Clinical consequences of defects in B-cell development

Effects of porcine epidemic diarrhea virus infection on CD21+ B cells activation

Porcine epidemic diarrhea virus (PEDV) is a devastating pathogen of acute- gastrointestinal infectious diseases, which can cause vomiting, diarrhea, dehydration and high morbidity and mortality among neonatal piglets. Humoral immunity plays a vital role in the host anti-PEDV infection process, but the mechanism of PEDV-induced B-cell immune response remains unknown. In this study, the effects of PEDV infection on CD21+ B cell activation were systematically analyzed through animal experiments. Enzyme-linked immunosorbent assays (ELISA) revealed that low levels of serum-specific IgA, IgM, or IgG were detected in piglets after PEDV infection, respectively. Serum interleukin (IL)-6 levels increased significantly at 4 d after infection, and the levels of IL-4, B-cell activating factor (BAFF), interferon (IFN)-γ, transforming growth factor (TGF)-β and IL-10 decreased at 7 d after infection. Fluorescence-activated cell sorting (FACS) showed that expression levels of CD21, MHC Ⅱ, CD40, and CD38 on B cell surfaces were significantly higher. In contrast, the proportions of CD21+IgM+ B cells were decreased in peripheral blood mononuclear cells (PBMCs) from the infected piglets. No differences were found in the percentage of CD21+CD80+ and CD21+CD27+ B cells in PBMCs from the infected piglets. In addition, the number of CD21+B cells in PBMCs stimulated with PEDV in vitro was significantly lower. No significant change in the mRNA expression of BCR molecules was found while the expression levels of paired immunoglobulin-like receptor B (PIR-B), B cell adaptor molecule of 32 kDa (Bam32) and BAFF were decreased. In conclusion, our research demonstrates that virulent strains of PEDV profoundly impact B cell activation, leading to alterations in phenotypic expression and BCR signaling molecules. Furthermore, this dysregulation results in compromised specific antibody secretion and perturbed cytokine production, highlighting the intricate immunological dysfunctions induced by PEDV infection.

Normalized circulating Tfh and Th17 associates with improvement in myasthenia gravis treated with ofatumumab

Objective

To assess the effect of B cell depletion therapy (BCDT) on circulating T follicular helper (cTfh) and circulating T helper 17 (cTh17) cells and its relation to clinical improvement in patients with myasthenia gravis (MG).

Methods

28 anti-AchR positive MG patients treated with ofatumumab and 28 healthy controls (HCs) were included. Frequencies of cTfh and cTh17 cells were monitored by flow cytometry at baseline and 4, and 12 weeks after the initial dose ofatumumab. Serum cytokines associated with cTfh and cTh17, including IL-6, IL-21, and IL-17, were also analyzed.

Results

The frequency of cTfh and cTh17 significantly increased in MG patients compared with HCs. Additionally, elevated levels of both T-cell subsets correlated with MG severity. During the follow-up, cTfh and cTh17 return to normal after BCDT. Furthermore, the decrease in cTfh and cTh17 was associated with MG scores improvement over time. Notably, cTfh- and cTh17-related cytokines, including IL-6, IL-21, and IL-17, exhibited a marked decrease following ofatumumab therapy.

Conclusions

Abnormal expansion of cTfh and cTh17 cells may be key features in the immunopathology of MG. Their levels returned to normal after BCDT, which was closely correlated with clinical amelioration. This result suggests that these two T-cell subsets may be targets for BCDT treatment of MG.

Bone Marrow Changes in Septic Shock: A Comprehensive Review

Septic shock is a life-threatening condition characterized by systemic inflammation resulting from a severe infection. Although the primary focus of sepsis research has traditionally been on the dysfunctional immune response, recent studies have highlighted the important role of bone marrow in the pathophysiology of septic shock. The bone marrow, traditionally regarded as the hematopoietic organ responsible for blood cell production, undergoes significant changes during sepsis, contributing to the overall immune dysregulation observed in this condition. This comprehensive review aims to provide a detailed overview of the bone marrow changes associated with septic shock. It explores the alterations in the bone marrow microenvironment, hematopoietic progenitor cells, and the subsequent effects on leukocyte production and function. Key cellular and molecular mechanisms involved in bone marrow dysfunction during septic shock are discussed, including the dysregulation of cytokines, chemokines, growth factors, and signaling pathways. Furthermore, this review highlights the clinical implications of bone marrow changes in septic shock. It emphasizes the impact of altered hematopoiesis on immune cell populations, such as neutrophils, monocytes, and lymphocytes, and their role in the progression and outcome of sepsis. The potential prognostic value of bone marrow parameters and the therapeutic implications of targeting bone marrow dysfunction are also addressed. The review summarizes relevant preclinical and clinical studies to comprehensively understand the current knowledge of bone marrow changes in septic shock. The limitations and challenges of studying bone marrow in the context of sepsis are acknowledged, and future directions for research are proposed.

Membranous nephropathy: Mechanistic insights and therapeutic perspectives

Membranous nephropathy (MN) is one of the most common causes of non-diabetic nephrotic syndrome in adults. About 80% of cases are renal limited (primary MN) and 20% are associated with other systemic diseases or exposures (secondary MN). Autoimmune reaction is the main pathogenic factor of MN, and the discovery of autoantigens including the phospholipase A₂ receptor and thrombospondin type-1 domain-containing protein 7A has led to new insights into the pathogenesis, they can induce humoral immune responses led by IgG₄ makes them suitable for the diagnosis and monitoring of MN. In addition, complement activation, genetic susceptibility genes and environmental pollution are also involved in MN immune response. In clinical practice, due to the spontaneous remission of MN, the combination of supportive therapy and pharmacological treatment is widely used. Immunosuppressive drugs are the cornerstone of MN treatment, and the dangers and benefits of this approach vary from person to person. In summary, this review provides a more comprehensive review of the immune pathogenesis, interventions and unresolved issues of MN in the hope of providing some new ideas for clinical and scientific researchers in the treatment of MN.

Overview of human B-cell development and antibody deficiencies

B cells are a key component of the humoral (antibody-mediated) immune response which is responsible for defense against a variety of pathogens. Here we provide an overview of the current understanding of B cell development and function and briefly describe inborn errors of immunity associated with B cell development defects which can manifest as immune deficiency, malignancy, autoimmunity, or allergy. The knowledge and application of B cell biology are essential for laboratory evaluation and clinical assessment of these B cell disorders.

