Ig Class Research Articles

Identification of Liver Epithelial Cell-derived Ig Expression in μ chain-deficient mice.

Growing evidence indicates that B cells are not the only source of immunoglobulin (Ig). To investigate this discovery further, we used μMT mice, which have a disruption of the first transmembrane exon of the μ heavy chain and do not express the membrane form of IgM. These mice lack mature B cells and thus serve as a good model to explore Ig expression by liver epithelial cells. We found that Ig heavy chains (μ, δ, γ and α) and light chains (κ and λ) were expressed in sorted liver epithelial cells of μMT mice. Surprisingly, each heavy chain class showed its respective variable region sequence characteristics in their variable region, instead of sharing the same VDJ usage, which suggests that class switching does not occur in liver epithelial cells. Moreover, the γ and α chains, but not the μ and δ chains, showed mutations in the variable region, thus indicating that different classes of Ig have different activities. Our findings support the concept that non-B cells, liver epithelial cells here, can produce different classes of Ig.

Molecular cloning and expression analysis IgM, IgD and IgT heavy chain genes in Misgurnus anguillicaudatus

Immunoglobulins (Igs) are essential components of the adaptive immune system in jawed vertebrates, including teleost fish, the oldest bony vertebrate. Three immunoglobulin classes have been identified in teleost species, IgM, IgD and IgT/Z. In this study, we cloned and identified the heavy chain gene sequences of IgM, IgD and IgZ in dojo loach (Misgurnus anguillicaudatus). The cDNA of IgM, IgD and IgZ heavy chain gene in dojo loach consisted of 1963, 3052, 1860bp and encoding 581, 977, 544 amino acid residues, repectively. The structure of thess three Ig classes are comparised of variable region (V) and constant regions (CH): IgM(1V+4CH), IgD (1V+7CH) and IgZ (1V+4CH), which are similar to their counterparts described in other teleosts. The transcriptional level of these three Ig classes were detected by Quantitative real-time PCR (qRT-PCR) in liver, spleen, mesonephros, gills, muscle, intestine, skin, blood and swimmbladder. Interestingly, the expression of IgM and IgD were mainly detected in blood, spleen and mesonephros followed by skin, gills and intestine. However, IgT was highly expressed in intestine, mesonephros, skin and gill, followed by blood and speen. The expression of IgM, IgD and IgZ during dojo loach embryogenesis, and the pattern of expression of these three Ig molecules in dojo loach following the infection with Aeromonas hydrophila are under investaging. This is the first report IgM, IgD and IgZ in M. anguillicaudatus. The prevalence of IgT expression in intestine, skin and gills of fish strongly suggests a prevailing role of IgT in mucosal immunity.

Mediator facilitates transcriptional activation and dynamic long-range contacts at the IgH locus during class switch recombination.

Immunoglobulin (Ig) class switch recombination (CSR) is initiated by the transcription-coupled recruitment of activation-induced cytidine deaminase (AID) to Ig switch regions (S regions). During CSR, the IgH locus undergoes dynamic three-dimensional structural changes in which promoters, enhancers, and S regions are brought to close proximity. Nevertheless, little is known about the underlying mechanisms. In this study, we show that Med1 and Med12, two subunits of the mediator complex implicated in transcription initiation and long-range enhancer/promoter loop formation, are dynamically recruited to the IgH locus enhancers and the acceptor regions during CSR and that their knockdown in CH12 cells results in impaired CSR. Furthermore, we show that conditional inactivation of Med1 in B cells results in defective CSR and reduced acceptor S region transcription. Finally, we show that in B cells undergoing CSR, the dynamic long-range contacts between the IgH enhancers and the acceptor regions correlate with Med1 and Med12 binding and that they happen at a reduced frequency in Med1-deficient B cells. Our results implicate the mediator complex in the mechanism of CSR and are consistent with a model in which mediator facilitates the long-range contacts between S regions and the IgH locus enhancers during CSR and their transcriptional activation.

