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Rheumatoid arthritis (RA) is a systemic autoimmune disease driven by highly active autoantibody-producing B cells. Activation of B cells is maintained within ectopic germinal centres found in affected joints. Fibroblast-like synoviocytes (FLS) present in inflamed joints support B-cell survival, activation, and differentiation. CD27+ memory B cells and naive B cells show very different responses to activation, particularly by CD40 ligand (CD40L). We show that FLS-dependent activation of human B cells is dependent on interleukin-6 (IL-6) and CD40L. FLS have been shown to activate both naive and memory B cells. Whether the activating potential of FLS is different for naive and memory B cells has not been investigated. Our results suggest that FLS-induced activation of B cells is dependent on IL-6 and CD40L. While FLS are able to induce plasma cell differentiation, isotype switching, and antibody production in memory B cells, the ability of FLS to activate naive B cells is significantly lower., (© 2024 The Author(s). Immunology published by John Wiley & Sons Ltd.)

Background: We examined the physicochemical properties of IgD-type M protein from 10 patients with IgD-type M protein and those with other types of M protein., Methods: Identification of the L-chain type by routine methods (Immunoelectrophoresis: IEP, Immunofixation electrophoresis; IFE), detection of IgD-IgG complexes and the changes in the mobility by treatment with acid., Results: Identification of the L-chain type by both IEP and IFE was impossible. Only one patient revealed the possibility of IgD-IgG complex bands in 6 of the 10 samples. Changes in mobility by treatment with acid were observed in 8 of the 10 samples of IgD-type M protein., Conclusions: These abnormalities are caused by the primary structure of IgD, which may be related to the well-known weak reactivity with L-chain antibody.

The Asian seabass (Lates calcarifer) faces significant disease threats, which are exacerbated by intensive farming practices and environmental changes. Therefore, understanding its immune system is crucial. The current study presents a comprehensive analysis of immune-related genes in Asian seabass peripheral blood leukocytes (PBLs) using Iso-seq technology, identifying 16 key pathways associated with 7857 immune-related genes, comprising 634 unique immune-related genes. The research marks the first comprehensive report on the entire immunoglobulin repertoire in Asian seabass, revealing specific characteristics of immunoglobulin heavy chain constant region transcripts, including IgM (Cμ, ighm), IgT (Cτ, ight), and IgD (Cδ, ighd). The study confirms the presence of membrane-bound form, ighm mb , ight mb , ighd mb of IgM, IgT and IgD and secreted form, ighm sc and ight sc of IgM and IgT, respectively, with similar structural patterns and conserved features in amino acids across immunoglobulin molecules, including cysteine residues crucial for structural integrity observed in other teleost species. In response to bacterial infections by Flavobacterium covae (formerly F. columnare genomovar II) and Streptococcus iniae, both secreted and membrane-bound forms of IgM (ighm mb and ighm sc ) and IgT (ight mb and ight sc ) show significant expression, indicating their roles in systemic and mucosal immunity. The expression of membrane-bound form IgD gene, ighd mb , predominantly exhibits targeted upregulation in PBLs, suggesting a regulatory role in B cell-mediated immunity. The findings underscore the dynamic and tissue-specific expression of immunoglobulin repertoires, ighm mb , ighm sc , ight mb , ight sc and ighd mb in Asian seabass, indicating a sophisticated immune response to bacterial pathogens. These findings have practical implications for fish aquaculture, and disease control strategies, serving as a valuable resource for advancing research in Asian seabass immunology., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, heavy chain genes of IgD and IgT were sequenced and characterized their gene expression in rock bream (Oplegnathus fasciatus). Rock bream (RB)-IgD cDNA is 3319 bp in length and encodes a leader region, variable domains, a μ1 domain, and seven constant domains (CH1-CH7). A membrane-bound (mIgT) and secretory form (sIgT) of RB-IgT cDNAs are 1902 bp and 1689 bp in length, respectively, and encode a leader region, variable domains, four constant domains (CH1-CH4) and C-terminus. Their predicted 3D-structure and phylogenetic relation were similar to those of other teleost. In healthy fish, RB-IgD and mIgT gene expressions were higher in major lymphoid organs and blood, while RB-sIgT gene was more highly expressed in midgut. IgT expressing cells were detected in melano-macrophage centers (MMC) of head kidney in immunohistochemistry analysis. Under immune stimulation in vitro, RB-IgD and IgT gene expressions were upregulated in head kidney and spleen cells by bovine serum albumin or a rock bream iridovirus (RBIV) vaccine. In vivo, their expressions were significantly upregulated in head kidney, blood, and gill upon vaccination. Especially, RB-mIgT gene expression in head kidney and blood was upregulated at day 3 after vaccination while upregulated at earlier time point of day 1 by challenge with RBIV. This may suggest that memory cells might be produced during the primary response by vaccination and rapidly proliferated by secondary immune response by viral infection. RB-sIgT gene expression was highly upregulated in peripheral blood in vaccinated fish after viral infection, indicating that IgT plays an important role in systemic immune response as well as mucosal immune system. Our findings provide information on the role of RB-IgT in adaptive immunity during vaccination and viral infection in the vaccinated fish., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Autoimmune hepatitis (AIH) is a chronic, inflammatory liver disease of unknown aetiology which requires lifelong immunosuppression. Most therapeutic and outcome studies of AIH have been conducted predominantly in Caucasian (European Ancestry, EA) cohorts, with the exclusion of African American (AA) patients due to inadequate sample size. It is known that AA patients have a severe phenotype of autoimmune diseases and demonstrate a poor response to conventional medical therapy. Understanding cellular and molecular pathways which determine AIH severity and progression in AA patients is likely to lead to the discovery of novel, personalised and better tolerated therapies. The aim of the study is to determine the distinct effector B cell phenotypes which contribute to disease severity and progression of AIH in AA children as compared to their EA cohorts. PBMCs were isolated from blood samples collected from patients visiting Children's Healthcare of Atlanta (CHOA) and were grouped into AA, ( n  = 12), EA, ( n  = 11) and controls ( n  = 12) and were processed for flow cytometry. Markers of B cell development, maturation and activation were assessed namely CD19, CD21, IgD, CD27, CD38, CD11c, CD24, CD138. AA children with AIH demonstrated an expansion of CD19 + ve, Activated Naïve (aN), (CD19 + IgD - /CD27 - Double Negative (DN 2 ) ([CD19+/IgD - /CD27 ++ CD38 ++ ) cells. Plasmablasts were significantly higher along with Signalling Lymphocytic activation molecule F7 (SLAMF7). Unswitched memory [CD19+] IgD + CD27 + (USM) B cells were significantly contracted in AA patients with AIH. B cell phenotyping reveals a distinct profile in AA AIH patients with a major skewing towards the expansion of effector pathways which have been previously characterised in severe SLE in AA patients. These results suggest that the quantification and therapeutic target of B cell pathway could contribute substantially to the clinical approach to AIH especially in the AA population.

In chronic lymphocytic leukemia (CLL), the B cell receptor (BCR) plays a critical role in disease development and progression, as indicated by the therapeutic efficacy of drugs blocking BCR signaling. However, the mechanism(s) underlying BCR responsiveness are not completely defined. Selective engagement of membrane IgM or IgD on CLL cells, each coexpressed by more than 90% of cases, leads to distinct signaling events. Since both IgM and IgD carry the same antigen-binding domains, the divergent actions of the receptors are attributed to differences in immunoglobulin (Ig) structure or the outcome of signal transduction. We showed that IgM, not IgD, level and organization associated with CLL-cell birth rate and the type and consequences of BCR signaling in humans and mice. The latter IgM-driven effects were abrogated when BCR signaling was inhibited. Collectively, these studies demonstrated a critical, selective role for IgM in BCR signaling and B cell fate decisions, possibly opening new avenues for CLL therapy.