Transcriptomic analysis of B cells suggests that CD70 and LY9 may be novel features in patients with systemic lupus erythematosus

Dysfunction of B-cell subsets is critical in the development of systemic lupus erythematosus (SLE). There is a great diversity of B-lineage cells, and their features and functions in SLE need to be clarified. In this study, we analyzed single-cell RNA sequencing (scRNA-seq) data from peripheral blood mononuclear cells (PBMCs) and bulk transcriptomic data of isolated B-cell subsets from patients with SLE and healthy controls (HCs). We preformed scRNA-seq analysis focused on the diversity of B-cell subsets and identified a subset of antigen-presenting B cells in SLE patients that highly expressed ITGAX. A list of marker genes of each B-cell subset in patients with SLE was also identified. Comparison of bulk transcriptomic data of isolated B-cell subpopulations between SLE patients and HCs revealed the upregulated differentially expressed genes (DEGs) for each B-cell subpopulation in SLE. Common genes identified using these two methods were considered to be upregulated marker genes of B cells in SLE. The scRNA-seq data of SLE patients and HCs revealed that CD70 and LY9 were overexpressed in B cells vs. other cell types from SLE patients, and this pattern was validated by RT‒qPCR. Because CD70 is the cellular ligand of CD27, previous studies on CD70 have focused mainly on T cells from SLE patients. LY9 appears to have different functions in mice and humans: its expression is decreased in lupus-prone mice but is increased in T cells and some B-cell subpopulations in SLE patients. Here, we describe the overexpression of two costimulatory molecules, CD70 and LY9, which may be a novel feature of B cells in SLE patients.

Update on the Application of Monoclonal Antibody Therapy in Primary Membranous Nephropathy

When first introduced, rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, brought about an alternative therapeutic paradigm for primary membranous nephropathy (PMN). Rituximab was shown to be effective and safe in PMN patients with kidney dysfunction, with. patients receiving second-line rituximab therapy achieving remission as effectively as those patients who had not previously received immunotherapy. No safety issues were reported. The B cell-driven protocol seems to be as efficient as the 375 mg/m² × 4 regimen or 1 g × 2 regimen in achieving B cell depletion and remission, but patients with high M-type phospholipase A2 receptor (PLA2R) antibody levels may benefit from a higher dose of rituximab. While rituximab added another therapeutic option to the treatment regimen, it does have limitations as 20 to 40% of patients do not respond. Not all patients respond to RTX therapy for lymphoproliferative disorders either, therefore further novel anti-CD20 monoclonal antibodies have been developed and these may provide alternative therapeutic options for PMN. Ofatumumab, a fully human monoclonal antibody, specifically recognizes an epitope encompassing both the small and large extracellular loops of the CD20 molecule, resulting in increased complement-dependent cytotoxic activity. Ocrelizumab binds an alternative but overlapping epitope region to rituximab and displays enhanced antibody-dependent cellular cytotoxic (ADCC) activities. Obinutuzumab is designed to have a modified elbow-hinge amino acid sequence, leading to increased direct cell death induction and ADCC activities. In PMN clinical studies, ocrelizumab and obinutuzumab showed promising results, while ofatumumab displayed mixed results. However, there is a lack of randomized controlled trials with large samples, especially direct head-to-head comparisons. Alternative molecular mechanisms have been suggested in this context to explore novel therapeutic strategies. B cell activator-targeted, plasma cell-targeted and complement-directed treatments may lead to novel therapy paradigms for PMN. Exploratory strategies for the use of drugs with different mechanisms, such as a combination of rituximab and cyclophosphamide and a steroid, a combination of rituximab and a calcineurin inhibitor, may provide more rapid and efficient remission, but the combination of standard immunosuppression with rituximab could increase infection risk.

Clinical Outcome of Coronavirus Disease 2019 in Patients with Primary Antibody Deficiencies

In 2019, the novel coronavirus, SARS-CoV-2, caused a worldwide pandemic, affecting more than 630 million individuals and causing 6.5 million deaths. In the general population, poorer outcomes have been associated with older age, chronic lung and cardiovascular diseases, and lymphopenia, highlighting the important role of cellular immunity in the immune response against SARS-CoV-2. Moreover, SARS-CoV-2 variants may have a significant impact on disease severity. There is a significant overlap with complications commonly found in inborn errors of immunity (IEI), such as primary antibody deficiencies. The results of various studies have provided ambiguous findings. Several studies identified risk factors in the general population with a minor impact on SARS-CoV-2 infection. However, other studies have found a significant contribution of underlying immunodeficiency and immune-system dysregulation to the disease course. This ambiguity probably reflects the demographic differences and viral evolution. Impaired antibody production was associated with prolonged viral shedding, suggesting a critical role of humoral immunity in controlling SARS-CoV-2 infection. This may explain the poorer outcomes in primary antibody deficiencies compared to other IEIs. Understanding coronavirus disease 2019 (COVID-19) pathogenesis and identifying risk factors may help us identify patients at high risk of severe COVID-19 for whom preventive measures should be introduced.

The emerging scenario of immunotherapy for T-cell Acute Lymphoblastic Leukemia: advances, challenges and future perspectives

T-cell acute lymphoblastic leukemia (T-ALL) is a challenging pediatric and adult haematologic disease still associated with an unsatisfactory cure rate. Unlike B-ALL, the availability of novel therapeutic options to definitively improve the life expectancy for relapsed/resistant patients is poor. Indeed, the shared expression of surface targets among normal and neoplastic T-cells still limits the efficacy and may induce fratricide effects, hampering the use of innovative immunotherapeutic strategies. However, novel monoclonal antibodies, bispecific T-cell engagers (BTCEs), and chimeric antigen receptors (CAR) T-cells recently showed encouraging results and some of them are in an advanced stage of pre-clinical development or are currently under investigation in clinical trials. Here, we review this exciting scenario focusing on most relevant advances, challenges, and perspectives of the emerging landscape of immunotherapy of T-cell malignancies.

The third inactivated vaccine booster dramatically enhanced SARS-CoV-2 antibody responses and did not influence the profile of prothrombotic antibody

The purpose of this study is to investigate the production of both severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific antibodies and autoantibodies in serum following the third booster vaccination of the inactivated COVID-19 vaccine, and to study the effect of B cell subsets with CD27 and CD38 phenotypes in peripheral blood on antibody production. Routine blood indexes, SARS-CoV-2 antibodies, platelet factor 4 and seven antiphospholipid antibodies were detected both before and 2 months after vaccination in the medical staff of the Zhongnan Hospital of Wuhan University. Peripheral blood B cell subtypes were detected before vaccination. Following immunization, the positive rate of anti-N-S1 immunoglobulin (IgG) had increased from 24.8% to 91.3% and the average antibody concentration had increased by 11 times. The positive rate of neutralizing antibody had increased from 24.8% to 91.3%, the average antibody concentration had increased by 12 times, and the primary increased anti-S1 IgG subtype was that of IgG1. Peripheral blood CD27 + CD38+ B cells were positively correlated with antibody levels after vaccination and were a predictor of the antibody response. In addition, although some indicators showed slight absolute changes, the blood parameters and antiphospholipid antibodies of most volunteers were normal both before and after COVID-19 inactivated vaccine inoculation, and there was no statistical difference in abnormal rates either before or after inoculation. Antibodies in vivo were increased after vaccination with the inactivated vaccine, and IgG1 was the main subtype involved in response to the vaccine. Vaccination with the inactivated COVID-19 vaccine did not appear to affect thrombus-related autoantibodies.

