1*05:03 being the most prevalent in patients. Recently, genome-wide association studies have provided a new approach to identify single nucleotide polymorphisms, alongside the known association with HLA alleles. Loss of tolerance against Dsgs and other autoantigens is a critical event in the pathogenesis of PV. Epitope spreading contributes to the progression of PV, leading to an extension of the Dsg-specific autoimmune response to other molecular epitopes of autoantigens, such as desmocollins or muscarinic receptors. Alterations in CD4+CD25+ FoxP3+ regulatory T cells are thought to contribute to the development of PV representing a suitable target for therapeutic interventions. Several CD4+ T-cell subsets and cytokines are involved in the pathogenesis of PV, while Th2 cells are the extensively studied population. Recently, other T cell subsets like T follicular helper cells and Th17 have gained attention as new potential players in PV pathogenesis. The involvement of local autoantibody production in the lesional skin of PV patients in tertiary lymphoid organs is currently discussed but not yet clarified. In this study, we reviewed the current knowledge about the development, characteristics and function of autoreactive T cells in pemphigus and present current new T cell-targeted therapeutic approaches.

Targeting co-stimulatory molecules in autoimmune disease

Therapeutic targeting of immune checkpoints has garnered significant attention in the area of cancer immunotherapy, in which efforts have focused in particular on cytotoxic T lymphocyte antigen 4 (CTLA4) and PD1, both of which are members of the CD28 family. In autoimmunity, these same pathways can be targeted to opposite effect: to curb the over-exuberant immune response. The CTLA4 checkpoint serves as an exemplar, whereby CTLA4 activity is blocked by antibodies in cancer immunotherapy and augmented by the provision of soluble CTLA4 in autoimmunity. Here, we review the targeting of co-stimulatory molecules in autoimmune diseases, focusing in particular on agents directed at members of the CD28 or tumour necrosis factor receptor families. We present the state of the art in co-stimulatory blockade approaches, including rational combinations of immune inhibitory agents, and discuss the future opportunities and challenges in this field.

T cell gene therapy to treat immunodeficiency

The application of therapeutic T cells for a number of conditions has been developed over the past few decades with notable successes including donor lymphocyte infusions, virus-specific T cells and more recently CAR-T cell therapy. Primary immunodeficiencies are monogenetic disorders leading to abnormal development or function of the immune system. Haematopoietic stem cell transplantation and, in specific candidate diseases, haematopoietic stem cell gene therapy has been the only definitive treatment option so far. However, autologous gene-modified T cell therapy may offer a potential cure in conditions primarily affecting the lymphoid compartment. In this review we will highlight several T cell gene addition or gene-editing approaches in different target diseases with a focus on what we have learnt from clinical experience and promising preclinical studies in primary immunodeficiencies. Functional T cells are required not only for normal immune responses to infection (affected in CD40 ligand deficiency), but also for immune regulation [disrupted in IPEX syndrome (immune dysregulation, polyendocrinopathy, enteropathy, X-Linked) due to dysfunctional FOXP3 and CTLA4 deficiency] or cytotoxicity [defective in X-lymphoproliferative disease and familial haemophagocytic lymphohistiocytosis (HLH) syndromes]. In all these candidate diseases, restoration of T cell function by gene therapy could be of great value.

CD40 Ligand Deficiency

CD40 ligand deficiency (CD40L), currently classified as an inborn error of immunity affecting cellular and humoral immunity, prevalently emerges in boys within the first two years of life. It manifests itself as a decrease in serum IgG, IgA and IgE, with normal or high IgM, defects in T cell proliferation, and decrease in soluble CD40L. These accompany sinopulmonary and/or gastrointestinal infections, and there may be infections caused by pyogenic bacteria, opportunistic infections, autoimmune diseases, and neoplasms. Mild and moderate cases of this deficiency may respond well to prophylactic antibiotic therapy or to human immunoglobulin replacement therapy, in addition to the early treatment of infections. Severe cases can be treated with hematopoietic stem cell transplantation, which allows the healing of such patients, rather than sequelae and a poor progression. Thus, its differential diagnosis with other inborn errors of immunity is essential, especially CD40 deficiency and variable common immunodeficiency; the reason why we have proposed the present literature review.