A considerable proportion of peripheral B cells is autoreactive, and it is unclear how the activation of such potentially harmful cells is regulated. In this study, we show that the different activation thresholds or IgM and IgD BCRs adjust B cell activation to the diverse requirements during development. We rely on the autoreactive 3-83 model BCR to generate and analyze mice expressing exclusively autoreactive IgD BCRs on two different backgrounds that determine two stages of autoreactivity, depending on the presence or absence of the cognate Ag. By comparing these models with IgM-expressing control mice, we found that, compared with IgM, IgD has a higher activation threshold in vivo, as it requires autoantigen to enable normal B cell development, including allelic exclusion. Our data indicate that IgM provides the high sensitivity required during early developmental stages to trigger editing of any autoreactive specificities, including those enabling weak interaction with autoantigen. In contrast, IgD has the unique ability to neglect weakly interacting autoantigens while retaining reactivity to higher-affinity Ag. This IgD function enables mature B cells to ignore autoantigens while remaining able to efficiently respond to foreign threats., (Copyright © 2022 by The American Association of Immunologists, Inc.)

Background: In the nation-wide double-blind cluster-randomised Finnish Invasive Pneumococcal disease trial (FinIP, ClinicalTrials.gov NCT00861380, NCT00839254), we assessed the indirect impact of the 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against five pneumococcal disease syndromes., Methods: Children 6 weeks to 18 months received PHiD-CV10 in 48 clusters or hepatitis B/A-vaccine as control in 24 clusters according to infant 3+1/2+1 or catch-up schedules in years 2009-2011. Outcome data were collected from national health registers and included laboratory-confirmed and clinically suspected invasive pneumococcal disease (IPD), hospital-diagnosed pneumonia, tympanostomy tube placements (TTP) and outpatient antimicrobial prescriptions. Incidence rates in the unvaccinated population in years 2010-2015 were compared between PHiD-CV10 and control clusters in age groups <5 and ≥5 years (5-7 years for TTP and outpatient antimicrobial prescriptions), and in infants <3 months. PHiD-CV10 was introduced into the Finnish National Vaccination Programme (PCV-NVP) for 3-month-old infants without catch-up in 9/2010., Results: From 2/2009 to 10/2010, 45398 children were enrolled. Vaccination coverage varied from 29 to 61% in PHiD-CV10 clusters. We detected no clear differences in the incidence rates between the unvaccinated cohorts of the treatment arms, except in single years. For example, the rates of vaccine-type IPD, non-laboratory-confirmed IPD and empyema were lower in PHiD-CV10 clusters compared to control clusters in 2012, 2015 and 2011, respectively, in the age-group ≥5 years., Conclusions: This is the first report from a clinical trial evaluating the indirect impact of a PCV against clinical outcomes in an unvaccinated population. We did not observe consistent indirect effects in the PHiD-CV10 clusters compared to the control clusters. We consider that the sub-optimal trial vaccination coverage did not allow the development of detectable indirect effects and that the supervening PCV-NVP significantly diminished the differences in PHiD-CV10 vaccination coverage between the treatment arms., Competing Interests: The Finnish Institute for Health and Welfare (THL) received funding for the conduct of the FinIP study from the GSK group of companies. AAP, HN, ER, and JJ are employees of THL. HR-K was an employee of THL at the time of study conduct. DB and LS are employees of the GSK group of companies; MM was an employee of the GSK group of companies. MM, DB and LS have shares in the GSK group of companies. We note that several authors have an affiliation to the commercial funder of this research study: GlaxoSmithKline Biologicals SA. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Since the identification of a functional Cδ gene in ostriches, immunoglobulin (Ig) D has been considered to be an extremely evolutionarily conserved Ig isotype besides the IgM found in all classes of jawed vertebrates. However, in contrast to IgM (which remains stable over evolutionary time), IgD shows considerable structural plasticity among vertebrate species and, moreover, its functions are far from elucidated even in humans and mice. Recently, several studies have shown that high expression of the IgD-B-cell receptor (IgD-BCR) may help physiologically autoreactive B cells survive in peripheral lymphoid tissues thanks to unresponsiveness to self-antigens and help their entry into germinal centers to "redeem" autoreactivity via somatic hypermutation. Other studies have demonstrated that secreted IgD may enhance mucosal homeostasis and immunity by linking B cells with basophils to optimize T-helper-2 cell-mediated responses and to constrain IgE-mediated basophil degranulation. Herein, we review the new discoveries on IgD-encoding genes in jawed vertebrates in the past decade. We also highlight advances in the functions of the IgD-BCR and secreted IgD in humans and mice., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In order to better understand how the immune system interacts with environmental triggers to produce organ-specific disease, we here address the hypothesis that B and plasma cells are free to migrate through the mucosal surfaces of the upper and lower respiratory tracts, and that their total antibody repertoire is modified in a common respiratory tract disease, in this case atopic asthma. Using Adaptive Immune Receptor Repertoire sequencing (AIRR-seq) we have catalogued the antibody repertoires of B cell clones retrieved near contemporaneously from multiple sites in the upper and lower respiratory tract mucosa of adult volunteers with atopic asthma and non-atopic controls and traced their migration. We show that the lower and upper respiratory tracts are immunologically connected, with trafficking of B cells directionally biased from the upper to the lower respiratory tract and points of selection when migrating from the nasal mucosa and into the bronchial mucosa. The repertoires are characterized by both IgD-only B cells and others undergoing class switch recombination, with restriction of the antibody repertoire distinct in asthmatics compared with controls. We conclude that B cells and plasma cells migrate freely throughout the respiratory tract and exhibit distinct antibody repertoires in health and disease., Competing Interests: SHK receives consulting fees from Northrop Grumman. KBH receives consulting fees from Prellis Biologics. YJ, CC, TGJ and RH are employed by Bristol Myers Squibb. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor has declared past collaborations with one of the authors SHK at the time of this review., (Copyright © 2021 Ohm-Laursen, Meng, Hoehn, Nouri, Jiang, Clouser, Johnstone, Hause, Sandhar, Upton, Chevretton, Lakhani, Corrigan, Kleinstein and Gould.)

Increased IgE is a typical feature of allergic rhinitis. Local class-switch recombination has been intimated but B cell precursors and mechanisms remain elusive. Here we describe the dynamics underlying the generation of IgE-antibody secreting cells (ASC) in human nasal polyps (NP), mucosal tissues rich in ASC without germinal centers (GC). Using V H next generation sequencing, we identified an extrafollicular (EF) mucosal IgD+ naïve-like intermediate B cell population with high connectivity to the mucosal IgE ASC. Mucosal IgD+ B cells, express germline epsilon transcripts and predominantly co-express IgM. However, a small but significant fraction co-express IgG or IgA instead which also show connectivity to ASC IgE. Phenotypically, NP IgD+ B cells display an activated profile and molecular evidence of BCR engagement. Transcriptionally, mucosal IgD+ B cells reveal an intermediate profile between naïve B cells and ASC. Single cell IgE ASC analysis demonstrates lower mutational frequencies relative to IgG, IgA, and IgD ASC consistent with IgE ASC derivation from mucosal IgD+ B cell with low mutational load. In conclusion, we describe a novel mechanism of GC-independent, extrafollicular IgE ASC formation at the nasal mucosa whereby activated IgD+ naïve B cells locally undergo direct and indirect (through IgG and IgA), IgE class switch., (© 2021. The Author(s).)

