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Class switch recombination

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https://www.readbyqxmd.com/read/28215280/molecular-mechanisms-of-somatic-hypermutation-and-class-switch-recombination
#1
S P Methot, J M Di Noia
In order to promote an efficient humoral immune response, germinal center B cells modify both the antigen recognition and effector domains by programmed genetic alterations of their antibody genes. To do so, B cells use the enzyme activation-induced deaminase (AID), which transforms deoxycytidine into deoxyuridine at the immunoglobulin genes, triggering mutagenic DNA repair. Data accumulated during the past decade have significantly advanced our understanding of how AID activity is regulated and preferentially targeted to the immunoglobulin genes...
2017: Advances in Immunology
https://www.readbyqxmd.com/read/28199309/phosphatidylinositol-3-kinase-%C3%AE-blockade-increases-genomic-instability-in-b-cells
#2
Mara Compagno, Qi Wang, Chiara Pighi, Taek-Chin Cheong, Fei-Long Meng, Teresa Poggio, Leng-Siew Yeap, Elif Karaca, Rafael B Blasco, Fernanda Langellotto, Chiara Ambrogio, Claudia Voena, Adrian Wiestner, Siddha N Kasar, Jennifer R Brown, Jing Sun, Catherine J Wu, Monica Gostissa, Frederick W Alt, Roberto Chiarle
Activation-induced cytidine deaminase (AID) is a B-cell-specific enzyme that targets immunoglobulin genes to initiate class switch recombination and somatic hypermutation. In addition, through off-target activity, AID has a much broader effect on genomic instability by initiating oncogenic chromosomal translocations and mutations involved in the development and progression of lymphoma. AID expression is tightly regulated in B cells and its overexpression leads to enhanced genomic instability and lymphoma formation...
February 15, 2017: Nature
https://www.readbyqxmd.com/read/28188246/cutting-edge-the-transcription-factor-sox2-regulates-aid-expression-in-class-switched-b-cells
#3
Lauren J DiMenna, Wei-Feng Yen, Laura Nicolas, Rahul Sharma, Zara N Saldanha, Jayanta Chaudhuri
IgH class switch recombination (CSR) occurs through the deliberate introduction of activation-induced cytidine deaminase (AID)-instigated DNA double-strand breaks into the IgH loci. Because double-strand breaks are generally highly toxic, mechanisms that regulate AID expression are of much relevance to CSR and genomic integrity; however, effectors of such regulatory processes are still poorly understood. In this article, we show that the transcription factor sex determining region Y-box 2 (Sox2) is expressed in activated B cells, but almost exclusively in those that have undergone CSR...
February 10, 2017: Journal of Immunology: Official Journal of the American Association of Immunologists
https://www.readbyqxmd.com/read/28176781/rad52-competes-with-ku70-ku86-for-binding-to-s-region-dsb-ends-to-modulate-antibody-class-switch-dna-recombination
#4
Hong Zan, Connie Tat, Zhifang Qiu, Julia R Taylor, Justin A Guerrero, Tian Shen, Paolo Casali
Antibody class-switch DNA recombination (CSR) is initiated by AID-introduced DSBs in the switch (S) regions targeted for recombination, as effected by Ku70/Ku86-mediated NHEJ. Ku-deficient B cells, however, undergo (reduced) CSR through an alternative(A)-NHEJ pathway, which introduces microhomologies in S-S junctions. As microhomology-mediated end-joining requires annealing of single-strand DNA ends, we addressed the contribution of single-strand annealing factors HR Rad52 and translesion DNA polymerase θ to CSR...