The rapid inhibition of B-cell activation markers by belimumab was associated with disease control in systemic lupus erythematosus patients

Objective: To examine the kinetics of B cell subsets and activation markers in the early stage of belimumab treatment and their correction with treatment response. Methods: We enrolled 27 systemic lupus erythematosus (SLE) patients receiving 6 months belimumab treatment. Flow cytometry was used to test their B cell subsets and activation markers (including CD40, CD80, CD95, CD21^low, CD22, p-SYK and p-AKT). Results: During belimumab treatment, SLEDAI-2K declined, the proportions of CD19⁺ B cells and naïve B cells decreased, whereas the switched memory B cells and non-switched B cells increased. The larger variations of the B cell subsets and the activation markers were in the first 1 month than the other later time frames. The ratio of p-SYK/p-AKT on non-switched B cell at 1 month was associated with the SLEDAI-2K decline rate in the 6 months of belimumab treatment. Conclusion: B cell hyperactivity was rapidly inhibited in the early stage of belimumab treatment, and the ratio of p-SYK/p-AKT may predict SLEDAI-2K decline. Clinical Trial Registration: https://www.clinicaltrials.gov/ct2/show/NCT04893161?term=NCT04893161&draw=2&rank=1; identifier: NCT04893161.

Comparison of the deep immune profiling of B cell subsets between healthy adults and Sjögren's syndrome

OBJECTIVES

Detailed analysis targeting B cell subgroups was considered crucial in monitoring autoimmune diseases and treatment responses. Thus, precisely describing the phenotypes of B cell differentiation and their variation in primary Sjögren's syndrome (pSS) is particularly needed.

METHODS

To characterize the proportions and absolute counts of B cell subsets, peripheral blood from 114 healthy adults of China (age range: 19-73 years) and 55 patients with pSS were performed by flow cytometry and CD19, CD20, CD24, CD27, CD38 and IgD were used as surface markers to identify B cell mature process. Age- and gender-stratified analyses were then carried out to improve the interpretation of B cell subsets.

RESULTS

The assessments from healthy adults showed that the proportion of naive B cells presented a significant increase with age. A reversal trend was noted that the percentage of B10 decreased markedly with age. In addition, analysis based on gender showed that the relative percentage and number of naive B cells were higher in females than in males whereas the proportions of switched memory B cells and B10 cells were decreased in female. Patients with pSS exhibited a significant expansion in naïve B cells and unswitched memory B cells, accompanied with decreased switched memory B cells and B10 cells, which were identified to be associated with autoantibody production.

CONCLUSIONS

Our study presented a reliable analysis by flow cytometry to cover the principal B cell subtypes. These different stages of B lymphocytes may have implications for evaluating the activation of pSS and other autoimmune diseases and treatment efficacy.KEY MESSAGESB cell subsets play a pivotal role in the pathogenesis of primary Sjögren's syndrome (pSS) and other autoimmune diseases. A practical and accurate flow cytometry method to profile B cell phenotypes in peripheral blood of healthy adults is especially essential.Additionally, we presented reliable reference ranges for B cell subsets in regards to the local population. Age- and gender-related analyses are available to better understand their influence in immune status and treatment outcome.The distribution of B-cell subsets is found substantially altered in patients with pSS, bringing novel avenues for pSS research in the future.

Nanocarriers as a Delivery Platform for Anticancer Treatment: Biological Limits and Perspectives in B-Cell Malignancies

Nanoparticle-based therapies have been proposed in oncology research using various delivery methods to increase selectivity toward tumor tissues. Enhanced drug delivery through nanoparticle-based therapies could improve anti-tumor efficacy and also prevent drug resistance. However, there are still problems to overcome, such as the main biological interactions of nanocarriers. Among the various nanostructures for drug delivery, drug delivery based on polymeric nanoparticles has numerous advantages for controlling the release of biological factors, such as the ability to add a selective targeting mechanism, controlled release, protection of administered drugs, and prolonging the circulation time in the body. In addition, the functionalization of nanoparticles helps to achieve the best possible outcome. One of the most promising applications for nanoparticle-based drug delivery is in the field of onco-hematology, where there are many already approved targeted therapies, such as immunotherapies with monoclonal antibodies targeting specific tumor-associated antigens; however, several patients have experienced relapsed or refractory disease. This review describes the major nanocarriers proposed as new treatments for hematologic cancer, describing the main biological interactions of these nanocarriers and the related limitations of their use as drug delivery strategies.

SARS-CoV-2-Induced Immunosuppression: A Molecular Mimicry Syndrome

Background  Contrary to immunological expectations, decay of adaptive responses against severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) characterizes recovered patients compared with patients who had a severe disease course or died following SARS-CoV-2 infection. This raises the question of the causes of the virus-induced immune immunosuppression. Searching for molecular link(s) between SARS-CoV-2 immunization and the decay of the adaptive immune responses, SARS-CoV-2 proteome was analyzed for molecular mimicry with human proteins related to immunodeficiency. The aim was to verify the possibility of cross-reactions capable of destroying the adaptive immune response triggered by SARS-CoV-2.

Materials and Methods  Human immunodeficiency–related proteins were collected from UniProt database and analyzed for sharing of minimal immune determinants with the SARS-CoV-2 proteome.

Results  Molecular mimicry and consequent potential cross-reactivity exist between SARS-CoV-2 proteome and human immunoregulatory proteins such as nuclear factor kappa B (NFKB), and variable diversity joining V(D)J recombination-activating gene (RAG).

Conclusion  The data (1) support molecular mimicry and the associated potential cross-reactivity as a mechanism that can underlie self-reactivity against proteins involved in B- and T-cells activation/development, and (2) suggest that the extent of the immunosuppression is dictated by the extent of the immune responses themselves. The higher the titer of the immune responses triggered by SARS-CoV-2 immunization, the more severe can be the cross-reactions against the human immunodeficiency–related proteins, the more severe the immunosuppression. Hence, SARS-CoV-2-induced immunosuppression can be defined as a molecular mimicry syndrome. Clinically, the data imply that booster doses of SARS-CoV-2 vaccines may have opposite results to those expected.

The Role of Genome Sequencing in Neonatal Intensive Care Units

Genetic diseases disrupt the functionality of an infant's genome during fetal-neonatal adaptation and represent a leading cause of neonatal and infant mortality in the United States. Due to disease acuity, gene locus and allelic heterogeneity, and overlapping and diverse clinical phenotypes, diagnostic genome sequencing in neonatal intensive care units has required the development of methods to shorten turnaround times and improve genomic interpretation. From 2012 to 2021, 31 clinical studies documented the diagnostic and clinical utility of first-tier rapid or ultrarapid whole-genome sequencing through cost-effective identification of pathogenic genomic variants that change medical management, suggest new therapeutic strategies, and refine prognoses. Genomic diagnosis also permits prediction of reproductive recurrence risk for parents and surviving probands. Using implementation science and quality improvement, deployment of a genomic learning healthcare system will contribute to a reduction of neonatal and infant mortality through the integration of genome sequencing into best-practice neonatal intensive care.