Primary Antibody Deficiencies

Primary antibody deficiencies (PADs) are the most common types of inherited primary immunodeficiency diseases (PIDs) presenting at any age, with a broad spectrum of clinical manifestations including susceptibility to infections, autoimmunity and cancer. Antibodies are produced by B cells, and consequently, genetic defects affecting B cell development, activation, differentiation or antibody secretion can all lead to PADs. Whole exome and whole genome sequencing approaches have helped identify genetic defects that are involved in the pathogenesis of PADs. Here, we summarize the clinical manifestations, causal genes, disease mechanisms and clinical treatments of different types of PADs.

In vivo Screen Identifies Zdhhc2 as a Critical Regulator of Germinal Center B Cell Differentiation

Germinal center (GC) B cell differentiation is critical for the production of affinity-matured pathogen-specific antibodies, the dysregulation of which may lead to humoral immunodeficiency or autoimmunity. The development of an in vivo screening system for factors regulating GC B cell differentiation has been a challenge. Here we describe a small-scale in vivo screening system with NP-specific B1-8^hi cells and a retroviral shRNA library targeting 78 candidate genes to search for B cell-intrinsic factors that specifically regulate GC B cell differentiation. Zdhhc2, a gene encoding palmitoyltransferase ZDHHC2 and highly expressed in GC B cells, is identified as a strong positive regulator of GC B cell differentiation. B1-8^hi cells transduced with Zdhhc2-shRNA are severely compromised in differentiating into GC B cells. A further analysis of in vitro differentiated B cells transduced with Zdhhc2-shRNA shows that Zdhhc2 is critical for the proliferation and the survival of B cells stimulated by CD40L, BAFF, and IL-21 and consequently impacts on their differentiation into GC B cells and post-GC B cells. These studies not only identify Zdhhc2 as a novel regulator of GC B cell differentiation but also represent a proof of concept of in vivo screen for regulators of GC B cell differentiation.

First-in-human clinical trial to assess pharmacokinetics, pharmacodynamics, safety, and tolerability of iscalimab, an anti-CD40 monoclonal antibody

Iscalimab is a fully human, CD40 pathway blocking, nondepleting monoclonal antibody being developed as an immunosuppressive agent. We describe a first-in-human, randomized, double-blind, placebo-controlled study investigating the safety, tolerability, pharmacokinetics, and pharmacodynamics of iscalimab in healthy subjects and rheumatoid arthritis patients. Healthy subjects (n = 56) received single doses of intravenous iscalimab (0.03, 0.1, 0.3, 1, or 3 mg/kg), or subcutaneous iscalimab (3 mg/kg), or placebo. Rheumatoid arthritis patients (n = 20) received single doses of intravenous iscalimab (10 or 30 mg/kg) or placebo. Iscalimab exhibited target-mediated drug disposition resulting in dose-dependent and nonlinear pharmacokinetics. Complete (≥90%) CD40 receptor occupancy on whole blood B cells was observed at plasma concentrations >0.3-0.4 µg/mL. In subjects receiving 3 mg/kg iscalimab, antibody responses to keyhole limpet hemocyanin were transiently suppressed. CD40 occupancy by iscalimab prevented ex vivo human rCD154-induced expression of CD69 on B cells in whole blood. All doses were generally safe and well tolerated, with no clinically relevant changes in any safety parameters, including no evidence of thromboembolic events. Iscalimab appears to be a promising blocker of the CD40-CD154 costimulatory pathway with potential use in transplantation and other autoimmune diseases.

The quantification of antibody elements and receptors subunit expression using qPCR: The design of VH, VL, CH, CL, FcR subunits primers for a more holistic view of the immune system

The expression levels of immunoglobulin elements and their receptors are important markers for health and disease. Within the immunoglobulin locus, the constant regions and the variable region families are associated with certain pathologies, yet a holistic view of the interaction between the expressions of the multiple genes remain to be fully characterized. There is thus an important need to quantify antibody elements, their receptors and the receptor subunits in blood (PBMC cDNA) for both screening and detailed studies of such associations. Leveraging on qPCR, we designed primers for all Vκ1-6, VH1-7, Vλ1-11, nine CH isotypes, Cκ, Cκ, Cλ1 &3, FcεRI α,β, and γ subunits, all three FcγR and their subunits, and FcαR. Validating this on a volunteer PBMC cDNA, we report a qPCR primer set repertoire that can quantify the relative expression of all the above genes to the GAPDH housekeeping gene, with implications and uses in both clinical monitoring and research.