February 8, 2017: Nature Communications
https://www.readbyqxmd.com/read/28159901/53bp1-contributes-to-igh-locus-chromatin-topology-during-class-switch-recombination
#5
Scott Feldman, Robert Wuerffel, Ikbel Achour, Lili Wang, Phillip B Carpenter, Amy L Kenter
In B lymphocytes, Ig class switch recombination (CSR) is induced by activation-induced cytidine deaminase, which initiates a cascade of events leading to DNA double-strand break formation in switch (S) regions. Resolution of DNA double-strand breaks proceeds through formation of S-S synaptic complexes. S-S synapsis is mediated by a chromatin loop that spans the C region domain of the Igh locus. S-S junctions are joined via a nonhomologous end joining DNA repair process. CSR occurs via an intrachromosomal looping out and deletion mechanism that is 53BP1 dependent...
February 3, 2017: Journal of Immunology: Official Journal of the American Association of Immunologists
https://www.readbyqxmd.com/read/28137874/igd-class-switching-is-initiated-by-microbiota-and-limited-to-mucosa-associated-lymphoid-tissue-in-mice
#6
Jin Huk Choi, Kuan-Wen Wang, Duanwu Zhang, Xiaowei Zhan, Tao Wang, Chun-Hui Bu, Cassie L Behrendt, Ming Zeng, Ying Wang, Takuma Misawa, Xiaohong Li, Miao Tang, Xiaoming Zhan, Lindsay Scott, Sara Hildebrand, Anne R Murray, Eva Marie Y Moresco, Lora V Hooper, Bruce Beutler
Class-switch recombination (CSR) alters the Ig isotype to diversify antibody effector functions. IgD CSR is a rare event, and its regulation is poorly understood. We report that deficiency of 53BP1, a DNA damage-response protein, caused age-dependent overproduction of secreted IgD resulting from increased IgD CSR exclusively within B cells of mucosa-associated lymphoid tissues. IgD overproduction was dependent on activation-induced cytidine deaminase, hematopoietic MyD88 expression, and an intact microbiome, against which circulating IgD, but not IgM, was reactive...
January 30, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28125732/dysregulation-of-systemic-and-mucosal-humoral-responses-to-microbial-and-food-antigens-as-a-factor-contributing-to-microbial-translocation-and-chronic-inflammation-in-hiv-1-infection
#7
Zdenek Hel, Jun Xu, Warren L Denning, E Scott Helton, Richard P H Huijbregts, Sonya L Heath, E Turner Overton, Benjamin S Christmann, Charles O Elson, Paul A Goepfert, Jiri Mestecky
HIV-1 infection is associated with an early and profound depletion of mucosal memory CD4+ T cells, a population that plays an indispensable role in the regulation of isotype switching and transepithelial transport of antibodies. In this study, we addressed whether the depletion of CD4+ T cell in HIV-1-infected individuals results in altered humoral responses specific to antigens encountered at mucosal surfaces. Comprehensive protein microarray of systemic humoral responses to intestinal microbiota demonstrated reduced IgG responses to antigens derived from Proteobacteria and Firmicutes but not Bacteroidetes...
January 2017: PLoS Pathogens
https://www.readbyqxmd.com/read/28105679/robust-immunoglobulin-class-switch-recombination-and-end-joining-in-parp9-deficient-mice
#8
Isabelle Robert, Léa Gaudot, Jose Yelamos, Aurélia Noll, Heng-Kuan Wong, Françoise Dantzer, Valérie Schreiber, Bernardo Reina-San-Martin
To mount highly specific and adapted immune responses, B lymphocytes assemble and diversify their antibody repertoire through mechanisms involving the formation of programmed DNA damage. Immunoglobulin class switch recombination (CSR) is triggered by DNA lesions induced by activation-induced cytidine deaminase, which are processed to double-stranded DNA break (DSB) intermediates. These DSBs activate the cellular DNA damage response and enroll numerous DNA repair factors, involving Poly(ADP-ribose) polymerases Parp1, Parp2 and Parp3 to promote appropriate DNA repair and efficient long-range recombination...