Regeneration of immunocompetent B lymphopoiesis from pluripotent stem cells guided by transcription factors

Regeneration of functional B lymphopoiesis from pluripotent stem cells (PSCs) is challenging, and reliable methods have not been developed. Here, we unveiled the guiding role of three essential factors, Lhx2, Hoxa9, and Runx1, the simultaneous expression of which preferentially drives B lineage fate commitment and in vivo B lymphopoiesis using PSCs as a cell source. In the presence of Lhx2, Hoxa9, and Runx1 expression, PSC-derived induced hematopoietic progenitors (iHPCs) immediately gave rise to pro/pre-B cells in recipient bone marrow, which were able to further differentiate into entire B cell lineages, including innate B-1a, B-1b, and marginal zone B cells, as well as adaptive follicular B cells. In particular, the regenerative B cells produced adaptive humoral immune responses, sustained antigen-specific antibody production, and formed immune memory in response to antigen challenges. The regenerative B cells showed natural B cell development patterns of immunoglobulin chain switching and hypermutation via cross-talk with host T follicular helper cells, which eventually formed T cell-dependent humoral responses. This study exhibits de novo evidence that B lymphopoiesis can be regenerated from PSCs via an HSC-independent approach, which provides insights into treating B cell-related deficiencies using PSCs as an unlimited cell resource.

The emerging role non-coding RNAs in B cell-related disorders

Long non-coding RNAs and microRNAs have recently attained much attention regarding their role in the development of B cell lineage as well as participation in the lymphomagenesis. These transcripts have a highly cell type specific signature which endows them the potential to be used as biomarkers for clinical situations. Aberrant expression of several non-coding RNAs has been linked with B cell malignancies and immune related disorders such as rheumatoid arthritis, systemic lupus erythematous, asthma and graft-versus-host disease. Moreover, these transcripts can alter response of immune system to infectious conditions. miR-7, miR-16-1, miR-15a, miR-150, miR-146a, miR-155, miR-212 and miR-132 are among microRNAs whose role in the development of B cell-associated disorders has been investigated. Similarly, SNHG14, MALAT1, CRNDE, AL133346.1, NEAT1, SMAD5-AS1, OR3A4 and some other long non-coding RNAs participate in this process. In the current review, we describe the role of non-coding RNAs in B cell malignancies.

Immunophenotyping and Transcriptional Profiling of Human Plasmablasts in Dengue

Plasmablasts represent a specialized class of antibody-secreting effector B cells that transiently appear in blood circulation following infection or vaccination. The expansion of these cells generally tends to be massive in patients with systemic infections such as dengue or Ebola that cause hemorrhagic fever. To gain a detailed understanding of human plasmablast responses beyond antibody expression, here, we performed immunophenotyping and RNA sequencing (RNA-seq) analysis of the plasmablasts from dengue febrile children in India. We found that plasmablasts expressed several adhesion molecules and chemokines or chemokine receptors that are involved in endothelial interactions or homing to inflamed tissues, including skin, mucosa, and intestine, and upregulated the expression of several cytokine genes that are involved in leukocyte extravasation and angiogenesis. These plasmablasts also upregulated the expression of receptors for several B-cell prosurvival cytokines that are known to be induced robustly in systemic viral infections such as dengue, some of which generally tend to be relatively higher in patients manifesting hemorrhage and/or shock than in patients with mild febrile infection. These findings improve our understanding of human plasmablast responses during the acute febrile phase of systemic dengue infection. IMPORTANCE Dengue is globally spreading, with over 100 million clinical cases annually, with symptoms ranging from mild self-limiting febrile illness to more severe and sometimes life-threatening dengue hemorrhagic fever or shock, especially among children. The pathophysiology of dengue is complex and remains poorly understood despite many advances indicating a key role for antibody-dependent enhancement of infection. While serum antibodies have been extensively studied, the characteristics of the early cellular factories responsible for antibody production, i.e., plasmablasts, are only beginning to emerge. This study provides a comprehensive understanding of the transcriptional profiles of human plasmablasts from dengue patients.

Known and potential molecules associated with altered B cell development leading to predominantly antibody deficiencies

Predominantly antibody deficiencies (PADs) encompass a heterogeneous group of disorders characterized by low immunoglobulin serum levels in the presence or absence of peripheral B cells. Clinical presentation of affected patients may include recurrent respiratory and gastrointestinal infections, invasive infections, autoimmune manifestations, allergic reactions, lymphoproliferation, and increased susceptibility to malignant transformation. In the last decades, several genetic alterations affecting B-cell development/maturation have been identified as causative of several forms of PADs, adding important information on the genetic background of PADs, which in turn should lead to a better understanding of these disorders and precise clinical management of affected patients. This review aimed to present a comprehensive overview of the known and potentially involved molecules in the etiology of PADs to elucidate the pathogenesis of these disorders and eventually offer a better prognosis for affected patients.

Regulation of B Lymphocyte Development by Histone H2A Deubiquitinase BAP1

BAP1 is a deubiquitinase (DUB) of the Ubiquitin C-terminal Hydrolase (UCH) family that regulates gene expression and other cellular processes, via deubiquitination of histone H2AK119ub and other substrates. BAP1 is an important tumor suppressor in human, expressed and functional across many cell-types and tissues, including those of the immune system. B lymphocytes are the mediators of humoral immune response, however the role of BAP1 in B cell development and physiology remains poorly understood. Here we characterize a mouse line with a selective deletion of BAP1 within the B cell lineage (Bap1fl/fl mb1-Cre) and establish a cell intrinsic role of BAP1 in the regulation of B cell development. We demonstrate a depletion of large pre-B cells, transitional B cells, and mature B cells in Bap1fl/fl mb1-Cre mice. We characterize broad transcriptional changes in BAP1-deficient pre-B cells, map BAP1 binding across the genome, and analyze the effects of BAP1-loss on histone H2AK119ub levels and distribution. Overall, our work establishes a cell intrinsic role of BAP1 in B lymphocyte development, and suggests its contribution to the regulation of the transcriptional programs of cell cycle progression, via the deubiquitination of histone H2AK119ub.

Dynamic Intracellular Metabolic Cell Signaling Profiles During Ag-Dependent B-Cell Differentiation

Human B-cell differentiation has been extensively investigated on genomic and transcriptomic grounds; however, no studies have accomplished so far detailed analysis of antigen-dependent maturation-associated human B-cell populations from a proteomic perspective. Here, we investigate for the first time the quantitative proteomic profiles of B-cells undergoing antigen-dependent maturation using a label-free LC-MS/MS approach applied on 5 purified B-cell subpopulations (naive, centroblasts, centrocytes, memory and plasma B-cells) from human tonsils (data are available via ProteomeXchange with identifier PXD006191). Our results revealed that the actual differences among these B-cell subpopulations are a combination of expression of a few maturation stage-specific proteins within each B-cell subset and maturation-associated changes in relative protein expression levels, which are related with metabolic regulation. The considerable overlap of the proteome of the 5 studied B-cell subsets strengthens the key role of the regulation of the stoichiometry of molecules associated with metabolic regulation and programming, among other signaling cascades (such as antigen recognition and presentation and cell survival) crucial for the transition between each B-cell maturation stage.