Human CD4<sup>-</sup> CD8<sup>-</sup> Invariant Natural Killer T Cells Promote IgG Secretion from B Cells Stimulated by Cross-Linking of Their Antigen Receptors

Immunoglobulin (Ig) M production can be induced by the interaction of thymus-independent type-2 (TI-2) antigen (Ag) with B cell Ag receptors (BCRs) without the involvement of conventional T cells; for IgG production through the same process, however, a second signal is required. Previous studies have reported that invariant natural killer T (iNKT) cells may be responsible for the second signal involved in IgG production. In the present study, we addressed whether human iNKT cells could participate in the production of Ig against TI-2 Ag in vitro. Two major distinct subsets of human iNKT cells, CD4+ CD8β- (CD4) and CD4- CD8β- [double negative (DN)] cells, were generated from peripheral blood monocytes from a healthy volunteer. BCR engagement, triggered by anti-IgM antibody stimulation, examined here as a model of BCR engagement triggered by TI-2 Ag, induced abundant IgM production by B cells. Both CD4 and DN iNKT cells reduced IgM production and conversely enhanced IgG production in a dose-dependent manner. In addition, IgG production by CD19+CD27- (naive) and CD19+CD27+ (memory) B cells was predominantly promoted by DNiNKT cells rather than CD4 iNKT cells; nevertheless, IgM production by both B cell subsets was similarly reduced by either subset of iNKT cells. These results suggest that the DN iNKT subsets may preferentially promote Ig class switching by B cells upon stimulation with TI-2 Ag.

DNA-PKcs Is Involved in Ig Class Switch Recombination in Human B Cells.

Nonhomologous end-joining (NHEJ) is one of the major DNA double-strand break repair pathways in mammalian cells and is required for both V(D)J recombination and class switch recombination (CSR), two Ig gene-diversification processes occurring during B cell development. DNA-dependent protein kinase, catalytic subunit (DNA-PKcs) is a component of the classical NHEJ machinery and has a critical function during V(D)J recombination. However, its role in CSR has been controversial. In this study, we examined the pattern of recombination junctions from in vivo-switched B cells from two DNA-PKcs-deficient patients. One of them harbored mutations that did not affect DNA-PKcs kinase activity but caused impaired Artemis activation; the second patient had mutations resulting in diminished DNA-PKcs protein expression and kinase activity. These results were compared with those from DNA-PKcs-deficient mouse B cells. A shift toward the microhomology-based alternative end-joining at the recombination junctions was observed in both human and mouse B cells, suggesting that the classical NHEJ pathway is impaired during CSR when DNA-PKcs is defective. Furthermore, cells from the second patient showed additional or more severe alterations in CSR and/or NHEJ, which may suggest that DNA-PKcs and/or its kinase activity have additional, Artemis-independent functions during these processes.

Epigenetics of Peripheral B-Cell Differentiation and the Antibody Response.

Epigenetic modifications, such as histone post-translational modifications, DNA methylation, and alteration of gene expression by non-coding RNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are heritable changes that are independent from the genomic DNA sequence. These regulate gene activities and, therefore, cellular functions. Epigenetic modifications act in concert with transcription factors and play critical roles in B cell development and differentiation, thereby modulating antibody responses to foreign- and self-antigens. Upon antigen encounter by mature B cells in the periphery, alterations of these lymphocytes epigenetic landscape are induced by the same stimuli that drive the antibody response. Such alterations instruct B cells to undergo immunoglobulin (Ig) class switch DNA recombination (CSR) and somatic hypermutation (SHM), as well as differentiation to memory B cells or long-lived plasma cells for the immune memory. Inducible histone modifications, together with DNA methylation and miRNAs modulate the transcriptome, particularly the expression of activation-induced cytidine deaminase, which is essential for CSR and SHM, and factors central to plasma cell differentiation, such as B lymphocyte-induced maturation protein-1. These inducible B cell-intrinsic epigenetic marks guide the maturation of antibody responses. Combinatorial histone modifications also function as histone codes to target CSR and, possibly, SHM machinery to the Ig loci by recruiting specific adaptors that can stabilize CSR/SHM factors. In addition, lncRNAs, such as recently reported lncRNA-CSR and an lncRNA generated through transcription of the S region that form G-quadruplex structures, are also important for CSR targeting. Epigenetic dysregulation in B cells, including the aberrant expression of non-coding RNAs and alterations of histone modifications and DNA methylation, can result in aberrant antibody responses to foreign antigens, such as those on microbial pathogens, and generation of pathogenic autoantibodies, IgE in allergic reactions, as well as B cell neoplasia. Epigenetic marks would be attractive targets for new therapeutics for autoimmune and allergic diseases, and B cell malignancies.