January 20, 2017: European Journal of Immunology
https://www.readbyqxmd.com/read/28104464/genetic-defects-in-pi3k%C3%AE-affect-b-cell-differentiation-and-maturation-leading-to-hypogammaglobulineamia-and-recurrent-infections
#9
Marjolein Wentink, Virgil Dalm, Arjan C Lankester, Pauline A van Schouwenburg, Liesbeth Schölvinck, Tomas Kalina, Radana Zachova, Anna Sediva, Annechien Lambeck, Ingrid Pico-Knijnenburg, Jacques J M van Dongen, Malgorzata Pac, Ewa Bernatowska, Martin van Hagen, Gertjan Driessen, Mirjam van der Burg
BACKGROUND: Mutations in PIK3CD and PIK3R1 cause activated PI3K-δ syndrome (APDS) by dysregulation of the PI3K-AKT pathway. METHODS: We studied precursor and peripheral B-cell differentiation and apoptosis via flowcytometry. Furthermore, we performed AKT-phosphorylation assays and somatic hypermutations (SHM) and class switch recombination (CSR) analysis. RESULTS: We identified 13 patients of whom 3 had new mutations in PIK3CD or PIK3R1. Patients had low total B-cell numbers with increased frequencies of transitional B cells and plasmablasts, while the precursor B-cell compartment in bone marrow was relatively normal...
January 17, 2017: Clinical Immunology: the Official Journal of the Clinical Immunology Society
https://www.readbyqxmd.com/read/28088785/the-igh-locus-3-cis-regulatory-super-enhancer-co-opts-aid-for-allelic-transvection
#10
Sandrine Le Noir, Brice Laffleur, Claire Carrion, Armand Garot, Sandrine Lecardeur, Eric Pinaud, Yves Denizot, Jane Skok, Michel Cogné
Immunoglobulin heavy chain (IgH) alleles have ambivalent relationships: they feature both allelic exclusion, ensuring monoallelic expression of a single immunoglobulin (Ig) allele, and frequent inter-allelic class-switch recombination (CSR) reassembling genes from both alleles. The IgH locus 3' regulatory region (3'RR) includes several transcriptional cis-enhancers promoting activation-induced cytidine deaminase (AID)-dependent somatic hypermutation (SHM) and CSR, and altogether behaves as a strong super-enhancer...
January 10, 2017: Oncotarget
https://www.readbyqxmd.com/read/28073404/isolation-and-characterization-of-hiv-1-envelope-glycoprotein-specific-b-cell-from-immortalized-human-na%C3%A3-ve-b-cell-library
#11
Zehua Sun, Shiqiang Lu, Zheng Yang, Jingjing Li, Meiyun Zhang
With the recent development of single B cell cloning techniques, an increasing number of HIV-1-specific broadly neutralizing antibodies (bNAbs) have been isolated since 2009. However, knowledge regarding HIV-1-specific B cells in vivo is limited. In this study, an HIV-1-specific B cell line has been established using healthy PBMC donors by the highly efficient EBV transformation method to generate immortalized human naïve B cell libraries. The enrichment of HIV-1 envelope-specific B cells was observed after four rounds of cell panning with the HIV-1 envelope glycoprotein...
January 10, 2017: Journal of General Virology
https://www.readbyqxmd.com/read/28069372/rna-exosome-and-non-coding-rna-coupled-mechanisms-in-aid-mediated-genomic-alterations
#12
REVIEW
Brice Laffleur, Uttiya Basu, Junghyun Lim
The eukaryotic RNA exosome is a well-conserved protein complex with ribonuclease activity implicated in RNA metabolism. Various families of non-coding RNAs have been identified as substrates of the complex, underscoring its role as a non-coding RNA processing/degradation unit. However, the role of RNA exosome and its RNA processing activity on DNA mutagenesis/alteration events have not been investigated until recently. B lymphocytes use two DNA alteration mechanisms, class switch recombination (CSR) and somatic hypermutation (SHM), to re-engineer their antibody gene expressing loci until a tailored antibody gene for a specific antigen is satisfactorily generated...