Mutagenicity monitoring in humans: Global versus specific origin of mutations

An underappreciated aspect of human mutagenicity biomonitoring is tissue specificity reflected in different assays, especially those that measure events that can only occur in developing bone marrow (BM) cells. Reviewed here are 9 currently-employed human mutagenicity biomonitoring assays. Several assays measure chromosome-level events in circulating T-lymphocytes (T-cells), i.e., traditional analyses of aberrations, translocation studies involving chromosome painting and fluorescence in situ hybridization (FISH) and determinations of micronuclei (MN). Other T-cell assays measure gene mutations. i.e., hypoxanthine-guanine phosphoriboslytransferase (HPRT) and phosphoribosylinositol glycan class A (PIGA). In addition to the T-cell assays, also reviewed are those assays that measure events in peripheral blood cells that necessarily arose in BM cells, i.e., MN in reticulocytes; glycophorin A (GPA) gene mutations in red blood cells (RBCs), and PIGA gene mutations in RBC or granulocytes. This review considers only cell culture- or cytometry-based assays to describe endpoints measured, methods, optimal sampling times, and sample summaries of typical quantitative and qualitative results. However, to achieve its intended focus on the target cells where events occur, kinetics of the cells of peripheral blood that derive at some point from precursor cells are reviewed to identify body sites and tissues where the genotoxic events originate. Kinetics indicate that in normal adults, measured events in T-cells afford global assessments of in vivo mutagenicity but are not specific for BM effects. Therefore, an agent's capacity for inducing mutations in BM cells cannot be reliably inferred from T-cell assays as the magnitude of effect in BM, if any, is unknown. By contrast, chromosome or gene level mutations measured in RBCs/reticulocytes or granulocytes must originate in BM cells, i.e. in RBC or granulocyte precursors, thereby making them specific indicators for effects in BM. Assays of mutations arising directly in BM cells may quantitatively reflect the mutagenicity of potential leukemogenic agents.

X-linked Agammaglobulinemia Presenting with Multiviral Pneumonia

X-linked agammaglobulinemia (XLA) is a primary humoral immunodeficiency characterized by severe hypogammaglobulinemia and increased risk of infection. The genetic condition results from a mutation in the Bruton tyrosine kinase (BTK) gene located on the X chromosome leading to a near absence of B cells. Patients affected by XLA are most commonly predisposed to frequent and severe bacterial infections. However, here we report the case of a 20-year-old male with XLA who presented with viral pneumonia with multiple pathogens. This coexistence has been rarely reported. The patient received intravenous immunoglobulin therapy with noted significant improvement in the two weeks of follow-up. His clinical history supports the hypothesis of increased susceptibility to viral pathogens in the absence of immunoglobulin therapy. The humoral defect is the cornerstone of this phenomenon. This case presents the importance of multiviral causes for patients with recurrent episodes of pneumonia in an immunocompromised state.

Low-dose rituximab every 6 months for the treatment of acetylcholine receptor-positive refractory generalized myasthenia gravis

INTRODUCTION

In this prospective, open-label study we explore the effectiveness of low-dose rituximab every 6 months in treating refractory generalized myasthenia gravis (GMG).

METHODS

Twelve patients with acetylcholine receptor (AChR)-positive refractory GMG were enrolled for the study. The primary endpoint was the change in quantitative myasthenia gravis (QMG) score from baseline to the study end. Secondary endpoints included changes in manual muscle testing (MMT), MG-Related Activities of Daily Living (MG-ADL), and 15-item Quality-of-Life (MGQOL-15) scores, as well as prednisolone reduction.

RESULTS

MG decreased from 18.25 ± 4.03 to 8.42 ± 3.99 (P = .0001), MMT from 27.50 ± 17.78 to 4.58 ± 4.34 (P = .0001), ADL from 8.50 ± 2.84 to 1.17 ± 1.27 (P < .0001), MGQOL-15 from 37.25 ± 13.78 to 17.50 ± 9.73 (P = .0015), and prednisolone dose from 29.38 ± 11.92 mg/day to 8.86 ± 1.88 mg/day (P ≤ .01).

DISCUSSION

Low-dose rituximab every 6 months is effective in treating refractory GMG patients.

Immunogenetics of marsupial B-cells

Marsupials and eutherians are mammals that differ in their physiological traits, predominately their reproductive and developmental strategies; eutherians give birth to well-developed young, while marsupials are born highly altricial after a much shorter gestation. These developmental traits also result in differences in the development of the immune system of eutherian and marsupial species. In eutherians, B-cells are the key to humoral immunity as they are found in multiple lymphoid organs and have the unique ability to mediate the production of antigen-specific antibodies in the presence of extracellular pathogens. The development of B-cells in marsupials has been reported and hypothesised to be similar to that of eutherians, except that haematopoiesis occurs in the liver, postpartum, until the bone marrow fully matures. In eutherians, specific genes are linked to specific stages in B-cell development, maturation, and differentiation processes, and have been identified including immunoglobulins (heavy and light chains), cluster of differentiation markers (CD10, 19, 34 and CD79α/β), signal transduction molecules (BTK, Lyn and Syk) and transcriptional regulators (EBF1, E2A, and Pax5). This review aims to discuss the known similarities and differences between marsupial and eutherian B-cells, in regards to their genetic presence, homology, and developmental stages, as well as to highlight the areas requiring further investigation. By enhancing our understanding of the genes that are involved with B-cells in the marsupial lineage, it will, in turn, aid our understanding of the marsupial immune system and support the development of specific immunological reagents for research and wildlife conservation purposes.

Belimumab alters transitional B-cell subset proportions in patients with stable systemic lupus erythematosus

OBJECTIVE

We evaluated the effects of the B-cell activating factor (BAFF)-targeting antibody Belimumab on human nonmemory B-cell pools. Human B-cell pools were identified using surface markers adapted from mouse studies that specifically assessed reductions in immature B cells due to BAFF depletion. Patients with systemic lupus erythematosus (SLE) have high levels of both BAFF and immature B cells. Mechanistic mouse studies provide a framework for understanding human responses to therapies that target B cells.

METHODS

Peripheral blood mononuclear cells were isolated from healthy donors and SLE patients on Belimumab or standard-of-care therapy (SCT). Cells were stained for flow cytometry to identify B-cell subsets based on CD21/CD24. Differences in subset proportions were determined by one-way ANOVA and Tukey's post hoc test.

RESULTS

Patients treated with Belimumab show alterations in the nonmemory B-cell pool characterized by a decrease in the Transitional 2 (T2) subset (p = 0.002), and an increase in the proportion of Transitional 1 (T1) cells (p = 0.005) as compared with healthy donors and SCT patients. The naïve B-cell compartment showed no significant differences between the groups (p = 0.293).

CONCLUSION

Using a translational approach, we show that Belimumab-mediated BAFF depletion reduces the T2 subset in patients, similar to observations in mouse models with BAFF depletion.

