scholarly journals Sequential activation and distinct functions for distal and proximal modules within the IgH 3′ regulatory region

2016 ◽  
Vol 113 (6) ◽  
pp. 1618-1623 ◽  
Author(s):  
Armand Garot ◽  
Marie Marquet ◽  
Alexis Saintamand ◽  
Sébastien Bender ◽  
Sandrine Le Noir ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Somatic Hypermutation ◽  
Regulatory Region ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Receptor Expression ◽  
Class Switch ◽  
Cell Ontogeny

As a master regulator of functional Ig heavy chain (IgH) expression, the IgH 3′ regulatory region (3′RR) controls multiple transcription events at various stages of B-cell ontogeny, from newly formed B cells until the ultimate plasma cell stage. The IgH 3′RR plays a pivotal role in early B-cell receptor expression, germ-line transcription preceding class switch recombination, interactions between targeted switch (S) regions, variable region transcription before somatic hypermutation, and antibody heavy chain production, but the functional ranking of its different elements is still inaccurate, especially that of its evolutionarily conserved quasi-palindromic structure. By comparing relevant previous knockout (KO) mouse models (3′RR KO and hs3b-4 KO) to a novel mutant devoid of the 3′RR quasi-palindromic region (3′PAL KO), we pinpointed common features and differences that specify two distinct regulatory entities acting sequentially during B-cell ontogeny. Independently of exogenous antigens, the 3′RR distal part, including hs4, fine-tuned B-cell receptor expression in newly formed and naïve B-cell subsets. At mature stages, the 3′RR portion including the quasi-palindrome dictated antigen-dependent locus remodeling (global somatic hypermutation and class switch recombination to major isotypes) in activated B cells and antibody production in plasma cells.

scholarly journals Characterization of B-cell Receptor Heavy Chain Complementarity-determining Region 3 Repertoire Based on the Differences of Symbiotic Microorganisms in the Gut of Mice

2021 ◽  
Author(s):  
Jun Li ◽  
Yurong Pan ◽  
Qingqing Ma ◽  
Long Ma ◽  
Bin Shi ◽  
...  
Keyword(s):  
Small Intestine ◽  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Intestinal Microflora ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Positive Effects ◽  
Significant Difference

Abstract Background Colonization of gut microorganism is related to maturation of B cells in peripheral immune organs. This study aims to investigate the effect of intestinal microflora in Germ-free (GF), Specific Pathogen-free (SPF) and Clean (CL) BALB/C mice to small intestine total B-cell and memory B-cell receptor (BCR) complementary-determining region 3 (CDR3) repertoire. Results The composition and characteristics of intestinal microflora were analyzed by 16S rDNA sequencing. Genomic DNA extracted from small intestine tissue and memory B-cells of GF, SPF and CL mice were conducted via high-throughput DNA sequencing methods. As expected, significant differences of gut microflora diversity were observed in the three mice groups. CL group showed the most diversity, followed by SPF group, and GF group had the lowest diversity. Moreover, anormogenesis of intestinal lymphoid tissue were observed in GF mice. Diversity of the BCR heavy chain CDR3 repertoire in memory B cells were significant difference among three groups, but not in total B cells. The nucleotide polymorphism, usage frequency of gene segments (V, D, J, V–J gene segments) and amino acid of total B cells and memory B cells CDR3 were comparable among three mice groups, and there was significant difference between CL and GF mice groups. Conclusions The results of this study advocate that the colonization of intestinal microorganisms affect the diversity of B cells CDR3 repertoire. Elucidating mechanism of microbiome participated in the function of intestinal mucosal immune system may have positive effects on human health, and it requires further investigation.

scholarly journals Signatures of B Cell Receptor Repertoire Following Pneumocystis Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Han Sun ◽  
Hu-Qin Yang ◽  
Kan Zhai ◽  
Zhao-Hui Tong
Keyword(s):  
B Cells ◽  
B Cell ◽  
Single Cell ◽  
Plasma Cells ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Receptor Repertoire ◽  
Elevated Expression ◽  
Pneumocystis Infection