Green Turtles (Chelonia mydas) Have Novel Asymmetrical Antibodies.

Igs in vertebrates comprise equally sized H and L chains, with exceptions such as H chain-only Abs in camels or natural Ag receptors in sharks. In Reptilia, Igs are known as IgYs. Using immunoassays with isotype-specific mAbs, in this study we show that green turtles (Chelonia mydas) have a 5.7S 120-kDa IgY comprising two equally sized H/L chains with truncated Fc and a 7S 200-kDa IgY comprised of two differently sized H chains bound to L chains and apparently often noncovalently associated with an antigenically related 90-kDa moiety. Both the 200- and 90-kDa 7S molecules are made in response to specific Ag, although the 90-kDa molecule appears more prominent after chronic Ag stimulation. Despite no molecular evidence of a hinge, electron microscopy reveals marked flexibility of Fab arms of 7S and 5.7S IgY. Both IgY can be captured with protein G or melon gel, but less so with protein A. Thus, turtle IgY share some characteristics with mammalian IgG. However, the asymmetrical structure of some turtle Ig and the discovery of an Ig class indicative of chronic antigenic stimulation represent striking advances in our understanding of immunology.

Survival analysis and microarray profiling identify Cd40 as a candidate for the Salmonella susceptibility locus, Ity5.

The outcome of infection with Salmonella Typhimurium in mouse models of human typhoid fever is dependent upon a coordinated complex immune response. A panel of recombinant congenic strains (RCS) derived from reciprocal backcross of A/J and C57BL/6J mice was screened for their susceptibility to Salmonella infection and two susceptibility loci, Ity4 (Immunity to Typhimurium locus 4) and Ity5, were identified. We validated Ity5 in a genetic environment free of the impact of Ity4 using a cross between A/J and 129S6. Using a time-series analysis of genome-wide transcription during infection, comparing A/J with AcB60 mice having a C57BL/6J-derived Ity5 interval, we have identified the differential expression of the positional candidate gene Cd40, Cd40-associated signaling pathways, and the differential expression of numerous genes expressed in neutrophils. CD40 is known to coordinate T cell-dependent B-cell responses and myeloid cell activation. In fact, CD40 signaling is altered in A/J mice as seen by impaired IgM upregulation during infection, decreased Ig class switching, neutropenia, reduced granulocyte recruitment in response to infection and inflammation, and decreased ERK1/2 activity. These results suggest that altered CD40 signaling and granulocyte recruitment in response to infection are responsible for the Ity5-associated Salmonella susceptibility of A/J mice.