Mutations in topoisomerase IIβ result in a B cell immunodeficiency

B cell development is a highly regulated process involving multiple differentiation steps, yet many details regarding this pathway remain unknown. Sequencing of patients with B cell-restricted immunodeficiency reveals autosomal dominant mutations in TOP2B. TOP2B encodes a type II topoisomerase, an essential gene required to alleviate topological stress during DNA replication and gene transcription, with no previously known role in B cell development. We use Saccharomyces cerevisiae, and knockin and knockout murine models, to demonstrate that patient mutations in TOP2B have a dominant negative effect on enzyme function, resulting in defective proliferation, survival of B-2 cells, causing a block in B cell development, and impair humoral function in response to immunization.

Topoisomerases are required to release topological stress on DNA during replication and transcription. Here, Broderick et al. report genetic variants in TOP2B that cause a syndromic B cell immunodeficiency associated with reduced TOP2B function, defects in B cell development and B cell activation.

Long-term tolerability, safety and efficacy of rituximab in neuromyelitis optica spectrum disorder: a prospective study

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is a B-cell-mediated disease with autoimmunity towards the astrocyte water channel aquaporin-4 (AQP-4) in the central nervous system.

OBJECTIVE

To assess the long-term safety and efficacy in NMOSD patients receiving maintenance therapy with B-cell-depleting agent rituximab for more than 2 years.

METHOD

NMOSD patients were included prospectively from 2014 to 2018 and received continuous cycles of rituximab infusions biannually. Incidence of adverse events (AE), serious AEs (SAE), and infusion-related AEs were evaluated through monthly phone calls and neurological examination every 4 months.

RESULTS

A total of 44 NMOSD patients were included, of those 30 were treatment naive (68%). The mean age was 37.2 years with 79.5% females. With overall observation period of 31.6 ± 7.3 months (24-48 months), tolerability was assessed as satisfactory in most cases. We observed infusion reactions (mostly mild) in 31.8% of patients and 31.8% never experienced any AEs after a mean 5.1 cycles of rituximab therapy. Rituximab was also beneficial in terms of improvement in relapse rate (from 0.26 ± 0.54 to 0, P = 0.003) and Expanded Disability Status Scale (from 4.1 ± 1.8 to 3.1 ± 1.8, P < 0.001). Stratification according to AQP4-IgG serostatus showed no difference between groups.

CONCLUSION

Rituximab treatment is well tolerated, safe, and efficacious with a minor risk of mild infusion reactions for NMOSD patients.

B lymphocyte subsets and outcomes in patients with an initial diagnosis of transient hypogammaglobulinemia of infancy

PURPOSE

Transient hypogammaglobulinemia of infancy (THI) is a common immunodeficiency, but definitive diagnosis can only be made retrospectively. While the pathogenesis is still unknown, abnormalities have been reported in the B cell compartment. In this study, we analysed the B cell subsets of patients with an initial THI diagnosis (n = 20) and compared them with those of healthy age-matched Turkish children (n = 72).

METHODS

Flow cytometric analyses of the B subsets were performed by staining with anti-CD27-PE, anti-CD19-PerCP, anti-IgD-FITC and anti-IgM-APC antibodies.

RESULTS

During a median follow-up of 6.6 years, 13 patients whose IgG levels had normalized before they reached four years of age were diagnosed with definitive THI. The memory subsets of these patients were lower but not statistically different from the healthy controls (HC). The remaining seven patients had prolonged hypogammaglobulinemia after the age of four and had significantly lower memory B cell subsets compared to the HC. On follow-up, these patients had not experienced recurrent infections or autoimmunity. Re-evaluation of patients' B cell subsets six years later showed that the memory B cell ratios had increased to levels comparable to HC, despite the patients still having mildly low IgG levels.

CONCLUSION

Patients with prolonged hypogammaglobulinemia had lower levels of memory B cells despite having a similar clinical course to patients who had been diagnosed with definitive THI. This subgroup of putative THI patients poses a diagnostic and classification dilemma. Our results suggested that these patients' memory B cells and IgG levels may recover over time.

Humoral Immune Reconstitution Kinetics after Allogeneic Hematopoietic Stem Cell Transplantation in Children: A Maturation Block of IgM Memory B Cells May Lead to Impaired Antibody Immune Reconstitution

Although T cell immune reconstitution after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been well studied, long-term B cell immune reconstitution remains less characterized. We evaluated humoral immune reconstitution among 71 pediatric allo-HSCT recipients. Although tetanus toxoid antibody levels were normal at 1 year after allo-HSCT, antipolysaccharide carbohydrate antibodies remained persistently low for up to 5 years. While naive B cell counts normalized by 6 months, IgM memory B cell deficiency persisted for up to 2 years (P = .01); switched memory B cell deficiency normalized by 1 year after allo-HSCT. CD4⁺ T cell immune reconstitution correlated with that of switched memory B cells as early as 6 months after allo-HSCT (r = .55, P = .002) but did not correlate with IgM memory B cells at any time point after allo-HSCT. Taken together, this suggests that allo-HSCT recipients have impaired antibody immune reconstitution, mainly due to IgM memory B cell maturation block, compared with more prompt T cell-dependent switched memory cell immune reconstitution. We further explored other factors that might affect humoral immune reconstitution. The use of total body irradiation was associated with lower naive B cells counts at 6 months after HSCT (P = .04) and lower IgM (P = .008) and switched (P = .003) memory B cells up to 2 years. Allo-HSCT recipients with extensive chronic graft-versus-host disease had lower IgM memory B cell counts (P = .03) up to 2 years after allo-HSCT. The use of cord blood was associated with better naive (P = .01), IgM (P = .0005), and switched memory (P = .006) B cells immune reconstitution. These findings may inform future prophylaxis and treatment strategies regarding risk of overwhelming infection, graft-versus-host disease, and post-allogeneic HSCT revaccination.

Role of B Cell Development Marker CD10 in Cancer Progression and Prognosis

The human CD10 antigen is a single pass, type II transmembrane, 100 kD cell surface glycoprotein belonging to peptidase M13 family. Identified in common acute lymphoblastic leukemia as a cancer specific antigen, CD10 is a cell surface ectoenzyme widely expressed on different types of cells. Earlier, it was used only as a cell surface marker to identify and differentiate between haematological malignancies. Later, reported to be present in various malignancies, it is thought to play significant role in cancer development and progression. Regulated expression of CD10 is necessary for angiogenesis and so forth. However its expression level is found to be deregulated in different cancers. In some cancers, it acts as tumor suppressor and inhibits tumor progression whereas in others it has tumor promoting tendency. However, its role in tumorigenesis remains unclear. This review summarises structural features, functions, and probable role of CD10 in cancer development.