January 7, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28065739/r-loop-depletion-by-over-expressed-rnase-h1-in-mouse-b-cells-increases-activation-induced-deaminase-access-to-the-transcribed-strand-without-altering-frequency-of-isotype-switching
#13
Robert W Maul, Hyongi Chon, Kiran Sakhuja, Susana M Cerritelli, Lina A Gugliotti, Patricia J Gearhart, Robert J Crouch
R-loops, three-strand structures consisting of mRNA hybridized to the complementary DNA and a single-stranded DNA loop, are formed in switch regions on the heavy-chain immunoglobulin locus. To determine if R-loops have a direct effect on any of the steps involved in isotype switching, we generated a transgenic mouse that over-expressed RNase H1, an enzyme that cleaves the RNA of RNA/DNA hybrids in B cells. R-loops in the switch μ region were depleted by 70% in ex vivo activated splenic B cells. Frequencies of isotype switching to IgG1, IgG2b, IgG2c, and IgG3 were the same as C57BL/6 control cells...
January 6, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28058717/deletional-tolerance-prevents-aqp4-directed-autoimmunity-in-mice
#14
Anna-Lena Vogel, Benjamin Knier, Katja Lammens, Sudhakar Reddy Kalluri, Tanja Kuhlmann, Jeffrey L Bennett, Thomas Korn
Neuromyelitis optica (NMO) is an autoimmune disorder of the central nervous system (CNS) mediated by antibodies to the water channel protein AQP4 expressed in astrocytes. The contribution of AQP4-specific T cells to the class switch recombination of pathogenic AQP4-specific antibodies and the inflammation of the blood-brain barrier is incompletely understood, as immunogenic naturally processed T-cell epitopes of AQP4 are unknown. By immunizing Aqp4(-/-) mice with full-length murine AQP4 protein followed by recall with overlapping peptides, we here identify AQP4(201-220) as the major immunogenic IA(b) -restricted epitope of AQP4...
January 5, 2017: European Journal of Immunology
https://www.readbyqxmd.com/read/28012163/il-10-production-in-murine-igm-cd138-hi-cells-is-driven-by-blimp1-and-downregulated-in-class-switched-cells
#15
Nao Suzuki-Yamazaki, Rieko Yanobu-Takanashi, Tadashi Okamura, Satoshi Takaki
In contrast to antibody-induced inflammatory responses, some B-cell subpopulations suppress inflammation through the production of interleukin (IL)-10. However, the mechanisms underlying Il10 gene expression during B-cell development is elusive. Here, we identify IgM(+) B220(lo) CD138(hi) cells responsible for marked IL-10 production in the bone marrow and spleen of mice. These murine IL-10-producing cells predominantly secrete IgM and have unique characteristics of long-lived plasma cells in spite of high expression of surface IgM...
December 23, 2016: European Journal of Immunology
https://www.readbyqxmd.com/read/28011866/the-aryl-hydrocarbon-receptor-controls-cell-fate-decisions-in-b-cells
#16
Bharat Vaidyanathan, Ashutosh Chaudhry, William T Yewdell, Davide Angeletti, Wei-Feng Yen, Adam K Wheatley, Christopher A Bradfield, Adrian B McDermott, Jonathan W Yewdell, Alexander Y Rudensky, Jayanta Chaudhuri
Generation of cellular heterogeneity is an essential feature of the adaptive immune system. This is best exemplified during humoral immune response when an expanding B cell clone assumes multiple cell fates, including class-switched B cells, antibody-secreting plasma cells, and memory B cells. Although each cell type is essential for immunity, their generation must be exquisitely controlled because a class-switched B cell cannot revert back to the parent isotype, and a terminally differentiated plasma cell cannot contribute to the memory pool...