B cells play vital roles in host defense against Pneumocystis infection. However, the features of the B cell receptor (BCR) repertoire in disease progression remain unclear. Here, we integrated single-cell RNA sequencing and single-cell BCR sequencing of immune cells from mouse lungs in an uninfected state and 1–4 weeks post-infection in order to illustrate the dynamic nature of B cell responses during Pneumocystis infection. We identified continuously increased plasma cells and an elevated ratio of (IgA + IgG) to (IgD + IgM) after infection. Moreover, Pneumocystis infection was associated with an increasing naïve B subset characterized by elevated expression of the transcription factor ATF3. The proportion of clonal expanded cells progressively increased, while BCR diversity decreased. Plasma cells exhibited higher levels of somatic hypermutation than naïve B cells. Biased usage of V(D)J genes was observed, and the usage frequency of IGHV9-3 rose. Overall, these results present a detailed atlas of B cell transcriptional changes and BCR repertoire features in the context of Pneumocystis infection, which provides valuable information for finding diagnostic biomarkers and developing potential immunotherapeutic targets.

An Alternatively Spliced Form of CD79b Gene May Account for Altered B-Cell Receptor Expression in B-Chronic Lymphocytic Leukemia

Blood ◽  
1999 ◽  
Vol 93 (7) ◽  
pp. 2327-2335 ◽  
Author(s):  
A. Alfarano ◽  
S. Indraccolo ◽  
P. Circosta ◽  
S. Minuzzo ◽  
A. Vallario ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Cell Lines ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Receptor Expression ◽  
Rt Pcr ◽  
Alternatively Spliced

Several functional anomalies of B-chronic lymphocytic leukemia (B-CLL) cells may be explained by abnormalities of the B-cell receptor (BCR), a multimeric complex formed by the sIg homodimer and the noncovalently bound heterodimer Ig/Igβ (CD79a/CD79b). Because the expression of the extracellular Ig-like domain of CD79b has been reported to be absent in the cells of most CLL cases, we have investigated the molecular mechanisms that may account for this defect. Peripheral blood lymphocytes (PBL) from 50 patients and two cell lines (MEC1, MEC2) obtained from the PBL of one of them were studied. MEC1, MEC2, and 75% of CLL cases did not express detectable levels of the extracellular Ig-like domain of CD79b, which was nevertheless present in greater than 80% CD19+ cells from normal donors. In healthy subjects the expression of CD79b was equally distributed in CD5+ and CD5− B-cell subsets. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of CD79b RNA from all patients and from MEC1 and MEC2 cell lines consistently yielded two fragments of different size (709 bp and 397 bp). The 709-bp band corresponds to CD79b entire transcript; the 397-bp band corresponds to an alternatively spliced form lacking exon 3 that encodes the extracellular Ig-like domain. Both fragments were also visible in normal PBL. The expression of the 397-bp fragment was increased in normal activated B cells, while no difference was seen between CD5+ and CD5− B cells. To obtain a more accurate estimate of the relative proportions of the two spliced forms, a radioactive PCR was performed in 13 normal and 22 B-CLL samples and the results analyzed using a digital imager. The mean value of the CD79b to the CD79b internally deleted ratio was 0.64 ± 0.20 SD in normal donors and 0.44 ± 0.27 SD in B-CLL (P = .01). Direct sequencing of 397-bp RT-PCR products and of genomic DNA corresponding to exon 3 from MEC1, MEC2, their parental cells, and five fresh B-CLL samples did not show any causal mutation. Single-strand conformation polymorphism analysis of exon 3 performed in 18 additional B-CLL cases showed a single abnormal shift corresponding to a TGT → TGC polymorphic change at amino acid 122. We propose a role for the alternative splicing of CD79b gene in causing the reduced expression of BCR on the surface of B-CLL cells. As normal B cells also present this variant, the mechanism of CD79b posttranscriptional regulation might reflect the activation stage of the normal B cell from which B-CLL derives.