Clinical Manifestations, Immunological Characteristics and Genetic Analysis of Patients with Hyper-Immunoglobulin M Syndrome in Iran

BACKGROUND

Hyper-immunoglobulin M (HIGM) syndrome is a rare heterogeneous group of primary immunodeficiency disorders characterized by low or absent serum levels of IgG and IgA along with normal or elevated serum levels of IgM.

METHODS

Clinical and immunological data were collected from the 75 patients' medical records diagnosed in Children's Medical Center affiliated to Tehran University Medical Sciences and other Universities of Medical Sciences in Iran. Among 75 selected patients, 48 patients (64%) were analyzed genetically using targeted and whole-exome sequencing.

RESULTS

The ratio of male to female was 2.9:1. The median age at the onset of the disease, time of diagnosis, and diagnostic delay were 10.5, 50, and 24 months, respectively. Pneumonia and lower respiratory tract infections (61.3%) were the most common complications. Responsible genes were identified in 35 patients (72.9%) out 48 genetically analyzed patients. Cluster of differentiation 40 ligand gene was the most mutated gene observed in 24 patients (68.5%) followed by activation-induced cytidine deaminase gene in 7 patients, lipopolysaccharide-responsive and beige-like anchor (1 patient), nuclear factor-kappa-B essential modulator (1 patient), phosphoinositide-3-kinase regulatory subunit 1 (1 patient), and nuclear factor kappa B subunit 1 (1 patient) genes. Nineteen (25.3%) patients died during the study period, and pneumonia was the major cause of death occurred in 6 (31.6%) patients.

CONCLUSION

Physicians in our country should carefully pay attention to respiratory tract infections and pneumonia, particularly in patients with a positive family history. Further investigations are required for detection of new genes and pathways resulting in HIGM phenotype.

Targeting the CD40-CD40L pathway in autoimmune diseases: Humoral immunity and beyond

CD40 is a TNF receptor superfamily member expressed on both immune and non-immune cells. Interactions between B cell-expressed CD40 and its binding partner, CD40L, predominantly expressed on activated CD4+ T cells, play a critical role in promoting germinal center formation and the production of class-switched antibodies. Non-hematopoietic cells expressing CD40 can also engage CD40L and trigger a pro-inflammatory response. This article will highlight what is known about the biology of the CD40-CD40L axis in humans and describe the potential contribution of CD40 signaling on both hematopoietic and non-hematopoietic cells to autoimmune disease pathogenesis. Additionally, novel therapeutic approaches to target this pathway, currently being evaluated in clinical trials, are discussed.

The hyper IgM syndromes: Epidemiology, pathogenesis, clinical manifestations, diagnosis and management

Hyper Immunoglobulin M syndrome (HIGM) is a rare primary immunodeficiency disorder characterized by low or absent levels of serum IgG, IgA, IgE and normal or increased levels of serum IgM. Various X-linked and autosomal recessive/dominant mutations have been reported as the underlying cause of the disease. Based on the underlying genetic defect, the affected patients present a variety of clinical manifestations including pulmonary and gastrointestinal complications, autoimmune disorders, hematologic abnormalities, lymphoproliferation and malignancies which could be controlled by multiple relevant therapeutic approaches. Herein, the epidemiology, pathogenesis, clinical manifestations, diagnosis, management, prognosis and treatment in patients with HIGM syndrome have been reviewed.

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.

Tumor Necrosis Factor Receptor Superfamily in T Cell Priming and Effector Function

The tumor necrosis factor receptor superfamily (TNFRSF) and their ligands mediate lymphoid tissue development and homeostasis in addition to key aspects of innate and adaptive immune responses. T cells of the adaptive immune system express a number of TNFRSF members that are used to receive signals at different instructive stages and produce several tumor necrosis factor superfamily (TNFSF) members as effector molecules. There is also one example of a TNFRSF member serving as a ligand for negative regulatory checkpoint receptors. In most cases, the ligands in afferent and efferent phases are membrane proteins and thus the interaction with TNFRSF members must take place in immunological synapses and other modes of cell-cell interaction. A particular feature of the TNFRSF-mediated signaling is the prominent use of linear ubiquitin chains as scaffolds for signaling complexes that activate nuclear factor κ-B and Fos/Jun transcriptional regulators. This review will focus on the signaling mechanisms triggered by TNFRSF members in their role as costimulators of early and late phases of T cell instruction and the delivery mechanism of TNFSF members through the immunological synapses of helper and cytotoxic effector cells.