Phenotypic and Functional Comparison of Class Switch Recombination Deficiencies with a Subgroup of Common Variable Immunodeficiencies

Primary antibody deficiencies (PADs) are the most common immunodeficiency in humans, characterized by low levels of immunoglobulins and inadequate antibody responses upon immunization. These PADs may result from an early block in B cell development with a complete absence of peripheral B cells and lack of immunoglobulins. In the presence of circulating B cells, some PADs are genetically caused by a class switch recombination (CSR) defect, but in the most common PAD, common variable immunodeficiency (CVID), very few gene defects have as yet been characterized despite various phenotypic classifications. Using a functional read-out, we previously identified a functional subgroup of CVID patients with plasmablasts (PBs) producing IgM only. We have now further characterized such CVID patients by a direct functional comparison with patients having genetically well-characterized CSR defects in CD40L, activation-induced cytidine deaminase (AID) and uracil N-glycosylase activity (UNG). The CSR-like CVID patients showed a failure in B cell activation patterns similar to the classical AID/UNG defects in three out of five CVID patients and distinct more individual defects in the two other CVID cases when tested for cellular activation and PB differentiation. Thus, functional categorization of B cell activation and differentiation pathways extends the expected variation in CVID to CSR-like defects of as yet unknown genetic etiology.

The B-cell compartment in antibody-deficient infants and young children - developing common variable immunodeficiency or transient immune maturation?

Background

Hypogammaglobulinemia in early childhood is a common feature characterized by distinct intrinsic and extrinsic factors leading to disturbed peripheral blood lymphocyte homeostasis. Detailed flow cytometric immunophenotyping of the peripheral blood B cell compartment is an informative tool for delineating disturbed generation of B cell subpopulations crucial for the diagnosis of hypogammaglobulinemia in young children.

Methods

We analyzed by flow cytometry the proportions and absolute values of total, naïve, memory - non-switched and switched, transitional and immature B lymph cells as well as plasmablasts in the peripheral blood of 50 hypogammaglobulinemic children aged from 3 to 50 months.

Results

Beyond physiological, age-related changes within the B cell pool, a proportion of children manifested defective differentiation into switched memory and accumulation of CD21lo immature B cells.

Conclusions

Dynamic shifts within B cell subpopulations of the immature immune system being most prominent during the first two years of life contribute to the age-related developmental abnormalities of the B cell compartment. Therefore, a reliable diagnosis of common variable immunodeficiency (CVID) in young hypogammaglobulinemic children cannot yet be established despite their clinical and immunological phenotypes sharing common features with this primary immunodeficiency.

How to use immunoglobulin levels in investigating immune deficiencies

Children are often referred to immunologists for the evaluation of reduced serum immunoglobulins. Knowledge of the immunoglobulin levels in healthy children of different ages is necessary when estimating immunological deficiency states of various kinds. After the measurement of the serum levels of the three major isotypes, examination of the capacity of the child to form antibodies to several antigens is a reasonable next step in the evaluation. We can rely on vaccine responses to make the distinction between significant primary immunodeficiency diseases and transiently low immunoglobulin levels. On the other hand, normal values of IgM, IgG and IgA are not always enough to exclude a more serious condition. Regardless of immunoglobulin concentrations, if a child's history indicates that further evaluation is warranted, a complete humoral immunity study should be carried out, including IgG subclasses, specific antibody responses and identification of B lymphocyte populations.

Plasma cells in primary melanoma. Prognostic significance and possible role of IgA

Melanoma is not only one of the most immunogenic cancers but also one of the most effective cancers at subverting host immunity. The role of T lymphocytes in tumor immunity has been extensively studied in melanoma, whereas less is known about the importance of B lymphocytes. The effects of plasma cells (PCs), in particular, are still obscure. The aim of this study was to characterize pathological features and clinical outcome of primary cutaneous melanomas associated with PCs. Moreover, we investigated the origins of the melanoma-associated PCs. Finally, we studied the outcome of patients with primary melanomas with PCs. We reviewed 710 melanomas to correlate the presence of PCs with histological prognostic markers. Immunohistochemistry for CD138 and heavy and light chains was performed in primary melanomas (PM) and in loco-regional lymph nodes (LN), both metastatic and not metastatic. In three PM and nine LN with frozen material, VDJ-rearrangement was analyzed by Gene Scan Analysis. Survival analysis was performed on a group of 85 primary melanomas >2 mm in thickness. Forty-one cases (3.7%) showed clusters/sheets of PCs. PC-rich melanomas occurred at an older age and were thicker, more often ulcerated and more mitotically active (P<0.05). PCs were polyclonal and often expressed IgA in addition to IgG. In LN, clusters/sheets of IgA+ PCs were found both in the sinuses and subcapsular areas. Analysis of VDJ-rearrangements showed the IgA to be oligoclonal. Melanomas with clusters/sheets of PCs had a significantly worse survival compared with melanomas without PCs while, interestingly, melanomas with sparse PCs were associated with a better clinical outcome (P=0.002). In conclusion, melanomas with sheets/clusters of PCs are associated with worse prognosis. IgG and IgA are the isotypes predominantly produced by these PCs. IgA oligoclonality suggests an antigen-driven response that facilitates melanoma progression by a hitherto unknown mechanism.

Practice parameter for the diagnosis and management of primary immunodeficiency

The American Academy of Allergy, Asthma & Immunology (AAAAI) and the American College of Allergy, Asthma & Immunology (ACAAI) have jointly accepted responsibility for establishing the "Practice parameter for the diagnosis and management of primary immunodeficiency." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion.

Value of allohaemagglutinins in the diagnosis of a polysaccharide antibody deficiency

Polysaccharide antibody deficiency is characterized by a poor or absent antibody response after vaccination with an unconjugated pneumococcal polysaccharide vaccine. Allohaemagglutinins (AHA) are antibodies to A or B polysaccharide antigens on the red blood cells, and are often used as an additional or alternative measure to assess the polysaccharide antibody response. However, few studies have been conducted to establish the clinical significance of AHA. To investigate the value of AHA to diagnose a polysaccharide antibody deficiency, pneumococcal polysaccharide antibody titres and AHA were studied retrospectively in 180 subjects in whom both tests had been performed. Receiver operating characteristic curves for AHA versus the pneumococcal vaccine response as a marker for the anti-polysaccharide immune response revealed an area under the curve between 0·5 and 0·573. Sensitivity and specificity of AHA to detect a polysaccharide antibody deficiency, as diagnosed by vaccination response, were low (calculated for cut-off 1/4-1/32). In subjects with only low pneumococcal antibody response, the prevalence of bronchiectasis was significantly higher than in subjects with only low AHA (45·5 and 1·3%, respectively) or normal pneumococcal antibody response and AHA (2·4%). A logistic regression model showed that low pneumococcal antibody response but not AHA was associated with bronchiectasis (odds ratio 46·2). The results of this study do not support the routine use of AHA to assess the polysaccharide antibody response in patients with suspected immunodeficiency, but more studies are warranted to clarify the subject further.

X-linked Hyper-IgM Syndrome with Bronchiectasis

The X-linked hyper-immunoglobulin M syndrome (HIGM-1) is a rare genetic disorder characterized by elevated serum IgM levels and low to undetectable levels of serum IgG, IgA and IgE. These patients characteristically present with recurrent sinopulmonary infections and recurrent diarrhea. They also have high susceptibility for Pneumocystis jiroveci (PJ) pneumonia. Herein, we report a case of HGM-1 in a 5-year-old boy who presented with bronchiectasis and, possibly, PJ pneumonia. The diagnosis was established on the basis of clinical features, immune profile, whole blood flow cytometry and history of two male sibling's death due to recurrent pneumonia and diarrhea.