Human B cells could be divided into four classical subsets based on CD27 and immunoglobulin (Ig)D expression. Distinct from the other three well-studied subsets, CD27 - IgD - B cells, also termed as double-negative (DN) B cells, have long been neglected. However, in recent years emerging evidence shows that DN B cells are unique memory B cells with important functions. They are expanded in a variety of diseases, especially in autoimmune diseases, contributing to the disease pathogenesis. Here, we briefly review the studies on DN B cells, including their origins, characteristics, subsets and roles in diseases, to try to bring new insights into this under-recognized B cell subset., (© 2021 British Society for Immunology.)

Vaccination and infection promote the formation, tissue distribution, and clonal evolution of B cells, which encode humoral immune memory. We evaluated pediatric and adult blood and deceased adult organ donor tissues to determine convergent antigen-specific antibody genes of similar sequences shared between individuals. B cell memory varied for different pathogens. Polysaccharide antigen-specific clones were not exclusive to the spleen. Adults had higher clone frequencies and greater class switching in lymphoid tissues than blood, while pediatric blood had abundant class-switched convergent clones. Consistent with reported serology, prepandemic children had class-switched convergent clones to severe acute respiratory syndrome coronavirus 2 with weak cross-reactivity to other coronaviruses, while adult blood or tissues showed few such clones. These results highlight the prominence of early childhood B cell clonal expansions and cross-reactivity for future responses to novel pathogens., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Tissue-based T cells are important effectors in the prevention and control of mucosal viral infections; less is known about tissue-based B cells. We demonstrate that B cells and antibody-secreting cells (ASCs) are present in inflammatory infiltrates in skin biopsy specimens from study participants during symptomatic herpes simplex virus 2 (HSV-2) reactivation and early healing. Both CD20+ B cells, most of which are antigen inexperienced based on their coexpression of IgD, and ASCs - characterized by dense IgG RNA expression in combination with CD138, IRF4, and Blimp-1 RNA - were found to colocalize with T cells. ASCs clustered with CD4+ T cells, suggesting the potential for crosstalk. HSV-2-specific antibodies to virus surface antigens were also present in tissue and increased in concentration during HSV-2 reactivation and healing, unlike in serum, where concentrations remained static over time. B cells, ASCs, and HSV-specific antibody were rarely detected in biopsies of unaffected skin. Evaluation of samples from serial biopsies demonstrated that B cells and ASCs followed a more migratory than resident pattern of infiltration in HSV-affected genital skin, in contrast to T cells. Together, these observations suggest the presence of distinct phenotypes of B cells in HSV-affected tissue; dissecting their role in reactivation may reveal new therapeutic avenues to control these infections.

The clinical application of monoclonal antibodies (mAbs) has revolutionized the field of cancer therapy, as it has enabled the successful treatment of previously untreatable types of cancer. Different mechanisms play a role in the anti-tumour effect of mAbs. These include blocking of tumour-specific growth factor receptors or of immune modulatory molecules as well as complement and cell-mediated tumour cell lysis. Thus, for many mAbs, Fc-mediated effector functions critically contribute to the efficacy of treatment. As immunoglobulin (Ig) isotypes differ in their ability to bind to Fc receptors on immune cells as well as in their ability to activate complement, they differ in the immune responses they activate. Therefore, the choice of antibody isotype for therapeutic mAbs is dictated by its intended mechanism of action. Considering that clinical efficacy of many mAbs is currently achieved only in subsets of patients, optimal isotype selection and Fc optimization during antibody development may represent an important step towards improved patient outcome. Here, we discuss the current knowledge of the therapeutic effector functions of different isotypes and Fc-engineering strategies to improve mAbs application., (© 2020 British Society for Immunology.)

Immunoglobulins are glycoproteins which are produced as membrane-bound receptors on B-cells or in a secreted form, known as antibodies. In teleosts, three immunoglobulin isotypes, IgM, IgT, and IgD, are present, each comprising two identical heavy and two identical light polypeptide chains. The basic mechanisms for generation of immunoglobulin diversity are similar in teleosts and higher vertebrates. The B-cell pre-immune repertoire is diversified by VDJ recombination, junctional flexibility, addition of nucleotides, and combinatorial association of light and heavy chains, while the post-immune repertoire undergoes somatic hypermutation during clonal expansion. Typically, the teleost immunoglobulin heavy chain gene complex has a modified translocon arrangement where the Dτ-Jτ-Cτ cluster of IgT is generally located between the variable heavy chain (VH) region and the Dμ/δ-Jμ/δ-Cμ-Cδ gene segments, or within the set of VH gene segments. However, multiple genome duplication and deletion events and loss of some individual genes through evolution has complicated the IgH gene organization. The IgH gene arrangement allows the expression of either IgT or IgM/IgD. Alternative splicing is responsible for the regulation of IgM/IgD expression and the secreted versus transmembrane forms of IgT, IgD, and IgM. The overall structure of IgM and IgT is usually conserved across species, whereas IgD has a large variety of structures. IgM is the main effector molecule in both systemic and mucosal immunity and shows a broad range of concentrations in different teleost species. Although IgM is usually present in higher concentrations under normal conditions, IgT is considered the main mucosal Ig.

Primary HIV infection (PHI) and subsequent chronic infection alter B-cell compartment. However, longitudinal analysis defining the dynamics of B-cell alterations are still limited. We longitudinally studied B-cell subsets in individuals followed for 1 year after PHI (n = 40). Treated and untreated chronic HIV infected (n = 56) and HIV-uninfected individuals (n = 58) were recruited as reference groups at the Manhiça District in Mozambique. B cells were analyzed by multicolor flow-cytometry. Anti-HIV humoral response and plasma cytokines were assessed by ELISA or Luminex-based technology. A generalized activation of B cells induced by HIV occurs early after infection and is characterized by increases in Activated and Tissue-like memory cells, decreases in IgM-IgD- (switched) and IgM-only B cells. These alterations remain mostly stable until chronic infection and are reverted in part by ART. In contrast, other parameters followed particular dynamics: PD-1 expression in memory cells decreases progressively during the first year of infection, Transitional B cells expand at month 3-4 after infection, and Marginal zone-like B cells show a late depletion. Plasmablasts expand 2 months after infection linked to plasma viral load and anti-p24 IgG3 responses. Most of well-defined changes induced by HIV in B-cell activation and memory subsets are readily observed after PHI, lasting until ART initiation. However, subsequent changes occur after sustained viral infection. These data indicate that HIV infection impacts B cells in several waves over time, and highlight that early treatment would result in beneficial effects on the B-cell compartment., Competing Interests: Unrelated to this work, JB is CEO and founder of AlbaJuna Therapeutics, S.L. and JC is CSO and founder of AlbaJuna Therapeutics, S.L. The remaining authors declare that the research was conducted in the absence of any direct commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Jiménez, Pastor, Urrea, Rodríguez de la Concepción, Parker, Fuente-Soro, Jairoce, Mandomando, Carrillo, Naniche and Blanco.)