scholarly journals B Lymphocyte Chemotaxis Regulated in Association with Microanatomic Localization, Differentiation State, and B Cell Receptor Engagement

1998 ◽  
Vol 187 (5) ◽  
pp. 753-762 ◽  
Author(s):  
Conrad C. Bleul ◽  
Joachim L. Schultze ◽  
Timothy A. Springer
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocytes ◽  
Messenger Rna ◽  
B Lymphocyte ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Cxc Chemokine

Migration of mature B lymphocytes within secondary lymphoid organs and recirculation between these sites are thought to allow B cells to obtain T cell help, to undergo somatic hypermutation, to differentiate into effector cells, and to home to sites of antibody production. The mechanisms that direct migration of B lymphocytes are unknown, but there is evidence that G protein–coupled receptors, and possibly chemokine receptors, may be involved. Stromal cell– derived factor (SDF)-1α is a CXC chemokine previously characterized as an efficacious chemoattractant for T lymphocytes and monocytes in peripheral blood. Here we show with purified tonsillar B cells that SDF-1α also attracts naive and memory, but not germinal center (GC) B lymphocytes. Furthermore, GC B cells could be converted to respond to SDF-1α by in vitro differentiation into memory B lymphocytes. Conversely, the migratory response in naive and memory B cells was significantly reduced after B cell receptor engagement and CD40 signaling. The receptor for SDF-1, CXC chemokine receptor 4 (CXCR4), was found to be expressed on responsive as well as unresponsive B cell subsets, but was more rapidly downregulated on responsive cells by ligand. Finally, messenger RNA for SDF-1 was detected by in situ hybridization in a layer of cells surrounding the GC. These findings show that responsiveness to the chemoattractant SDF-1α is regulated during B lymphocyte activation, and correlates with positioning of B lymphocytes within a secondary lymphoid organ.

The immunoglobulin heavy-chain locus hs3b and hs4 3′ enhancers are dispensable for VDJ assembly and somatic hypermutation

Blood ◽  
2003 ◽  
Vol 102 (4) ◽  
pp. 1421-1427 ◽  
Author(s):  
Caroline Le Morvan ◽  
Eric Pinaud ◽  
Catherine Decourt ◽  
Armelle Cuvillier ◽  
Michel Cogné
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Immunoglobulin Heavy Chain ◽  
Germinal Centers ◽  
Affinity Maturation ◽  
Class Switch ◽  
Endogenous Locus

Abstract The more distal enhancers of the immunoglobulin heavy-chain 3′ regulatory region, hs3b and hs4, were recently demonstrated as master control elements of germline transcription and class switch recombination to most immunoglobulin constant genes. In addition, they were shown to enhance the accumulation of somatic mutations on linked transgenes. Since somatic hypermutation and class switch recombination are tightly linked processes, their common dependency on the endogenous locus 3′ enhancers could be an attractive hypothesis. VDJ structure and somatic hypermutation were analyzed in B cells from mice carrying either a heterozygous or a homozygous deletion of these enhancers. We find that hs3b and hs4 are dispensable both for VDJ assembly and for the occurrence of mutations at a physiologic frequency in the endogenous locus. In addition, we show that cells functionally expressing the immunoglobulin M (IgM) class B-cell receptor encoded by an hs3b/hs4-deficient locus were fully able to enter germinal centers, undergo affinity maturation, and yield specific antibody responses in homozygous mutant mice, where IgG1 antibodies compensated for the defect in other IgG isotypes. By contrast, analysis of Peyer patches from heterozygous animals showed that peanut agglutinin (PNAhigh) B cells functionally expressing the hs3b/hs4-deficient allele were dramatically outclassed by B cells expressing the wild-type locus and normally switching to IgA. This study thus also highlights the role of germinal centers in the competition between B cells for affinity maturation and suggests that membrane IgA may promote recruitment in an activated B-cell compartment, or proliferation of activated B cells, more efficiently than IgM in Peyer patches.