The Role of Pathogenic Autoantibodies in Autoimmunity

The serological presence of autoantibodies is diagnostic of autoimmunity, and these autoantibodies may be present for many years before the presentation of autoimmune disease (AID). Although a pathogenic role has been demonstrated for various autoantibodies reactive with cell surface and extracellular autoantigens, studies using monoclonal antibodies (mAb) show not all antibodies in the polyclonal response are pathogenic. Differences depend on Fab-mediated diversity in epitope specificity, Fc-mediated effects based on immunoglobulin (Ig) class and subclass, activation of complement, and the milieu in which the reaction occurs. These autoantibodies often occur in organ-specific AID and this review illustrates their pathogenic and highly specific effects. The role of autoantibodies associated with intracellular antigens is less clear. In vitro they may inhibit or adversely affect well-defined intracellular biochemical pathways, yet, in vivo they are separated from their autoantigens by multiple cellular barriers. Recent evidence that Ig can traverse cell membranes, interact with intracellular proteins, and induce apoptosis has provided new evidence for a pathogenic role for such autoantibodies. An understanding of how autoantibodies behave in the polyclonal response and their role in pathogenesis of AID may help identify populations of culprit B-cells and selection of treatments that suppress or eliminate them.

Изменение иммунологических показателей вирусной инфекции у пациентов с красным плоским лишаем слизистой оболочки рта

<p>Herpes viruses (cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV) able persist in the body for life and can be reactivated under the influence of various exo- and endogenous trigger factors after primary infection in childhood. Persistent herpes virus infection causes marked clinical immunological changes in a number of somatic and dental diseases. However, the work on the impact of herpes infection on the development and clinical course of oral lichen planus (CPL GRA), in particular, different types of herpes simplex virus (HSV), Epstein-Barr (EB) and cytomegalovirus (CMV) are rare and contradictory. The aim of the work was to determine the immunological parameters of herpesvirus infections in patients with lichen planus of the oral mucosa. The study was performed involving 107 patients with oral lichen planus. A control group comprised 79 healthy people matched for age and sex with the patients of the research team. The examination was performed by enzyme immunoassay (EIA) with determination of antibody Ig classes M and G of HSV and CMV in serum of studied patients. Latent herpes infection found in more than 2/3 of all patients with oral lichen planus, and in patients with severe disease is detected in 2.3 times more likely. Considering that activation and persistence of herpes viruses, regardless of the localization caused them inflammation, promote aggravation immunodeficiency, including the mucous membrane of the mouth, we can assume their role in protracted or chronic course of inflammation with oral lichen planus, possibly including autoimmune mechanisms. This fact must be taken into account in the appointment of an integrated treatment of lichen planus of the oral mucosa.</p>

Development of a Cost-effective Clinical Assay to Simultaneously Screen, Quantitate and Isotype M-proteins in Real-Time Using MALDI-TOF

Background: Current laboratory detection of monoclonal gammopathies includes a panel of serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE) and serum free light chain quantitation (FLC). In this study we sought to evaluate an emerging clinical platform: matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS) as a cost effective, sensitive method to detect, isotype and quantitate M-proteins. Methods: We developed an immuno-enrichment MALDI-TOF MS assay utilizing nanobodies to detect, quantitate and isotype Mproteins. Residual patient serum was enriched for IgG, IgA, IgM, kappa and lambda using nanobodies. After disassociating the heavy or light chains, five separate samples were spotted onto a Bruker Microflex MALDI plate. Automated acquisition (w10 seconds/ sample) was performed and the mass spectra corresponding to light chains from each nanobody were overlaid. M-proteins were detected, quantitated and isotyped by the presence of distinct peaks (mspike) within light chain m/z regions. Results: In M-protein positive patient samples, serial dilution revealed MALDI-TOF MS to have w10-fold lower limit of detection than IFE. Screening concordance for the MALDI-TOF MS was 97.8% for IFE(+) and 100% for SPEP(+) samples. For IFE(-) samples, the concordance was 88.6% with the MALDI-TOF identifying 4 additional positive patients. In samples positive by both methods (N1⁄487), isotyping concordance was 98.9%. The M-Spike quantitation correlation between SPEP and MALDI-TOF was linear with the MALDI giving slightly lower values. The MALDI-TOF method also had good agreement with the Hevy-LiteTM assay for the all three Ig classes. Conclusion: This study demonstrates that detection, quantitation and isotyping of M-proteins by MALDI-TOF MS is robust and exceeds the sensitivity of IFE. Unlike current methods, the MALDI can also document isotype suppression. This method is amendable to automation, is rapid and in its current format is costcompetitive with current clinical isotyping assays.