It is now appreciated that in addition to their role in humoral immunity, B cells also exert regulatory mechanisms that lead to attenuation of inflammatory responses. The concept of B-cell regulation became well recognized when mice deficient in B cells due to genetic disruption were shown to be refractory to recovery from the signs of experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. This seminal study spurred the search for B-cell regulatory phenotypes and mechanisms of action. Our approach was to utilize differential B-cell depletion with anti-CD20 to retain B cells whose presence were required to achieve EAE recovery. Utilizing flow cytometry, adoptive cell therapy and genetic approaches, we discovered a new B-cell subset that, upon adoptive transfer into B cell-deficient mice, was sufficient to promote EAE recovery. This B-cell subset is IgM + , but due to low/negative IgD cell surface expression, it was named B-cell IgD low (BD L ). Mechanistically, we found that in the absence of BD L , the absolute cell number of CD4 + Foxp3 + T regulatory cells (Treg), essential for immune tolerance, was significantly reduced. Furthermore, we found that BD L expression of glucocorticoid-induced tumor necrosis factor ligand (GITRL) was essential for induction of Treg proliferation and maintenance of their homeostasis. Thus, we have identified a new B-cell subset that is critical for immunological tolerance through interactions with Treg., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

To assess how B cell phenotype analysis correlates with antigen responses in patients with class switch recombination defects (CSRD) we quantified memory B cells by flow-cytometry and immunized CSRD patients with the neoantigen bacteriophage phiX174 (phage). CSRD patients showed uniformly absent or markedly reduced switched memory B cells (IgM - IgD - CD27 + ). CD40L patients had reduced CD27 + memory B cells (both non-switched and switched). In NEMO patients, results varied depending on the IKKγ gene variant. Three of four AID patients had normal percentages of CD27 + memory B cells while CD27 + IgM - IgD - switched memory B cells were markedly reduced in all AID patients. Antibody response to phage was remarkably decreased with lack of memory amplification and class-switching in immunized CD40L, UNG deficient, and NEMO patients. Distinct B-cell phenotype pattern correlated with abnormal antibody responses to a T-cell dependent neoantigen, representing a powerful tool to identify CSRD patients., (Copyright © 2020 Elsevier Inc. All rights reserved.)

B-cell IgD Low (BD L ) B cells have been shown to promote immunological tolerance by inducing proliferation of CD4 + Foxp3 + T-regulatory cells (Treg) in a glucocorticoid-induced tumor necrosis factor receptor-related protein ligand (GITRL, Tnfsf18)-dependent manner. BD L cells constitute a small subset of splenic B lymphocytes that, in mice, are characterized by the B220 + IgM int CD21 int CD23 + CD93 - IgD low/- cell surface expression profile. In this chapter, we show the flow cytometry gating strategy developed to identify and purify BD L . In addition, we describe an in vitro assay and two in vivo assays to assess BD L regulatory activity by quantitating Treg expansion/proliferation and indicate how they can be used in mouse models of disease. Collectively, these methods are useful to track and quantitate BD L and Treg numbers and assess their regulatory activity in inflammatory disease models.

Introduction: The Autoimmunity Screening for Kids (ASK) study is a large scale pediatric screening study in Colorado for celiac disease (CD) and type 1 diabetes. This is a report of the CD outcomes for the first 9,973 children screened through ASK., Methods: ASK screens children aged 1-17 years for CD using 2 highly sensitive assays for tissue transglutaminase autoantibodies (TGA): a radiobinding (RBA) assay for IgA TGA and an electrochemiluminescence (ECL) assay that detects all TGA isotypes. Children who test positive on either assay are asked to return for confirmatory testing. Those with a confirmed RBA TGA level ≥ 0.1 (twice the upper limit of normal) are referred to the Colorado Center for Celiac Disease for further evaluation; all others are referred to primary care., Results: Of the initial 9,973 children screened, 242 children were TGA+ by any assay. Of those initially positive, 185 children (76.4%) have completed a confirmation blood draw with 149 children (80.5%) confirming positive by RBA TGA. Confirmed RBA TGA+ was associated with a family history of CD (odds ratio [OR] = 1.83; 95% confidence interval 1.06-3.16), non-Hispanic white ethnicity (OR = 3.34; 2.32-4.79), and female sex (OR = 1.43; 1.03-1.98). Gastrointestinal symptoms of CD, assessed at the initial screening, were reported equally often among the RBA TGA+ vs TGA- children (32.1% vs 30.5%, P = 0.65)., Discussion: The initial results of this ongoing mass-screening program confirm a high prevalence of undiagnosed CD autoimmunity in a screened US population. Symptoms at initial screening were not associated with TGA status (see Visual abstract, Supplementary Digital Content 5, http://links.lww.com/AJG/B587)., (Copyright © 2020 by The American College of Gastroenterology.)

Due to direct contact with aquatic environment, mucosal surfaces of teleost fish are continuously exposed to a vast number of pathogens and also inhabited by high densities of commensal microbiota. The B cells and immunoglobulins within the teleost mucosa-associated lymphoid tissues (MALTs) play key roles in local mucosal adaptive immune responses. So far, three Ig isotypes (i.e., IgM, IgD, and IgT/Z) have been identified from the genomic sequences of different teleost fish species. Moreover, teleost Igs have been reported to elicit mammalian-like mucosal immune response in six MALTs: gut-associated lymphoid tissue (GALT), skin-associated lymphoid tissue (SALT), gill-associated lymphoid tissue (GIALT), nasal-associated lymphoid tissue (NALT), and the recently discovered buccal and pharyngeal MALTs. Critically, analogous to mammalian IgA, teleost IgT represents the most ancient Ab class specialized in mucosal immunity and plays indispensable roles in the clearance of mucosal pathogens and the maintenance of microbiota homeostasis. Given these, this review summarizes the current findings on teleost Igs, MALTs, and their immune responses to pathogenic infection, vaccination and commensal microbiota, with the purpose of facilitating future evaluation and rational design of fish vaccines., (Copyright © 2020 Yu, Wang, Huang, Ding and Xu.)

Three classes of immunoglobulins have been identified in Teleosts: IgM, IgT/Z and IgD. They are fundamental for fish immune responses and, therefore, their functional activities are heavily investigated. In this paper, we describe the identification of a new IgD/IgT chimera in sea bass (Dicentrarchus labrax) from a gills transcriptome. This transcript joined the first six constant domains of the IgD chain with the two terminal constant domains of IgT, generating a long in-frame coding sequence with a junction between the canonical δ6 exon splicing donor site and the τ3 exon splicing acceptor site. Studies performed on genomic DNA confirmed the presence of the sequence and identifies and intronic region of 656 bp within this joining region. The basal expression of the IgD/IgT chimera was investigated both in silico and in vivo: high level of expression was found in gills, gut and head kidney. Moreover, IgD/IgT transcripts were up-regulated after in vitro stimulation of sea bass HK leukocytes with LPS. The IgD/IgT chimera was found also in two congener species, Morone saxatilis and Morone chrysops. It is not possible to have a precise idea on the evolutionary scenario that lead to the appearance of this sequence due to the lack of genomic information, but we could speculate that an ancestral duplication of the entire IgH locus was followed by the chimerization of Cδ/Cτ in one of the two loci. Finally, the IgD/IgT high basal expression in tissues and organs fundamental for sea bass immune response and its modulation after LPS stimulation provide a very preliminary indication that this unusual Ig variant could have a functional activity., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Proliferative kidney disease (PKD), caused by the myxozoan Tetracapsuloides bryosalmonae, is one of the most serious parasitic diseases of salmonids in which outbreaks cause severe economic constraints for the aquaculture industry and declines of wild species throughout Europe and North America. Given that rainbow trout (Oncorhynchus mykiss) is one of the most widely farmed freshwater fish and an important model species for fish immunology, most of the knowledge on how the fish immune response is affected during PKD is from this organism. Once rainbow trout are infected, PKD pathogenesis results in a chronic kidney immunopathology mediated by decreasing myeloid cells and increasing lymphocytes. Transcriptional studies have revealed the regulation of essential genes related to T-helper (Th)-like functions and a dysregulated B-cell antibody type response. Recent reports have discovered unique details of teleost B-cell differentiation and functionality and characterized the differential immunoglobulin (Ig)-mediated response. These studies have solidified the rainbow trout T. bryosalmonae system as a sophisticated disease model capable of feeding key advances into mainstream immunology and have contributed essential information to design novel parasite disease prevention strategies. In our following perspective, we summarize these efforts to evaluate the immune mechanisms of rainbow trout during PKD pathogenesis., (© 2020 The Authors. Parasite Immunology published by John Wiley & Sons Ltd.)