January 2017: Journal of Experimental Medicine
https://www.readbyqxmd.com/read/28000955/chronic-airway-inflammation-provides-a-unique-environment-for-b-cell-activation-and-antibody-production
#17
Scott Feldman, Richard Kasjanski, Julie Popowski, David Hernandez, Jason Chen, James E Norton, Lydia Suh, Roderick G Carter, Whitney W Stevens, Anju T Peters, Robert C Kern, David B Conley, Bruce K Tan, Stephani Shintani-Smith, Kevin C Welch, Leslie C Grammer, Kathleen E Harris, Atsushi Kato, Robert P Schleimer, Kathryn E Hulse
BACKGROUND: B cells play many roles in health and disease. However, little is known about the mechanisms that drive B cell responses in the airways, especially in humans. Chronic rhinosinusitis (CRS) is an inflammatory disease of the upper airways that affects 10% of Europeans and Americans. A subset of CRS patients develop nasal polyps (NP), which are characterized by type 2 inflammation, eosinophils and group 2 innate lymphoid cells (ILC2). We have reported that NP contain elevated levels of B cells and antibodies, making NP an ideal system for studying B cells in the airways...
December 21, 2016: Clinical and Experimental Allergy: Journal of the British Society for Allergy and Clinical Immunology
https://www.readbyqxmd.com/read/27998928/the-cell-cycle-restricts-activation-induced-cytidine-deaminase-activity-to-early-g1
#18
Qiao Wang, Kyong-Rim Kieffer-Kwon, Thiago Y Oliveira, Christian T Mayer, Kaihui Yao, Joy Pai, Zhen Cao, Marei Dose, Rafael Casellas, Mila Jankovic, Michel C Nussenzweig, Davide F Robbiani
Activation-induced cytidine deaminase (AID) converts cytosine into uracil to initiate somatic hypermutation (SHM) and class switch recombination (CSR) of antibody genes. In addition, this enzyme produces DNA lesions at off-target sites that lead to mutations and chromosome translocations. However, AID is mostly cytoplasmic, and how and exactly when it accesses nuclear DNA remains enigmatic. Here, we show that AID is transiently in spatial contact with genomic DNA from the time the nuclear membrane breaks down in prometaphase until early G1, when it is actively exported into the cytoplasm...
January 2017: Journal of Experimental Medicine
https://www.readbyqxmd.com/read/27997339/toll-like-receptor-3-adjuvant-in-combination-with-virus-like-particles-elicit-a-humoral-response-against-hiv
#19
Ethan Poteet, Phoebe Lewis, Changyi Chen, Sam On Ho, Thai Do, SuMing Chiang, Celia Labranche, David Montefiori, Gary Fujii, Qizhi Yao
Human Immunodeficiency Virus (HIV) Virus-Like Particles (VLPs) composed of HIVIIIB Gag and HIVBaL gp120/gp41 envelope are a pseudovirion vaccine capable of presenting antigens in their native conformations. To enhance the immunogenicity of the HIV Env antigen, VLPs were coupled to VesiVax Conjugatable Adjuvant Lipid Vesicles (CALV) containing one of four toll-like-receptor (TLR) ligands, each activating a receptor with distinct cellular localization and downstream pathways. C57BL/6 mice were vaccinated by intranasal prime followed by two sub-cheek boosts and their sera immunoglobulin and neutralizing potency were measured over a duration of 3months after vaccination...
November 21, 2016: Vaccine
https://www.readbyqxmd.com/read/27974461/the-gs-protein-coupled-a2a-adenosine-receptor-controls-t-cell-help-in-the-germinal-center
#20
Robert K Abbott, Murillo Silva, Jasmine Labuda, Molly Thayer, Derek W Cain, Phaethon Philbrook, Shalini Sethumadhavan, Stephen Hatfield, Akio Ohta, Michail Sitkovsky
T follicular helper (TFH) cells have been shown to be critically required for the germinal center (GC) reaction where B cells undergo class switch recombination and clonal selection to generate high affinity neutralizing antibodies. However, detailed knowledge of the physiological cues within the GC microenvironment that regulate T cell help is limited. The cAMP-elevating, Gs protein-coupled A2a adenosine receptor (A2aR) is an evolutionarily conserved receptor that limits and redirects cellular immunity. However, the role of A2aR in humoral immunity and B cell differentiation is unknown...
January 27, 2017: Journal of Biological Chemistry
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