Complexity of the human memory B-cell compartment is determined by the versatility of clonal diversification in germinal centers

Our knowledge about the clonal composition and intraclonal diversity of the human memory B-cell compartment and the relationship between memory B-cell subsets is still limited, although these are central issues for our understanding of adaptive immunity. We performed a deep sequencing analysis of rearranged immunoglobulin (Ig) heavy chain genes from biological replicates, covering more than 100,000 memory B lymphocytes from two healthy adults. We reveal a highly similar B-cell receptor repertoire among the four main human IgM(+) and IgG(+) memory B-cell subsets. Strikingly, in both donors, 45% of sequences could be assigned to expanded clones, demonstrating that the human memory B-cell compartment is characterized by many, often very large, B-cell clones. Twenty percent of the clones consisted of class switched and IgM(+)(IgD(+)) members, a feature that correlated significantly with clone size. Hence, we provide strong evidence that the vast majority of Ig mutated B cells--including IgM(+)IgD(+)CD27(+) B cells--are post-germinal center (GC) memory B cells. Clone members showed high intraclonal sequence diversity and high intraclonal versatility in Ig class and IgG subclass composition, with particular patterns of memory B-cell clone generation in GC reactions. In conclusion, GC produce amazingly large, complex, and diverse memory B-cell clones, equipping the human immune system with a versatile and highly diverse compartment of IgM(+)(IgD(+)) and class-switched memory B cells.

Nbs1 ChIP-Seq Identifies Off-Target DNA Double-Strand Breaks Induced by AID in Activated Splenic B Cells.

Activation-induced cytidine deaminase (AID) is required for initiation of Ig class switch recombination (CSR) and somatic hypermutation (SHM) of antibody genes during immune responses. AID has also been shown to induce chromosomal translocations, mutations, and DNA double-strand breaks (DSBs) involving non-Ig genes in activated B cells. To determine what makes a DNA site a target for AID-induced DSBs, we identify off-target DSBs induced by AID by performing chromatin immunoprecipitation (ChIP) for Nbs1, a protein that binds DSBs, followed by deep sequencing (ChIP-Seq). We detect and characterize hundreds of off-target AID-dependent DSBs. Two types of tandem repeats are highly enriched within the Nbs1-binding sites: long CA repeats, which can form Z-DNA, and tandem pentamers containing the AID target hotspot WGCW. These tandem repeats are not nearly as enriched at AID-independent DSBs, which we also identified. Msh2, a component of the mismatch repair pathway and important for genome stability, increases off-target DSBs, similar to its effect on Ig switch region DSBs, which are required intermediates during CSR. Most of the off-target DSBs are two-ended, consistent with generation during G1 phase, similar to DSBs in Ig switch regions. However, a minority are one-ended, presumably due to conversion of single-strand breaks to DSBs during replication. One-ended DSBs are repaired by processes involving homologous recombination, including break-induced replication repair, which can lead to genome instability. Off-target DSBs, especially those present during S phase, can lead to chromosomal translocations, deletions and gene amplifications, resulting in the high frequency of B cell lymphomas derived from cells that express or have expressed AID.

Breaking bad: R-loops and genome integrity.

R-loops, nucleic acid structures consisting of an RNA-DNA hybrid and displaced single-stranded (ss) DNA, are ubiquitous in organisms from bacteria to mammals. First described in bacteria where they initiate DNA replication, it now appears that R-loops regulate diverse cellular processes such as gene expression, immunoglobulin (Ig) class switching, and DNA repair. Changes in R-loop regulation induce DNA damage and genome instability, and recently it was shown that R-loops are associated with neurodegenerative disorders. We discuss recent developments in the field; in particular, the regulation and effects of R-loops in cells, their effect on genomic and epigenomic stability, and their potential contribution to the origin of diseases including cancer and neurodegenerative disorders.

