101
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Boehm T, Iwanami N, Hess I. Evolution of the immune system in the lower vertebrates. Annu Rev Genomics Hum Genet 2012; 13:127-49. [PMID: 22703179 DOI: 10.1146/annurev-genom-090711-163747] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The evolutionary emergence of vertebrates was accompanied by the invention of adaptive immunity. This is characterized by extraordinarily diverse repertoires of somatically assembled antigen receptors and the facility of antigen-specific memory, leading to more rapid and efficient secondary immune responses. Adaptive immunity emerged twice during early vertebrate evolution, once in the lineage leading to jawless fishes (such as lamprey and hagfish) and, independently, in the lineage leading to jawed vertebrates (comprising the overwhelming majority of extant vertebrates, from cartilaginous fishes to mammals). Recent findings on the immune systems of jawless and jawed fishes (here referred to as lower vertebrates) impact on the identification of general principles governing the structure and function of adaptive immunity and its coevolution with innate defenses. The discovery of conserved features of adaptive immunity will guide attempts to generate synthetic immunological functionalities and thus provide new avenues for intervening with faulty immune functions in humans.
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Affiliation(s)
- Thomas Boehm
- Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany.
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102
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Yabuki M, Cummings WJ, Leppard JB, Immormino RM, Wood CL, Allison DS, Gray PW, Tjoelker LW, Maizels N. Antibody discovery ex vivo accelerated by the LacO/LacI regulatory network. PLoS One 2012; 7:e36032. [PMID: 22558313 PMCID: PMC3338700 DOI: 10.1371/journal.pone.0036032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 03/27/2012] [Indexed: 11/18/2022] Open
Abstract
Monoclonal antibodies (mAbs) can be potent and highly specific therapeutics, diagnostics and research reagents. Nonetheless, mAb discovery using current in vivo or in vitro approaches can be costly and time-consuming, with no guarantee of success. We have established a platform for rapid discovery and optimization of mAbs ex vivo. This DTLacO platform derives from a chicken B cell line that has been engineered to enable rapid selection and seamless maturation of high affinity mAbs. We have validated the DTLacO platform by generation of high affinity and specific mAbs to five cell surface targets, the receptor tyrosine kinases VEGFR2 and TIE2, the glycoprotein TROP2, the small TNF receptor family member FN14, and the G protein-coupled receptor FZD10. mAb discovery is rapid and humanization is straightforward, establishing the utility of the DTLacO platform for identification of mAbs for therapeutic and other applications.
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Affiliation(s)
- Munehisa Yabuki
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
- XORI Corporation, Seattle, Washington, United States of America
| | - W. Jason Cummings
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
- XORI Corporation, Seattle, Washington, United States of America
| | - John B. Leppard
- XORI Corporation, Seattle, Washington, United States of America
| | - Robert M. Immormino
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Christi L. Wood
- XORI Corporation, Seattle, Washington, United States of America
| | | | - Patrick W. Gray
- Accelerator Corporation, Seattle, Washington, United States of America
| | | | - Nancy Maizels
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington, United States of America
- * E-mail:
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103
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Antibody repertoire development in fetal and neonatal piglets. XXIII: fetal piglets infected with a vaccine strain of PRRS Virus display the same immune dysregulation seen in isolator piglets. Vaccine 2012; 30:3646-52. [PMID: 22465749 DOI: 10.1016/j.vaccine.2012.03.038] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 02/28/2012] [Accepted: 03/16/2012] [Indexed: 01/22/2023]
Abstract
The Ig levels and antibody repertoire diversification in fetal piglets infected with an attenuated Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) were measured. Serum Ig levels were greatly elevated in PRRSV-infected fetuses; IgG was elevated >50-fold, IgM>5-15-fold and IgA>2-fold compared to control fetuses. Their IgM to IgG to IgA profile was the same as that in isolator piglets infected for the same period with wild-type PRRSV. Fetal animals showed less repertoire diversification than even isolator piglets that were maintained germfree (GF) while the repertoire diversification index (RDI) for PRRSV-infected isolator piglets was 10-fold higher and comparable to littermates infected with swine influenza (S-FLU). However, when expressed as the RDI:Ig ratio, infected fetuses appeared 10-fold less capable of repertoire diversification than uninfected littermates and GF isolator piglets. Compared to S-FLU isolator piglets that resolve the infection, the RDI:Ig of PRRSV-infected isolator piglets was 100-fold lower. Overall, infection of fetuses with an attenuated virus shows the same immune dysregulation seen postnatally in wild type infected isolator piglets, indicating that: (a) attenuation did not alter the ability of the virus to cause dysregulation and (b) the isolator infectious model reflects the fetal disease.