Haematopoietic stem cell transplant for hyper-IgM syndrome due to CD40 defects: a single-centre experience

Hyper-IgM syndrome due to CD40 deficiency (HIGM3) is a rare disease with only a few reported cases of haematopoietic stem cell transplantation (HSCT). In retrospective study, we reviewed all patients with HIGM3 who underwent HSCT at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia, between 2008 and 2013. Six patients were identified. Three male and three female patients from three families. The median age of diagnosis was 13 months (range, 1-28 months). All lacked CD40 expression on B cells by flow cytometry. The median time from diagnosis to transplantation was 8.5 months (range, 1-17 months). For all patients, the donors were HLA-identical siblings, with the exception of one patient for whom the donor was a sibling with one antigen mismatch. The conditioning regimen was busulfan and cyclophosphamide in five patients and busulfan, cyclophosphamide and antithymocyte globulin in one patient. For GVHD prophylaxis, cyclosporine and methotrexate was used. All patients engrafted. The survival rate was 100%, with a median follow-up of 54 months (range, 30-116 months). One patient developed acute GVHD. All patients showed complete immune recovery with positive CD40 expression on B cells and discontinued IVIG replacement. Our study shows that HSCT is potentially effective at curing the disease.

Comprehensive review of autoantibodies in patients with hyper-IgM syndrome

Hyper-immunoglobulin M syndrome is an X-linked primary immunodeficiency disease caused by mutations in the CD40 ligand gene. The CD40 ligand has been recently highlighted as playing a key role in the pathogenesis of primary biliary cholangitis. In the present study, we assessed an extensive set of serum autoantibodies in a series of well-defined patients with hyper-immunoglobulin M syndrome. Serum, liver-related and liver-not-related autoantibodies IgG, IgM and IgA were tested by ELISA and standard indirect immunofluorescence in HEp-2 cells in 13 Tunisian patients (8 males and 5 females, aged 1-12 years) with hyper-immunoglobulin M syndrome during 1995-2012 and, as controls, 21 age- and gender-matched blood donors. The level of IgM antibody against MIT3 was significantly higher in patients than in controls (35.8 vs 10.7, P=0.002). Half of the hyperimmunoglobulin M syndrome patients were found to be anti-MIT3 IgM positive vs none of the controls (P<0.0001). Twenty-three percent of patients were found to be anti-sp100 antibody positive vs only 0.05% of controls. By immunofluorescence, 92.3% of patients were MIT3 IgM positive vs none of the controls. In conclusion, the IgM class of anti-MIT3 antibodies was shown to be present by both ELISA and immunofluorescence in most of the patients with hyper-immunoglobulin M syndrome. The presence of the hallmark of primary biliary cholangitis, a disease where the CD40 ligand is a key player, in an immunodeficiency disease caused by mutations in the CD40 ligand gene is very intriguing and opens new scenarios in understanding the immune pathogenesis of primary biliary cholangitis.

Ex Vivo Culture Assay to Measure Human Follicular Helper T (Tfh) Cell-Mediated Human B Cell Proliferation and Differentiation

Upon priming by antigens, B cells undergo activation, proliferation, and differentiation into antibody-secreting cells. During thymus-dependent (TD) antibody responses, the proliferation and differentiation of antigen-primed B cells essentially rely on the helper function from CD4⁺ T cells. Follicular helper T (Tfh) cells constitute a specialized Th subset that localizes in close proximity to B cells and supports B cell proliferation and differentiation through co-stimulatory receptors and cytokines. Impaired Tfh-mediated B cell proliferation and differentiation were observed in patients with immunodeficiency, while overactivation of this process may lead to dysregulated immune responses seen in autoimmune disorders. Here, we describe an ex vivo coculture assay using circulating Tfh cells and B cells isolated from human blood. This method can be used to examine the function of patients' B cells for proliferation, differentiation, and antibody secretion, mediated by the physiological help from Tfh cells.