Humoral immune responses at mucosal surfaces have historically focused on IgA. Growing evidence highlights the complexity of IgA-inducing pathways and the functional impact of IgA on mucosal commensal bacteria. In the gut, IgA contributes to the establishment of a mutualistic host-microbiota relationship that is required to maintain homeostasis and prevent disease. This Review discusses how mucosal IgA responses occur in an increasingly complex humoral defence network that also encompasses IgM, IgG and IgD. Aside from integrating the protective functions of IgA, these hitherto neglected mucosal antibodies may strengthen the communication between mucosal and systemic immune compartments.

IgD-Fc-Ig fusion protein, a new biological agent, is constructed by linking a segment of human IgD-Fc with a segment of human IgG1-Fc, which specifically blocks the IgD-IgDR pathway and selectively inhibits the abnormal proliferation, activation, and differentiation of T cells. In this study we investigated whether IgD-Fc-Ig exerted therapeutic effects in collagen-induced arthritis (CIA) rats. CIA rats were treated with IgD-Fc-Ig (1, 3, and 9 mg/kg) or injected with biological agents etanercept (3 mg/kg) once every 3 days for 40 days. In the PBMCs and spleen lymphocytes of CIA rats, both T and B cells exhibited abnormal proliferation; the percentages of CD3 + total T cells, CD3 + CD4 + Th cells, CD3 + CD4 + CD25 + -activated Th cells, Th1(CD4 + IFN-γ + ), and Th17(CD4 + IL-17 + ) were significantly increased, whereas the Treg (CD4 + CD25 + Foxp3 + ) cell percentage was decreased. IgD-Fc-Ig administration dose-dependently decreased the indicators of arthritis; alleviated the histopathology of spleen and joint; reduced serum inflammatory cytokines levels; decreased the percentages of CD3 + total T cells, CD3 + CD4 + Th cells, CD3 + CD4 + CD25 + -activated Th cells, Th1 (CD4 + IFN-γ + ), and Th17(CD4 + IL-17 + ); increased Treg (CD4 + CD25 + Foxp3 + ) cell percentage; and down-regulated the expression of key molecules in IgD-IgDR-Lck-NF-κB signaling (p-Lck, p-ZAP70, p-P38, p-NF-κB65). Treatment of normal T cells with IgD (9 μg/mL) in vitro promoted their proliferation. Co-treatment with IgD-Fc-Ig (0.1-10 μg/mL) dose-dependently decreased IgD-stimulated T cell subsets percentages and down-regulated the IgD-IgDR-Lck-NF-κB signaling. In summary, this study demonstrates that IgD-Fc-Ig alleviates CIA and regulates the functions of T cells through inhibiting IgD-IgDR-Lck-NF-κB signaling.

Recent data show that B cells and plasma cells located in tumours or in tumour-draining lymph nodes can have important roles in shaping antitumour immune responses. In tumour-associated tertiary lymphoid structures, T cells and B cells interact and undergo cooperative selection, specialization and clonal expansion. Importantly, B cells can present cognate tumour-derived antigens to T cells, with the functional consequences of such interactions being shaped by the B cell phenotype. Furthermore, the isotype and specificity of the antibodies produced by plasma cells can drive distinct immune responses. Here we summarize our current knowledge of the roles of B cells and antibodies in the tumour microenvironment. Moreover, we discuss the potential of using immunoglobulin repertoires as a source of tumour-specific receptors for immunotherapy or as biomarkers to predict the efficacy of immunotherapeutic interventions.

Columnaris disease, induced by Flavobacterium columnare, seriously affects the health of freshwater fish species and damages the mucosal tissues, such as the fins, skin, and gills. Teleosts represent the first bony vertebrate to contain both innate and adaptive immune responses against pathogens. So far, three immunoglobulin isotypes (IgM, IgD, and IgT/IgZ) have been identified in teleost fish, and IgT in mucosal tissues of teleost fish was reported to perform a similar function to IgA in mammals during parasitic infection. However, very limited information is known about the function of IgT in gill mucosal tissues during bacterial infection. In the present study, rainbow trout (Oncorhynchus mykiss) was infected with F. columnare (Fc) via immersion. After Fc infection, the gill structure of rainbow trout showed serious hyperplasia symptoms on the secondary lamellae at 12 h post infection (hpi). Moreover, the mRNA expression levels of NOS2 and cathelicidin-1 were significantly upregulated immediately at 12 hpi and showed high expression throughout the experiment. IgT and IgM showed much higher mRNA expression levels at 28 days post infection (dpi) and 75 dpi, while IgD only showed high mRNA expression levels at 28 dpi. Importantly, the accumulation of IgT + B cells and strong bacteria-specific IgT responses were detected in the gill lamellae of both infected fish (28 dpi) and survivor fish (75 dpi). Overall, our results suggest that IgT and IgT + B cells play a central role in the adaptive immune responses of fish gill mucosa against bacterial infection., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The establishment of a diverse B cell antigen receptor (BCR) repertoire by V(D)J recombination also generates autoreactive B cells. Anergy is one tolerance mechanism; it renders autoreactive B cells insensitive to stimulation by self-antigen, whereas Toll-like receptor (TLR) signaling can reactivate anergic B cells. Here, we describe a critical role of the transcription factor Ikaros in controlling BCR anergy and TLR signaling. Mice with specific deletion of Ikaros in mature B cells developed systemic autoimmunity. Ikaros regulated many anergy-associated genes, including Zfp318, which is implicated in the attenuation of BCR responsiveness by promoting immunoglobulin D expression in anergic B cells. TLR signaling was hyperactive in Ikaros-deficient B cells, which failed to upregulate feedback inhibitors of the MyD88-nuclear factor κB signaling pathway. Systemic inflammation was lost on expression of a non-self-reactive BCR or loss of MyD88 in Ikaros-deficient B cells. Thus, Ikaros acts as a guardian preventing autoimmunity by promoting BCR anergy and restraining TLR signaling.

The increasingly recognized role of different types of B cells and plasma cells in protective and pathogenic immune responses combined with technological advances have generated a plethora of information regarding the heterogeneity of this human immune compartment. Unfortunately, the lack of a consistent classification of human B cells also creates significant imprecision on the adjudication of different phenotypes to well-defined populations. Additional confusion in the field stems from: the use of non-discriminatory, overlapping markers to define some populations, the extrapolation of mouse concepts to humans, and the assignation of functional significance to populations often defined by insufficient surface markers. In this review, we shall discuss the current understanding of human B cell heterogeneity and define major parental populations and associated subsets while discussing their functional significance. We shall also identify current challenges and opportunities. It stands to reason that a unified approach will not only permit comparison of separate studies but also improve our ability to define deviations from normative values and to create a clean framework for the identification, functional significance, and disease association with new populations., (Copyright © 2019 Sanz, Wei, Jenks, Cashman, Tipton, Woodruff, Hom and Lee.)