B-lymphocyte lineage cells and the respiratory system

Adaptive humoral immune responses in the airways are mediated by B cells and plasma cells that express highly evolved and specific receptors and produce immunoglobulins of most isotypes. In some cases, such as autoimmune diseases or inflammatory diseases caused by excessive exposure to foreign antigens, these same immune cells can cause disease by virtue of overly vigorous responses. This review discusses the generation, differentiation, signaling, activation, and recruitment pathways of B cells and plasma cells, with special emphasis on unique characteristics of subsets of these cells functioning within the respiratory system. The primary sensitization events that generate B cells responsible for effector responses throughout the airways usually occur in the upper airways, tonsils, and adenoid structures that make up the Waldeyer ring. On secondary exposure to antigen in the airways, antigen-processing dendritic cells migrate into secondary lymphoid organs, such as lymph nodes, that drain the upper and lower airways, and further B-cell expansion takes place at those sites. Antigen exposure in the upper or lower airways can also drive expansion of B-lineage cells in the airway mucosal tissue and lead to the formation of inducible lymphoid follicles or aggregates that can mediate local immunity or disease.

Controversies in IgG replacement therapy in patients with antibody deficiency diseases

This Current perspectives article will review and highlight the importance of accurate diagnosis of patients who have failed to produce specific antibodies to naturally encountered foreign proteins or polysaccharides or after vaccination and the appropriate institution of immunoglobulin replacement therapy. The field of primary immunodeficiency disease (PIDD) has expanded remarkably since the early descriptions 6 decades ago. With greater recognition and advanced cellular and molecular diagnostic technology, new entities and single-gene defects in patients with PIDD are rapidly being defined. This, combined with treatment advances and newborn screening for severe combined immunodeficiency, has resulted in improved outcomes and survival and even permanent cures. Awareness of PIDD has also increased, but the guidelines for recognition remain to be validated. The zeal for registering and enrolling patients has potentially created a large body of "patients" treated with immunoglobulin replacement unnecessarily. The complexity, diversity, and availability of laboratory testing have brought awareness of PIDD to the forefront, but because of an absence of standardization of certain assays, concerns about the correct diagnosis and appropriate treatment have increased. We hope to refocus the discussion on identifying clear laboratory and clinical guidelines for the establishment of an accurate diagnosis of antibody deficiency, its rationale, and, where indicated, institution of safe treatment.

Biology and bioinformatics of myeloma cell

Multiple myeloma (MM) is a plasma cell disorder that occurs in about 10% of all hematologic cancers. The majority of patients (99%) are over 50 years of age when diagnosed. In the bone marrow (BM), stromal and hematopoietic stem cells (HSCs) are responsible for the production of blood cells. Therefore any destruction or/and changes within the BM undesirably impacts a wide range of hematopoiesis, causing diseases and influencing patient survival. In order to establish an effective therapeutic strategy, recognition of the biology and evaluation of bioinformatics models for myeloma cells are necessary to assist in determining suitable methods to cure or prevent disease complications in patients. This review presents the evaluation of molecular and cellular aspects of MM such as genetic translocation, genetic analysis, cell surface marker, transcription factors, and chemokine signaling pathways. It also briefly reviews some of the mechanisms involved in MM in order to develop a better understanding for use in future studies.

Identification of B cell defects using age-defined reference ranges for in vivo and in vitro B cell differentiation

Primary immunodeficiencies consist to a large extent of B cell defects, as indicated by inadequate Ab levels or response upon immunization. Many B cell defects have not yet been well characterized. Our objective was to create reliable in vivo and in vitro assays to routinely analyze human B cell differentiation, proliferation, and Ig production and to define reference ranges for different age categories. The in vitro assays were applied to classify the developmental and/or functional B cell defects in patients previously diagnosed with common variable immunodeficiency. Apart from standard immunophenotyping of circulating human B cell subsets, an in vitro CFSE dilution assay was used for the assessment of proliferative capacity comparing T cell-dependent and T cell-independent B cell activation. Plasmablast/plasma cell differentiation was assessed by staining for CD20, CD38, and CD138, and measurement of in vitro Ig secretion. At young age, B cells proliferate upon in vitro activation, but neither differentiate nor produce IgG. These latter functions reached adult levels at 5 and 10 y of age for T cell-dependent versus T cell-independent stimulations, respectively. The capacity of B cells to differentiate into plasmablasts and to produce IgG appeared to be contained within the switched memory B cell pool. Using these assays, we could categorize common variable immunodeficiency patients into subgroups and identified a class-switch recombination defect caused by an UNG mutation in one of the patients. We defined age-related reference ranges for human B cell differentiation. Our findings indicate that in vivo B cell functionality can be tested in vitro and helps to diagnose suspected B cell defects.

Age-matched reference values for B-lymphocyte subpopulations and CVID classifications in children

Age-matched reference values are generally presented with 5th and 95th percentiles as 'normal' reference range. However, they are mostly determined in relatively small groups, which renders this presentation inaccurate. We determined reference values for B-lymphocyte subpopulations in healthy children with the statistical method of tolerance intervals that deals far better with the relatively small numbers tested, and compared these to the cut-off values used in the currently used EUROclass classification for common variable immunodeficiency disorders (CVID) in children. CVID is a heterogeneous group of primary immunodeficiency diseases characterized by low serum immunoglobulin levels and inadequate response to vaccination. Disease-modifying heterozygous amino acid substitutions in TACI are found in around ±10% of CVID patients. Interestingly, we found that age is the primary determinant of TACI-expression on B-lymphocytes, independent of switched memory B-lymphocyte numbers. Immunophenotyping of B-lymphocyte subpopulations is increasingly used to classify patients with CVID into subgroups with different clinical prognosis according to the composition of their B-lymphocyte compartment. These classifications were mainly developed with data obtained in adults. Because of the maturing paediatric immune system, they may not be equally applicable in children: our and other age-matched reference values show great changes in the composition of the B-lymphocyte compartment during development. Although the greatest changes in B-lymphocyte subpopulations occur below the age of 2 years, when the diagnosis of CVID cannot yet be made, it is likely that a classification developed in adults cannot be used to classify the prognosis of children.

Novel sequencing-based strategies for high-throughput discovery of genetic mutations underlying inherited antibody deficiency disorders

Human inherited antibody deficiency disorders are generally caused by mutations in genes involved in the pathways regulating B-cell class switch recombination; DNA damage repair; and B-cell development, differentiation, and survival. Sequencing a large set of candidate genes involved in these pathways appears to be a highly efficient way to identify novel mutations. Herein we review several high-throughput sequencing approaches as well as recent improvements in target gene enrichment technologies. Systematic improvement of enrichment and sequencing methods, along with refinement of the experimental process is necessary to develop a cost-effective high-throughput resequencing assay for a large cohort of patient samples. The Hyper-IgM/CVID chip is one example of a resequencing platform that may be used to identify known or novel mutations in patents with various types of inherited antibody deficiency.