Immunoglobulin and B-cell disturbances in patients with chronic idiopathic neutropenia

Chronic idiopathic neutropenia (CIN) is a granulocytic disorder associated with presence of activated, myelosuppressive T-lymphocytes. In the present study we have evaluated constituents of humoral immunity in CIN patients (n=48) compared to healthy controls (n=52). CIN patients displayed lower serum IgG levels due to a reduction in IgG1, IgG3, IgG4 but not IgG2, lower IgA and increased IgM levels compared to controls. The proportion of CD19⁺ cells did not differ between patients and controls; however the proportion of the naïve IgD⁺/CD27^- B-cells was increased and the proportion of class-switched memory IgD^-/CD27⁺ B-cells was decreased in the patients. The percentage of CD40⁺ B-cells did not differ between patients and controls and no aberrations in the CD40-meadiated signal transduction pathway or in CD40-gene polymorphisms were identified. These data provide further evidence that immune disturbances are associated with the pathophysiology of CIN and point out for the first time the implication of the B-cell system.

Hyper IgM Syndrome: a Report from the USIDNET Registry

PURPOSE

The United States Immunodeficiency Network (USIDNET) patient registry was used to characterize the presentation, genetics, phenotypes, and treatment of patients with Hyper IgM Syndrome (HIGM).

METHODS

The USIDNET Registry was queried for HIGM patient data collected from October 1992 to July 2015. Data fields included demographics, criteria for diagnosis, pedigree analysis, mutations, clinical features, treatment and transplant records, laboratory findings, and mortality.

RESULTS

Fifty-two physicians entered data from 145 patients of ages 2 months to 62 years (median 12 years); 131 were males. Using patients' age at last entry, data from 2072 patient years are included. Mutations were recorded for 85 subjects; 82 were in CD40LG. Eighteen subjects had non-X-linked HIGM. 40 % had a normal serum IgM and 15 %, normal IgA. Infections were reported for 91 %, with pulmonary, ear, and sinus infections being the most common. 42 % had Pneumocystis jirovecii pneumonia; 6 % had Cryptosporidium. 41 % had neutropenia. 78 % experienced non-infectious complications: chronic diarrhea (n = 22), aphthous ulcers (n = 28), and neoplasms (n = 8) including colon cancer, adrenal adenoma, liver adenocarcinoma, pancreatic carcinoid, acute myeloid leukemia, hepatoma, and, in a female with an autosomal dominant gain of function mutation in PIK3CD, an ovarian dysgerminoma. Thirteen patients had a hematopoietic marrow or stem cell transplant; three had solid organ transplants. Thirteen were known to have died (median age = 14 years).

CONCLUSIONS

Analysis of the USIDNET Registry provides data on the common clinical features of this rare syndrome, and in contrast with previously published data, demonstrates longer survival times and reduced gastrointestinal manifestations.

Increased serum IgM, immunodeficiency, and autoimmunity: A clinical series

BACKGROUND

Primary immunodeficiencies (PIDs) are generally characterized by recurrent infections; however they may be complicated by other clinical disorders such as allergy, autoimmunity, and lymphoproliferation. In particular, autoimmunity may be the first manifestation of the disease in patients with low serum immunoglobulins (Ig) levels. Here we describe a group of patients that share features of immunodeficiency and autoimmunity.

MATERIALS AND METHODS

All patients went through a complete T and B cell subset characterization and a B cell function analysis in the peripheral blood by flow-cytometry. B cell proliferation and plasma cell differentiation was measured, in vitro, after CpG stimulation for 7 days as previously described. Semi-quantitative PCR analysis for AID and UNG expression as well as serum levels of BAFF were carried out in order to better define the diagnosis.

RESULTS

Immunological and molecular analysis did not lead to the identification of known molecular defect typical of Hyper IgM syndrome. A comparative study of the peripheral blood B cell subsets between patients and healthy donors showed that in patients with autoimmune manifestations all circulating B cells expressed high amounts of surface IgM.

CONCLUSIONS

These results suggest that the increased IgM expression on circulating B cells, reflecting B cell activation, might identify a clinical condition characterized by hyper IgM serum levels of unknown molecular defects, associated with susceptibility to infections and autoimmunity.

Primary immunodeficiencies associated with eosinophilia

Background

Eosinophilia is not an uncommon clinical finding. However, diagnosis of its cause can be a dilemma once common culprits, namely infection, allergy and reactive causes are excluded. Primary immunodeficiency disorders (PID) are among known differentials of eosinophilia. However, the list of PIDs typically reported with eosinophilia is small and the literature lacks an inclusive list of PIDs which have been reported with eosinophilia. This motivated us to review the literature for all PIDs which have been described to have elevated eosinophils as this may contribute to an earlier diagnosis of PID and further the understanding of eosinophilia.