Background and Objectives: The purpose of the study was to evaluate a lyophilized anti-D immunoglobulin preparation to serve as a replacement WHO International Standard for the calibration of potency assays of anti-D immunoglobulin products. Such products are used to prevent haemolytic disease of the foetus and newborn due to maternal alloanti-D., Materials and Methods: The candidate 3rd International Standard for anti-D immunoglobulin (16/332) was evaluated and calibrated against the 2nd International Standard for anti-D immunoglobulin (01/572), along with a coded duplicate, a second candidate preparation (16/278) and a comparability sample (16/272) in an international collaborative study. Twenty of 21 laboratories in 15 countries performed one or more of the three European Pharmacopoeia reference methods., Results: The overall geometric mean potency (from all methods) of the candidate 3rd International Standard, 16/332, was 296·6 IU/ampoule, with inter-laboratory variability, expressed as % GCV, of 4·7%. SE-HPLC of the immunoglobulin preparations demonstrated combined monomeric and dimeric IgG peak areas of >95% for all samples. Accelerated stability studies have shown both 16/332 and 16/278 to be very stable for long-term storage at -20°C., Conclusions: Preparation 16/332 was established by the World Health Organisation Expert Committee on Biological Standardization as the 3rd International Standard for anti-D immunoglobulin with an assigned potency of 297 IU/ampoule., (© 2019 The Authors. Vox Sanguinis published by John Wiley & Sons Ltd on behalf of International Society of Blood Transfusion.)

IgD - CD27 - double negative (DN) B cells with proinflammatory characteristics are abnormally elevated in a proportion of multiple sclerosis (MS) patients. In this study, the origin and selection characteristics of DN B cells were studied in MS patients and healthy controls (HC). Expression of developmental markers on peripheral blood DN, IgD - CD27 + class-switched memory (CSM) and IgD + CD27 - naive B cells of HC ( n = 48) and MS patients ( n = 96) was determined by flow cytometry. High-throughput adaptive immune receptor repertoire sequencing was performed on peripheral blood DN and CSM B cells of HC and MS patients ( n = 3 each). DN B cells from HC and MS patients showed similar phenotypic and Ig repertoire characteristics. Phenotypic analysis indicated a mature state of DN B cells by low CD5, CD10, and CD38 expression. However, the frequency of CD95 + and IgA + cells was lower in DN versus CSM B cells. DN B cells are Ag experienced, as shown by somatic hypermutation of their Ig genes in adaptive immune receptor repertoire sequencing, although they showed a lower mutation load than CSM B cells. Shared clones were found between DN and CSM B cells, although >95% of the clones were unique to each population, and differences in V(D)J usage and CDR3 physicochemical properties were found. Thus, DN B cells arise in HC and MS patients via a common developmental pathway that is probably linked to immune aging. However, DN and CSM B cells develop through unique differentiation pathways, with most DN B cells representing an earlier maturation state., (Copyright © 2019 by The American Association of Immunologists, Inc.)

In contrast to other B-cell antigen receptor (BCR) classes, the function of IgD BCR on mature B cells remains largely elusive as mature B cells co-express IgM, which is sufficient for development, survival, and activation of B cells. Here, we show that IgD expression is regulated by the forkhead box transcription factor FoxO1, thereby shifting the responsiveness of mature B cells towards recognition of multivalent antigen. FoxO1 is repressed by phosphoinositide 3-kinase (PI3K) signaling and requires the lipid phosphatase Pten for its activation. Consequently, Pten-deficient B cells expressing knock-ins for BCR heavy and light chain genes are unable to upregulate IgD. Furthermore, in the presence of autoantigen, Pten-deficient B cells cannot eliminate the autoreactive BCR specificity by secondary light chain gene recombination. Instead, Pten-deficient B cells downregulate BCR expression and become unresponsive to further BCR-mediated stimulation. Notably, we observed a delayed germinal center (GC) reaction by IgD-deficient B cells after immunization with trinitrophenyl-ovalbumin (TNP-Ova), a commonly used antigen for T-cell-dependent antibody responses. Together, our data suggest that the activation of IgD expression by Pten/FoxO1 results in mature B cells that are selectively responsive to multivalent antigen and are capable of initiating rapid GC reactions and T-cell-dependent antibody responses., (© 2019 The Authors. Published under the terms of the CC BY 4.0 license.)

Red Mark Syndrome (RMS) is a skin disease reported from farmed rainbow trout. Since the turn of the millennium it has been spreading through Europe. RMS is probably a bacterial disease caused by a Midichloria-like organism (MLO). It is non-lethal and causes little obvious changes in appetite or behavior but results in red hyperaemic skin lesions, which may lead to economic losses due to downgrading. Here we transfer RMS to naïve specific pathogen free (SPF) fish by cohabitation with RMS-affected seeder fish. During disease development we characterize local cellular immune responses and regulations of immunologically relevant genes in skin of the cohabitants by immunohistochemistry and qPCR. Skin samples from SPF controls and cohabitants (areas with and without lesions) were taken at 18, 61, 82 and 97 days post-cohabitation. Gene expression results showed that lesions had a Th1-type profile, but with concurrent high expression levels of all three classes of immunoglobulins (IgD, IgM and IgT). The marked local infiltration of IgD + cells in the skin lesions as well as a highly up-regulated expression of the genes encoding sIgD and mIgD indicate that this immunoglobulin class plays an important role in skin immunity in general and in RMS pathology in particular. The co-occurrence of an apparent B cell dominated immune reaction with a Th1-type profile suggests that the local production of antibodies is independent of the classical Th2 pathway., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Canine leishmaniosis (CanL) due to Leishmania infantum is characterized by the development of both cellular and humoral immune responses. The dysfunction of T cell-mediated immunity leads to a lack of proliferation of T cells in response to Leishmania antigens with the consequence of parasite dissemination that seems to be related to a T cell exhaustion mediated by regulatory B cells expressing immunoglobulin D (IgD). The aim of this study was to determine and compare the total serum IgD in dogs with clinical leishmaniosis and in clinically healthy dogs., Results: A total of 147 dog sera were studied. All dogs were tested for L. infantum-specific antibodies by quantitative ELISA. Interferon-gamma (IFN-γ) production was also determined by sandwich ELISA after blood stimulation with L. infantum soluble antigen (LSA) or concanavalin A (ConA). The quantification of total IgD was performed using a human IgD sandwich ELISA quantification set. Dogs were classified in three different groups. Group 1 included 40 clinically healthy non-infected dogs, all serologically negative to L. infantum-specific antibodies and non-producers of IFN-γ upon LSA stimulation. Group 2 included 63 clinically healthy infected dogs that were LSA IFN-γ producers (n = 61) and/or IFN-γ non-producers (n = 2) as well as negative to medium seropositive to L. infantum antigen. Finally, Group 3 included 44 dogs with clinical leishmaniosis (IFN-γ producers, n = 23; and IFN-γ non-producers, n = 21) that were negative to highly positive to L. infantum-specific antibodies. No significant differences were observed when the total IgD concentration was compared within groups. Additionally, total IgD of sick IFN-γ producers and IFN-γ non-producers was not significantly different. Finally, total IgD concentration was not statistically related to demographic parameters such as age, sex and breed., Conclusions: The results of this study demonstrated that there were no differences between groups in total serum IgD. Total serum IgD does not appear to be a marker of disease in CanL.