Cyclin-dependent kinases regulate Ig class switching by controlling access of AID to the switch region.

Ig class switching requires cell proliferation and is division linked, but the detailed mechanism is unknown. By analyzing the first switching cells early in the kinetics, our analysis suggested that proliferating B cells had a very short G1 phase (<3.5 h), a total cell cycle time of ∼ 11 h, and that Ig class switching preferentially occurred in the late G1 or early S phase. Inhibition of cyclin-dependent kinases (CDKs) caused dramatic reduction of switching rate within 6 h. This was associated with less targeting of activation-induced cytidine deaminase (AID) to the Igh locus. Interestingly, ectopically expressed nuclear AID in HeLa cells was preferentially found in the early S phase. Furthermore, in CDK2 hypomorphic cells there was reduced nuclear AID accumulation. Thus, our data are compatible with the idea that division-linked Ig class switching is in part due to CDK2-regulated AID nuclear access at the G1/S border.

Significance of IL-15 in IL-4 induced B cell activation, immunoglobulin isotype class switching and IgE production (IRM10P.613)

Abstract IgE-mediated immune responses contribute to the pathogenesis of allergic diseases. Despite their significant role in immune biology, the factors that produce and regulate IgE responses are yet to be established. Notably, IL-4 is a well-established cytokine involved in immunoglobulin (Ig) isotype class switching and IgE production. However we recently observed that IL-15 over expression in mice (pharmacologically or by transgene insertion) induces IgE levels. Therefore we hypothesized that IL-15 might have some role in B cells proliferation, activation, Ig isotype class switching and IgE production. Accordingly we examined the level of IgE, B cells and Ig isotype class switching in response to IL-15 using ELISA, real time qPCR and flowcytometric analysis. Our initial in vitro data show proliferation, activation and induced Ig class switching genes in purified B cells following rIL-15 treatments. Further, we show reduced IgE levels in IL-15 gene-deficient mice compared to Balbc mice following Aspergillus fumigatus exposure. Furthermore we examined the role of IL-15 in IL-4 mediated IgE production. We observed that IL-4 gene-deficient mice have increased IgE levels and B cell activation following intravenous administration of IL-15 compared to saline. However, significant IgE levels were observed following IL-15 treatment in Balbc mice compared to IL-4 gene-deficient mice.Together we conclude that IL-15 is required for the IL-4 induced B cell activation and allergen induced IgE.

Constraints contributed by chromatin looping limit recombination targeting during Ig class switch recombination.

Engagement of promoters with distal elements in long-range looping interactions has been implicated in regulation of Ig class switch recombination (CSR). The principles determining the spatial and regulatory relationships among Igh transcriptional elements remain poorly defined. We examined the chromosome conformation of C region (CH) loci that are targeted for CSR in a cytokine-dependent fashion in mature B lymphocytes. Germline transcription (GLT) of the γ1 and ε CH loci is controlled by two transcription factors, IL-4-inducible STAT6 and LPS-activated NF-κB. We showed that although STAT6 deficiency triggered loss of GLT, deletion of NF-κB p50 abolished both GLT and γ1 locus:enhancer looping. Thus, chromatin looping between CH loci and Igh enhancers is independent of GLT production and STAT6, whereas the establishment and maintenance of these chromatin contacts requires NF-κB p50. Comparative analysis of the endogenous γ1 locus and a knock-in heterologous promoter in mice identified the promoter per se as the interactive looping element and showed that transcription elongation is dispensable for promoter/enhancer interactions. Interposition of the LPS-responsive heterologous promoter between the LPS-inducible γ3 and γ2b loci altered GLT expression and essentially abolished direct IgG2b switching while maintaining a sequential μ→γ3→γ2b format. Our study provides evidence that promoter/enhancer looping interactions can introduce negative constraints on distal promoters and affect their ability to engage in germline transcription and determine CSR targeting.