Methods

A retrospective PubMed, and Google Scholar search using the terms “eosinophilia” and “every individual PID” as classified by Expert Committee of the International Union of Immunological Societies with the limit of the English language was performed. Results were assessed to capture case(s) which reported eosinophilia in the context of PID conditions. Absolute eosinophil counts (AEC) were retrieved from manuscripts whenever reported.

Results

In addition to the typical PID conditions described with eosinophilia, we document that MHC class II deficiency, CD3γ deficiency, STAT1 deficiency (AD form), Kostmann disease, cyclic neutropenia, TCRα deficiency, Papillon-Lefevre syndrome, CD40 deficiency, CD40L deficiency, anhidrotic ectodermal dysplasia with immune deficiency, ataxia-telangiectasia, common variable immunodeficiency disorders (CVID), Blau syndrome, CARD9 deficiency, neonatal onset multisystem inflammatory disease or chronic infantile neurologic cutaneous and articular syndrome (NOMID/CINCA), chronic granulomatous disease, MALT1 deficiency and Roifman syndrome have been noted to have elevated eosinophils. Severe eosinophilia (>5.0 × 10⁹/L) was reported in Omenn syndrome, Wiskott Aldrich syndrome, ADA deficiency, autoimmune lymphoproliferative syndrome, immunodysregulation polyendocrinopathy enteropathy X-linked, STAT3 deficiency, DOCK8 deficiency, CD40 deficiency, MHC II deficiency, Kostmann disease, Papillon-Lefevre syndrome, and CVID.

Conclusions

This literature review shows that there is an extensive list of PIDs which have been reported with eosinophilia. This list helps clinicians to consider an extended differential diagnoses when tasked with exclusion of PID as a cause for eosinophilia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-016-0130-4) contains supplementary material, which is available to authorized users.

Autoimmunity in primary T-cell immunodeficiencies

Primary immunodeficiency diseases (PID) are a genetically heterogeneous group of more than 270 disorders that affect distinct components of both humoral and cellular arms of the immune system. Primary T cell immunodeficiencies affect subjects at the early age of life. In most cases, T-cell PIDs become apparent as combined T- and B-cell deficiencies. Patients with T-cell PID are prone to life-threatening infections. On the other hand, non-infectious complications such as lymphoproliferative diseases, cancers and autoimmunity seem to be associated with the primary T-cell immunodeficiencies. Autoimmune disorders of all kinds (organ specific or systemic ones) could be subjected to this class of PIDs; however, the most frequent autoimmune disorders are immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia (AIHA). In this review, we discuss the proposed mechanisms of autoimmunity and review the literature reported on autoimmune disorder in each type of primary T-cell immunodeficiencies.

Human T Follicular Helper Cells in Primary Immunodeficiency: Quality Just as Important as Quantity

T follicular helper (Tfh) cells are a subset of effector CD4(+) T cells specialised to induce Ab production by B cells. This review highlights some of the recent advances in the field of human Tfh cells that have come from the study of primary immunodeficiencies. In particular it is increasingly evident that the quality of the Tfh cells that are generated, is just as important as the quantity.

Unbalanced Immune System: Immunodeficiencies and Autoimmunity

Increased risk of developing autoimmune manifestations has been identified in different primary immunodeficiencies (PIDs). In such conditions, autoimmunity and immune deficiency represent intertwined phenomena that reflect inadequate immune function. Autoimmunity in PIDs may be caused by different mechanisms, including defects of tolerance to self-antigens and persistent stimulation as a result of the inability to eradicate antigens. This general immune dysregulation leads to compensatory and exaggerated chronic inflammatory responses that lead to tissue damage and autoimmunity. Each PID may be characterized by distinct, peculiar autoimmune manifestations. Moreover, different pathogenetic mechanisms may underlie autoimmunity in PID. In this review, the main autoimmune manifestations observed in different PID, including humoral immunodeficiencies, combined immunodeficiencies, and syndromes with immunodeficiencies, are summarized. When possible, the pathogenetic mechanism underlying autoimmunity in a specific PID has been explained.