Background: We assessed 2 investigational 11- and 12-valent vaccines, containing capsular polysaccharides of 10 serotypes as in the pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) and CRM 197 -conjugated capsular polysaccharides of serotypes 19A (11-valent) or 19A and 6A (12-valent)., Methods: In this phase II, partially-blind, multicentre study (NCT01204658), healthy infants were randomised (1:1:1:1) to receive 11vPHiD-CV, 12vPHiD-CV, PHiD-CV, or 13-valent CRM 197 -conjugate pneumococcal vaccine (PCV13), at 2, 3, and 4 (primary series), and 12-15 months of age (booster dose), co-administered with DTPa-HBV-IPV/Hib. Confirmatory objectives assessed non-inferiority of investigational vaccines to comparators (PHiD-CV for common serotypes; PCV13 for 19A and 6A), in terms of percentage of infants with pneumococcal antibody concentrations ≥0.2 μg/mL and antibody geometric mean concentrations, post-primary vaccination. Reactogenicity and safety were assessed., Results: 951 children received ≥1 primary dose, 919 a booster dose. Pre-defined immunological non-inferiority criteria were met simultaneously for 9/11 11vPHiD-CV serotypes (all except 23F and 19A) and 10/12 12vPHiD-CV serotypes (all except 19A and 6A); thus, non-inferiority objectives were reached. For each PHiD-CV serotype, percentages of children with antibody concentrations ≥0.2 µg/mL were ≥96.7% post-primary (except 6B [≥75.2%] and 23F [≥81.1%]), and ≥98.1% post-booster vaccination. For each PHiD-CV serotype except serotype 1, ≥81.0% and ≥93.9% of children had opsonophagocytic activity titres ≥8, post-primary and booster vaccination. AEs incidence was similar across all groups. SAEs were reported for 117 children (29 in the 11vPHiD-CV group, 26 in the 12vPHiD-CV group, 38 in the PHiD-CV group and 24 in the PCV13 group); 4 SAEs were considered vaccination-related. No fatal events were recorded., Conclusion: Addition of 19A and 6A CRM 197 -conjugates did not alter immunogenicity of the PHiD-CV conjugates; for both investigational vaccines post-booster immune responses to 10 common serotypes appeared similar to those elicited by PHiD-CV. Safety and reactogenicity profiles of the investigational vaccines were comparable to PHiD-CV. Clinical trial registry: NCT01204658., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Three different immunoglobulin (Ig) isotypes, namely IgM, IgD, and IgT/IgZ have been described in most teleost, among which IgM and IgT are considered crucial in systematic and mucosal immunity, respectively. However, some teleost have no IgT/IgZ and it is unclear how other Ig isotypes interact to perform immune-protective roles in both systematic and mucosal sites. In this study, the complete cDNA sequences of IgM and IgD heavy chains were cloned and analyzed from yellow catfish (Pelteobagrus fulvidraco). The full-length cDNA of Pf-IgM and Pf-IgD heavy chains contained an open reading frame (ORF) of 1710 and 2991 bp encoding a predicted protein of 570 and 997 amino acids, respectively. Tissue-specific expression analysis indicated that both IgM and IgD were highly expressed in kidney and spleen, and higher expression levels were found at zygote and 13th day post hatching during early development. Multiple sequence alignment and phylogenetic analysis showed IgM and IgD of yellow catfish are closely related to other fish of Siluriformes. Moreover, we also constructed the infection model of yellow catfish with bacteria (Flavobacterium columnare G 4 ) for the first time to study the function of Pf-IgM and Pf-IgD heavy chain genes in immune response. Quantitative real-time PCR (qRT-PCR) showed that significantly up-regulated expression of Pf-IgM was not only detected in liver and spleen, but also in mucosal tissues including skin and intestine, while Pf-IgD was just significantly increased in liver and spleen, which might suggest the main immune-protecting roles of IgM in mucosal tissues of yellow catfish., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The disruption of adaptive immune response has adverse effects on the establishment and maintenance of pregnancy. The adaptive immune system is regulated by several types of immune cells. However, there is limited information about cell hierarchy in the adaptive immune response to the establishment and maintenance of pregnancy in women. The assessment of the outcome of pregnancy in primary immunodeficiency diseases could help in understanding the cell hierarchy in the adaptive immune system during pregnancy. Common variable immunodeficiency (CVID) is a heterogeneous adaptive immune system disorder characterized by primary hypogammaglobulinemia. A few studies have previously reported the assessment of the T and B cell subpopulations in CVID patients. However, an assessment of the subpopulations of T and B cells and the outcome of pregnancy in women with CVID has not been reported till date. Most CVID patients show a general decrease in the expression of CD27 in B cells. The assessment of pregnancy and the subpopulations of T and B cells in CVID women with severe reduction in the naïve T and switched B cells could help understand whether these cells are essential for the establishment and maintenance of pregnancy in women., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A substantial fraction of mature naïve B cells recognize endogenous antigens, and this autoreactivity must be controlled to prevent autoantibody secretion. Selective downregulation of the IgM BCR on autoreactive B cells has long been appreciated, and recent findings illustrate how this might impose tolerance. The BCR isotype maintained on autoreactive B cells, IgD, is less sensitive to endogenous antigens than IgM. This reduced sensitivity may be conferred by structural properties of IgD and/or differential association with activating and inhibitory co-receptors. Once activated, autoreactive B cells are normally excluded from rapid plasma cell responses, but they can enter the germinal center and lose their autoreactivity through a mutation-selection process termed clonal redemption., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Although upregulated expression of local IgD has been reported in patients with chronic rhinosinusitis (CRS), its function is unclear., Objective: We sought to explore the expression and function of soluble IgD in patients with CRS, particularly CRS with nasal polyps., Methods: IgD levels in sinonasal mucosa were analyzed by using RT-PCR and ELISA. Numbers and phenotypes of IgD + cells were studied by means of immunohistochemistry, immunofluorescence, and flow cytometry. HMC-1 cells, a human mast cell line, and mast cells purified from eosinophilic polyps were cultured alone or with naive B cells purified from peripheral blood. The antigen specificity of nasal IgD was investigated by using ELISA., Results: The mRNA expression of immunoglobulin heavy constant delta gene, numbers of IgD + cells, and protein levels of secretory IgD in sinonasal mucosa were increased in patients with CRS with or without nasal polyps compared with control subjects. Numbers of IgD + plasmablasts were increased in both eosinophilic and noneosinophilic polyps, whereas numbers of IgD + mast cells were only increased in eosinophilic polyps. Cross-linking IgD induced serum preincubated HMC-1 cells and polyp mast cells to produce B-cell activating factor, IL-21, IL-4, and IL-13 and to promote IgM, IgG, IgA, and IgE production from B cells. In eosinophilic polyps expression of those B cell-stimulating factors in mast cells and close contact between mast cells and B cells were found. Moreover, positive correlations of total IgD levels with total IgE levels and eosinophilia and upregulation of specific IgD against house dust mites were discovered in eosinophilic polyps., Conclusion: IgD-activated mast cells can facilitate IgE production and eosinophilic inflammation in patients with CRS with nasal polyps., (Copyright © 2018 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Objectives: Behçet's disease (BD) is an autoinflammatory disorders mainly characterised by recurrent oral aphthosis, genital ulcers, and uveitis. The involvement of immunoglobulin D (IgD) in BD physiopathology is still unclear. The aim of our study was to assess the role of IgD in BD by comparing circulating levels of IgD in a cohort of BD patients and healthy controls (HC), as well as by correlating IgD levels with BD activity and different clinical presentations., Methods: Serum IgD and SAA levels were analysed by ELISA assay in ninety-nine serum samples collected from 72 BD patients and in 29 HC subjects., Results: Serum concentration of IgD were higher in BD patients compared with HC (p=0.029), in patients with high serum amyloid A (SAA) levels compared with patients with normal SAA levels (p=0.035), and among subjects with active mucocutaneous involvement compared with other patients (p=0.036). No correlations were identified between IgD serum levels and disease activity assessed by the BD current activity form (BDCAF) (p=0.640). No differences were observed in the IgD serum levels between patients with and without specific disease manifestations. Increased SAA levels (Odds Ratio = 3.978, CI: 1.356 -11.676) and active mucocutaneous BD manifestations (Odds Ratio = 4.286, CI: 1.192 - 15.407) were associated with a high risk for increased IgD serum levels., Conclusions: Serum IgD levels are significantly increased in BD patients, especially among patients with active mucocutaneous manifestations, suggesting a possible role of IgD in BD pathogenesis and in the onset of mucosal and skin lesions.