scholarly journals Antibody Repertoire Analysis of Tumor-Infiltrating B Cells Reveals Distinct Signatures and Distributions Across Tissues

2021 ◽  
Vol 12 ◽  
Author(s):  
Ligal Aizik ◽  
Yael Dror ◽  
David Taussig ◽  
Adi Barzel ◽  
Yaron Carmi ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
High Throughput Sequencing ◽  
Triple Negative ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
Antibody Repertoire ◽  
Class Switch ◽  
Repertoire Analysis

The role of B cells in the tumor microenvironment (TME) has largely been under investigated, and data regarding the antibody repertoire encoded by B cells in the TME and the adjacent lymphoid organs are scarce. Here, we utilized B cell receptor high-throughput sequencing (BCR-Seq) to profile the antibody repertoire signature of tumor-infiltrating lymphocyte B cells (TIL−Bs) in comparison to B cells from three anatomic compartments in a mouse model of triple-negative breast cancer. We found that TIL-Bs exhibit distinct antibody repertoire measures, including high clonal polarization and elevated somatic hypermutation rates, suggesting a local antigen-driven B-cell response. Importantly, TIL-Bs were highly mutated but non-class switched, suggesting that class-switch recombination may be inhibited in the TME. Tracing the distribution of TIL-B clones across various compartments indicated that they migrate to and from the TME. The data thus suggests that antibody repertoire signatures can serve as indicators for identifying tumor-reactive B cells.

scholarly journals One-step generation of monoclonal B cell receptor mice capable of class switch recombination and somatic hypermutation

2017 ◽  
Author(s):  
Johanne T. Jacobsen ◽  
Luka Mesin ◽  
Styliani Markoulaki ◽  
Cecília B. Cavazzoni ◽  
Djenet Bousbaine ◽  
...  
Keyword(s):  
B Cell ◽  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Cell Receptor ◽  
Affinity Maturation ◽  
B Cell Receptor ◽  
Class Switch ◽  
One Step ◽  
Step Generation ◽  
Rapid Generation

We developed a method for rapid generation of B cell receptor (BCR) monoclonal mice expressing pre-rearranged Igh and Igk chains monoallelically from the Igh locus by CRISPR/Cas9 injection into fertilized oocytes. B cells from these mice undergo somatic hypermutation (SHM), class switch recombination (CSR), and affinity-based selection in germinal centers. This method combines the practicality of BCR transgenes with the ability to study Ig SHM, CSR and affinity maturation.

scholarly journals Malaria-associated atypical memory B cells exhibit markedly reduced B cell receptor signaling and effector function

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Silvia Portugal ◽  
Christopher M Tipton ◽  
Haewon Sohn ◽  
Younoussou Kone ◽  
Jing Wang ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Viral Infections ◽  
Somatic Hypermutation ◽  
Plasmodium Falciparum Malaria ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Chronic Infections ◽  
Malaria Exposure

Protective antibodies in Plasmodium falciparum malaria are only acquired after years of repeated infections. Chronic malaria exposure is associated with a large increase in atypical memory B cells (MBCs) that resemble B cells expanded in a variety of persistent viral infections. Understanding the function of atypical MBCs and their relationship to classical MBCs will be critical to developing effective vaccines for malaria and other chronic infections. We show that VH gene repertoires and somatic hypermutation rates of atypical and classical MBCs are indistinguishable indicating a common developmental history. Atypical MBCs express an array of inhibitory receptors and B cell receptor (BCR) signaling is stunted in atypical MBCs resulting in impaired B cell responses including proliferation, cytokine production and antibody secretion. Thus, in response to chronic malaria exposure, atypical MBCs appear to differentiate from classical MBCs becoming refractory to BCR-mediated activation and potentially interfering with the acquisition of malaria immunity.

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