Deleted in Breast Cancer 1 Suppresses B Cell Activation through RelB and Is Regulated by IKKα Phosphorylation

Alternative NF-κB signaling is crucial for B cell activation and Ig production, and it is mainly regulated by the inhibitor of κ B kinase (IKK) regulatory complex. Dysregulation of alternative NF-κB signaling in B cells could therefore lead to hyperactive B cells and Ig overproduction. In our previous, study we found that deleted in breast cancer 1 (DBC1) is a suppressor of the alternative NF-κB pathway to attenuate B cell activation. In this study, we report that loss of DBC1 results in spontaneous overproduction of Ig in mice after 10 mo of age. Using a double mutant genetic model, we confirm that DBC1 suppresses B cell activation through RelB inhibition. At the molecular level, we show that DBC1 interacts with alternative NF-κB members RelB and p52 through its leucine zipper domain. In addition, phosphorylation of DBC1 at its C terminus by IKKα facilitates its interaction with RelB and IKKα, indicating that DBC1-mediated suppression of alternative NF-κB is regulated by IKKα. Our results define the molecular mechanism of DBC1 inhibition of alternative NF-κB activation in suppressing B cell activation.

Pathophysiology of T follicular helper cells in humans and mice

Follicular helper T cells (TFH cells) compose a heterogeneous subset of CD4(+) T cells that induce the differentiation of B cells into plasma cells and memory cells. They are found within and in proximity to germinal centers in secondary lymphoid organs, and their memory compartment also circulates in the blood. Our knowledge on the biology of TFH cells has increased significantly during the past decade, largely as a result of mouse studies. However, recent studies on human TFH cells isolated from lymphoid organ and blood samples and recent observations on the developmental mechanism of human TFH cells have revealed both similarities and differences between human and mouse TFH cells. Here we present the similarities and differences between mouse and human lymphoid organ-resident TFH cells and discuss the role of TFH cells in response to vaccines and in disease pathogenesis.

Persistent Polyclonal B Cell Lymphocytosis B Cells Can Be Activated through CD40-CD154 Interaction

Persistent polyclonal B cell lymphocytosis (PPBL) is a rare disorder, diagnosed primarily in adult female smokers and characterized by an expansion of CD19⁺CD27⁺IgM⁺ memory B cells, by the presence of binucleated lymphocytes, and by a moderate elevation of serum IgM. The clinical course is usually benign, but it is not known whether or not PPBL might be part of a process leading to the emergence of a malignant proliferative disorder. In this study we sought to investigate the functional response of B cells from patients with PPBL by use of an optimal memory B cell culture model based on the CD40-CD154 interaction. We found that the proliferation of PPBL B cells was almost as important as that of B cells from normal controls, resulting in high immunoglobulin secretion with in vitro isotypic switching. We conclude that the CD40-CD154 activation pathway is functional in the memory B cell population of PPBL patients, suggesting that the disorder may be due to either a dysfunction of other cells in the microenvironment or a possible defect in another B cell activation pathway.

Immune activation and a 9-year ongoing complete remission following CD40 antibody therapy and metastasectomy in a patient with metastatic melanoma

Direct immune activation via agonistic mAbs is a potentially complementary approach to therapeutic blockade of inhibitory immune receptors in cancer. Here, we provide genetic analysis of the immunologic consequences associated with the use of an agonistic CD40 mAb in a patient with metastatic melanoma who responded, underwent a single metastasectomy, and then achieved a complete remission ongoing for more than 9 years after starting therapy. Tumor microenvironment after immunotherapy was associated with proinflammatory modulations and emergence of a de novo T-cell repertoire as detected by next-generation sequencing of T-cell receptors (TCR) in the tumor and blood. The de novo T-cell repertoire identified in the posttreatment metastasectomy sample was also present-and in some cases expanded-in the circulation years after completion of therapy. Comprehensive study of this "exceptional responder" highlights the emerging potential of direct immune agonists in the next wave of cancer immunotherapies and a potential role for TCR deep sequencing in cancer immune assessment.

Prevention of infections during primary immunodeficiency

Because infectious diseases are a major source of morbidity and mortality in the majority of patients with primary immunodeficiencies (PIDs), the application of a prophylactic regimen is often necessary. However, because of the variety of PIDs and pathogens involved, and because evidence is scarce, practices are heterogeneous. To homogenize practices among centers, the French National Reference Center for PIDs aimed at elaborating recommendations for anti-infectious prophylaxis for the most common PIDs. We performed a literature review of infectious complications and prophylactic regimens associated with the most frequent PIDs. Then, a working group including different specialists systematically debated about chemoprophylaxis, immunotherapy, immunization, and recommendations for patients. Grading of prophylaxis was done using strength of recommendations (decreasing from A to D) and evidence level (decreasing from I to III). These might help infectious diseases specialists in the management of PIDs and improving the outcome of patients with PIDs.