B cells thwart antigenic aggressions by releasing immunoglobulin M (IgM), IgG, IgA, and IgE, which deploy well-understood effector functions. In contrast, the role of secreted IgD remains mysterious. We found that some B cells generated IgD-secreting plasma cells following early exposure to external soluble antigens such as food proteins. Secreted IgD targeted basophils by interacting with the CD44-binding protein galectin-9. When engaged by antigen, basophil-bound IgD increased basophil secretion of interleukin-4 (IL-4), IL-5, and IL-13, which facilitated the generation of T follicular helper type 2 cells expressing IL-4. These germinal center T cells enhanced IgG1 and IgE but not IgG2a and IgG2b responses to the antigen initially recognized by basophil-bound IgD. In addition, IgD ligation by antigen attenuated allergic basophil degranulation induced by IgE co-ligation. Thus, IgD may link B cells with basophils to optimize humoral T helper type 2-mediated immunity against common environmental soluble antigens., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: Nontypeable Haemophilus influenzae (NTHi) is a commensal in the human nasopharynx and the cause of pneumonia, meningitis, sinusitis, acute exacerbations of chronic obstructive pulmonary disease and acute otitis media (AOM). AOM is the most common ailment for which antibiotics are prescribed in the United States. With the emergence of new strains of antibiotic-resistant bacteria, finding an effective and broad coverage vaccine to protect against AOM-causing pathogens has become a priority. Mouse models are a cost-effective and efficient way to help determine vaccine efficacy. Here, we describe an NTHi AOM model in C57BL/6J mice, which also utilizes a mouse-adapted H1N1 influenza virus to mimic human coinfection., Methodology: We tested our coinfection model using a protein vaccine formulation containing protein D, a well-studied NTHi vaccine candidate that can be found in the 10-valent Streptococcus pneumoniae conjugate vaccine. We verified the usefulness of our mouse model by comparing bacterial loads in the nose and ear between protein D-vaccinated and control mice., Results: While there was no measurable difference in nasal bacterial loads, we did detect significant differences in the bacterial loads of ear washes and ear bullae between vaccinated and control mice., Conclusion: The results from this study suggest that our NTHi AOM coinfection model is useful for assessing protein vaccines.

Background: Pneumococcal conjugate vaccines have potential to prevent significant proportion of childhood pneumonia. Finnish Invasive Pneumococcal disease vaccine trial was designed to assess the vaccine effectiveness (VE) of the 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against several outcomes. We now report results for pneumonia., Methods: In this nationwide, cluster-randomised, double-blind trial, children younger than 19 months received PHiD-CV10 in 52 clusters or hepatitis vaccines as control in 26 clusters. Infants younger than 7 months at the first vaccination received either 3+1 or 2+1 vaccination schedule, children aged 7-11 months received 2+1, and those 12-18 months of age two-dose schedule. All hospitalizations and outpatient visits to hospital associated with ICD-10 codes compatible with pneumonia were identified through the National Care Register and 1-3 frontal chest X-ray images per event were collected. External readers who were unaware of the patients' vaccination status retrospectively interpreted the images. The evaluated outcomes were hospital-diagnosed, hospital-treated pneumonia as primary diagnosis, and radiologically confirmed pneumonia during the blinded, intention-to-treat follow-up period from the first vaccination to the end of 2011. Total VE was calculated as 1 minus rate ratio of all pneumonia episodes., Results: 47 366 children were enrolled from February 2009, to October 2010. VE against all episodes of hospital-diagnosed pneumonia was 27% (95% confidence interval [CI]: 14%, 38%), 32% (95% CI: 3%, 52%), and 23% (95% CI: -5%, 44%) in subjects enrolled at age <7, 7-11, and 12-18 months, respectively. Corresponding rate reductions were 3.4, 4.7, and 2.5 per 1000 person-years. VE estimates against pneumonia with alveolar consolidation or pleural effusion (WHO criteria) in the three cohorts were 45% (95% CI: 26%, 60%), 56% (95% CI: 14%, 77%), and 48% (95% CI: 2%, 73%), respectively., Conclusion: PHiD-CV10 vaccination remarkably reduced disease burden due to pneumonia in infants and young children., Clinical Trial Registration: Main trial NCT00861380, nested carriage and otitis media trial NCT00839254 (ClinicalTrials.gov)., (Copyright © 2018. Published by Elsevier Ltd.)

Despite teleost fish being the first animal group in which all elements of adaptive immunity are present, the lack of follicular structures, as well as the fact that systemic Ab responses rely exclusively on unswitched low-affinity IgM responses, strongly suggests that fish B cell responses resemble mammalian B1 cell responses rather than those of B2 cells. In line with this hypothesis, in the current study, we have identified a homolog of CD5 in teleost fish. This pan-T marker belonging to the scavenger receptor cysteine-rich family of receptors is commonly used in mammals to distinguish a subset of B1 cells. Subsequently, we have demonstrated that a very high percentage of teleost IgM + B cells express this marker, in contrast to the limited population of CD5-expressing B1 cells found in most mammals. Furthermore, we demonstrate that fish IgM + B cells share classical phenotypic features of mammalian B1 cells such as large size, high complexity, high surface IgM, and low surface IgD expression, regardless of CD5 expression. Additionally, fish IgM + B cells, unlike murine B2 cells, also displayed extended survival in cell culture and did not proliferate after BCR engagement. Altogether, our results demonstrate that although fish are evolutionarily the first group in which all the elements of acquired immunity are present, in the absence of follicular structures, most teleost IgM + B cells have retained phenotypical and functional characteristics of mammalian B1 cells., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Background: We report a case of immunoglobulin (Ig) D myeloma with hidden lambda light chains in a patient whose immunofixation test was very difficult to interpret: the IgD reacts with the anti-δ heavy chain antiserum but does not react with anti-lambda antiserum. The band in the D heavy chain lane is unmatched in light chain lanes and the band in lambda light chain lane migrates higher., Methods: To distinguish between heavy chain disease and immunoglobulin with "hidden" light chains, the sample was exposed to a very high concentration of anti-lambda and anti-kappa antisera for 48 hours., Results: The serum immunofixation test of the sample treated with anti-lambda showed a decrease in the intensity of the band corresponding to D heavy chain lane as well as the modification of its mobility confirming the presence of IgD with the hidden lambda light chains., Conclusions: The IgD myeloma with hidden light chains remains a rare entity, hence the interest of sensitizing health professionals to be vigilant and ensure a good diagnosis. The proposed technique is useful, simple, reliable, and less laborious than those previous reported in the literature. Medical laboratories using Sebia-Hydrasys® system should be aware of the described phenomenon in order to avoid identifying an IgD myeloma as a delta heavy chain disease.