Serum thyroid hormone autoantibodies in type 1 diabetes mellitus.

Autoimmune thyroid diseases (AITDs) can be associated with type 1 diabetes (DM1). The prevalence of serum antibodies against thyroid hormones (THAb) in subjects with autoimmune diseases other than DM1 is increasing. No data are available for DM1. The objectives were evaluate the rate of associated AITD; the rate of positiveness for serum THAb; the panel of THAb based on thyroid hormone interaction and on Ig class; and the association of AITD alone, THAb alone, or AITD plus THAb with diabetes-related complications. This was an observational, prospective study with 6-year (2005-2011) follow-up. The setting was an outpatient diabetes clinic. Fifty-two consecutive subjects (53.8% males; mean age, 37.4 ± 7.4 y; diabetes duration, 19.9 ± 8.2 y) with DM1. All participants completed the study. Main outcome measures were AITD rate; THAb positivity according to hormone interaction and Ig class; association of AITD and THAb with diabetes-related complications. AITD rate increased from baseline (34.6%) to follow-up (38.5%). Subjects with DM1 had a high prevalence of THAb (92.3%). The presence of AITD at baseline was associated with subsequent development of macroangiopathy (0 vs 33% at baseline and follow-up, respectively; P = .029). Some THAb patterns, the majority having T3 binding in common, were associated with the progression and development of diabetes-related complications. THAb synthesis in DM1 might be driven by increased glycosylation of thyroglobulin. Anti T3-THAb may cause a relative "tissue hypothyroidism" by sequestering thyroid hormone, this at least partially contributing to worsening diabetes-related vascular complications. In a clinical setting THAb positivity could identify subjects more likely to develop diabetes complications.

Self-Restrained B Cells Arise following Membrane IgE Expression

Among immunoglobulins (Igs), IgE can powerfully contribute to antimicrobial immunity and severe allergy despite its low abundance. IgE protein and gene structure resemble other Ig classes, making it unclear what constrains its production to thousand-fold lower levels. Whether class-switched B cell receptors (BCRs) differentially control B cell fate is debated, and study of the membrane (m)IgE class is hampered by its elusive invivo expression. Here, we demonstrate a self-controlled mIgE+ B cell stage. Primary or transfected mIgE+ cells relocate the BCRs into spontaneously internalized lipid rafts, lose mobility to chemokines, and change morphology. We suggest that combined proapoptotic mechanisms possibly involving Hax1 prevent mIgE+ memory lymphocyte accumulation. By uncoupling invivo IgE switching from cytokine and antigen stimuli, we show that these features are independent from B cell stimulation and instead result from mIgE expression per se. Consequently, few cells survive IgE class switching, which might ensure minimal long-term IgE memory upon differentiation into plasma cells.

Immunoglobulin G kappa biclonal gammopathy associated with multiple myeloma, plasmacytoma and cast nephropathy

Biclonal gammopathies are characterized by simultaneous appearance of two different monoclonal proteins. Multiclonal gammopathies may be the result of a neoplastic transformation of a cell clone undergoing immunoglobulin (Ig) class switching or due to an independent neoplastic transformation event yielding proliferation of unrelated plasma cell clones. This in turn has implication on the disease manifestation, progression, prognosis and response to therapy. The prevalence of biclonal gammopathy is approximately 1% of all gammopathies and the most common combinations are IgG and IgA (33%), followed by IgM and IgG (24%). Multiple myeloma with biclonal gammopathy is very uncommon. The present case corresponds to an extremely rare occurrence of multiple myeloma with biclonal gammopathy revealing expression of two distinct monoclonal gammaglobulins both of IgG and kappa (κ) subtype in a 56-year-old diabetic man who presented with lower back pain and renal failure. To the best of our knowledge, only one case of IgG κ biclonal gammopathy associated with multiple myeloma have been reported in English literature. This case interestingly also had paraspinal plasmacytoma and cast nephropathy.