Late stages of hematopoiesis and B cell lymphopoiesis are regulated by α-synuclein, a key player in Parkinson's disease

α-Synuclein plays a crucial role in Parkinson's disease and dementias defined as synucleinopathies. α-Synuclein is expressed in hematopoietic and immune cells, but its functions in hematopoiesis and immune responses are unknown. We utilized α-synuclein(-/-) (KO) mice to investigate its role in hematopoiesis and B cell lymphopoiesis. We demonstrated hematologic abnormalities including mild anemia, smaller platelets, lymphopenia but relatively normal early hematopoiesis in KO mice compared to wild-type (WT) as measured in hematopoietic stem cells and progenitors of the different cell lineages. However, the absolute number of B220(+)IgM(+) B cells in bone marrow was reduced by 4-fold in KO mice (WT: 104±23×10(5) vs. KO: 27±5×10(5)). B cells were also reduced in KO spleens associated with effacement of splenic and lymph node architecture. KO mice showed reduced total serum IgG but no abnormality in serum IgM was noted. When KO mice were challenged with a T cell-dependent antigen, production of antigen specific IgG1 and IgG2b was abolished, but antigen specific IgM was not different from WT mice. Our study shows hematologic abnormalities including anemia and smaller platelets, reduced B cell lymphopoiesis and defects in IgG production in the absence of α-synuclein. This is the first report to show an important role of α-synuclein late in hematopoiesis, B cell lymphopoiesis and adaptive immune response.

X-linked hyper IgM syndrome: clinical, immunological and molecular features in patients from India

BACKGROUND

X-linked hyper-IgM (XHIM) is a primary immunodeficiency disorder characterized by recurrent infections, low serum IgG and IgA and normal or elevated IgM. It results from mutations in the CD40 ligand (CD40L) gene. Confirmation of diagnosis with identification of underlying molecular defect is important for the initiation of appropriate therapeutic interventions, including immunoglobulin replacement, antibiotics and bone marrow transplantation.

METHODS

To investigate the molecular basis of XHIM, we evaluated 7 patients with suspected XHIM and abnormal CD40L expression on activated CD4(+) T lymphocytes. The entire coding region and intronic splice sites of the CD40L gene were sequenced from the genomic DNA of the patients.

RESULTS

7 mutations; 3 nonsense (c.172delA, c.A229T, c.C478T), 1 missense (c.A506G) and 3 splice sites [c.346+2(T→C), c.289-1(G→C), c.346+1(G→T)] were identified, out of which 5 were novel.

CONCLUSION

A wide heterogeneity in the nature of mutations has been observed in Indian XHIM patients in the present study. Identification of mutations in this rare disorder will help in genetic diagnosis in affected families which could be further useful in prenatal diagnosis.

B-type suppression: a role played by "regulatory B cells" or "regulatory plasma cells"?

B-cell depletion can improve disease in some patients with rheumatoid arthritis or multiple sclerosis, indicating the pathogenic contribution of B cells to autoimmunity. However, studies in mice have demonstrated that B cells have immunosuppressive functions as well, with IL-10 being a critical mediator of B-cell-mediated suppression. IL-10-secreting B cells have been shown to promote disease remission in some mouse models of autoimmune disorders. Human B cells also produce IL-10, and evidence is accumulating that human IL-10-producing B cells might inhibit immunity. There is considerable interest in identifying the phenotype of B cells providing IL-10 in a suppressive manner, which would facilitate the analysis of the molecular mechanisms controlling this B-cell property. Here, we review current knowledge on the B-cell subpopulations found to provide suppressive functions in mice, considering both the pathological context in which they were identified and the signals that control their induction. We discuss the phenotype of B cells that have IL-10-dependent regulatory activities in mice, which leads us to propose that antibody-secreting cells are, in some cases at least, the major source of B-cell-derived regulatory IL-10 in vivo. Anti-inflammatory cytokine production by antibody-secreting cells offers a novel mechanism for the coordination of innate and humoral immune responses.