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104
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Abstract
Lampreys and hagfish are primitive jawless vertebrates capable of mounting specific immune responses. Lampreys possess different types of lymphocytes, akin to T and B cells of jawed vertebrates, that clonally express somatically diversified antigen receptors termed variable lymphocyte receptors (VLRs), which are composed of tandem arrays of leucine-rich repeats. The VLRs appear to be diversified by a gene conversion mechanism involving lineage-specific cytosine deaminases. VLRA is expressed on the surface of T-like lymphocytes; B-like lymphocytes express and secrete VLRB as a multivalent protein. VLRC is expressed by a distinct lymphocyte lineage. VLRA-expressing cells appear to develop in a thymus-like tissue at the tip of gill filaments, and VLRB-expressing cells develop in hematopoietic tissues. Reciprocal expression patterns of evolutionarily conserved interleukins and chemokines possibly underlie cell-cell interactions during an immune response. The discovery of VLRs in agnathans illuminates the origins of adaptive immunity in early vertebrates.
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Affiliation(s)
- Thomas Boehm
- Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany
| | - Nathanael McCurley
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Yoichi Sutoh
- Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Michael Schorpp
- Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany
| | - Masanori Kasahara
- Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Max D. Cooper
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia 30322
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105
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Sale JE. Measurement of diversification in the immunoglobulin light chain gene of DT40 cells. Methods Mol Biol 2012; 920:417-32. [PMID: 22941620 DOI: 10.1007/978-1-61779-998-3_29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The immunoglobulin loci of the genetically tractable chicken B cell line DT40 provide a unique opportunity to study the cellular response to endogenously generated DNA damage in a chromosomal context. Abasic sites generated by the concerted action of Activation-Induced Deaminase (AID) and Uracil DNA Glycosylase result in both homologous recombination-dependent gene conversion and translesion synthesis-dependent point mutations. The system has provided important insights into both the early stages of AID-dependent immunoglobulin gene diversification and into the relationship between pathways of DNA damage bypass. Here we describe the assays that can be employed to monitor the rate and pattern of immunoglobulin gene diversification at the light chain locus of DT40.
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Affiliation(s)
- Julian E Sale
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
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106
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Wu L, Oficjalska K, Lambert M, Fennell BJ, Darmanin-Sheehan A, Ní Shúilleabháin D, Autin B, Cummins E, Tchistiakova L, Bloom L, Paulsen J, Gill D, Cunningham O, Finlay WJJ. Fundamental characteristics of the immunoglobulin VH repertoire of chickens in comparison with those of humans, mice, and camelids. THE JOURNAL OF IMMUNOLOGY 2011; 188:322-33. [PMID: 22131336 DOI: 10.4049/jimmunol.1102466] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Examination of 1269 unique naive chicken V(H) sequences showed that the majority of positions in the framework (FW) regions were maintained as germline, with high mutation rates observed in the CDRs. Many FW mutations could be clearly related to the modulation of CDR structure or the V(H)-V(L) interface. CDRs 1 and 2 of the V(H) exhibited frequent mutation in solvent-exposed positions, but conservation of common structural residues also found in human CDRs at the same positions. In comparison with humans and mice, the chicken CDR3 repertoire was skewed toward longer sequences, was dominated by small amino acids (G/S/A/C/T), and had higher cysteine (chicken, 9.4%; human, 1.6%; and mouse, 0.25%) but lower tyrosine content (chicken, 9.2%; human, 16.8%; and mouse 26.4%). A strong correlation (R(2) = 0.97) was observed between increasing CDR3 length and higher cysteine content. This suggests that noncanonical disulfides are strongly favored in chickens, potentially increasing CDR stability and complexity in the topology of the combining site. The probable formation of disulfide bonds between CDR3 and CDR1, FW2, or CDR2 was also observed, as described in camelids. All features of the naive repertoire were fully replicated in the target-selected, phage-displayed repertoire. The isolation of a chicken Fab with four noncanonical cysteines in the V(H) that exhibits 64 nM (K(D)) binding affinity for its target proved these constituents to be part of the humoral response, not artifacts. This study supports the hypothesis that disulfide bond-constrained CDR3s are a structural diversification strategy in the restricted germline v-gene repertoire of chickens.
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Affiliation(s)
- Leeying Wu
- Global Biotherapeutics Technologies, Pfizer, Cambridge, MA 02140, USA
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107
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Duong BH, Ota T, Aoki-Ota M, Cooper AB, Ait-Azzouzene D, Vela JL, Gavin AL, Nemazee D. Negative selection by IgM superantigen defines a B cell central tolerance compartment and reveals mutations allowing escape. THE JOURNAL OF IMMUNOLOGY 2011; 187:5596-605. [PMID: 22043016 DOI: 10.4049/jimmunol.1102479] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To analyze B lymphocyte central tolerance in a polyclonal immune system, mice were engineered to express a superantigen reactive to IgM of allotype b (IgM(b)). IgM(b/b) mice carrying superantigen were severely B cell lymphopenic, but small numbers of B cells matured. Their sera contained low levels of IgG and occasionally high levels of IgA. In bone marrow, immature B cells were normal in number, but internalized IgM and had a unique gene expression profile, compared with those expressing high levels of surface IgM, including elevated recombinase activator gene expression. A comparable B cell population was defined in wild-type bone marrows, with an abundance suggesting that at steady state ∼20% of normal developing B cells are constantly encountering autoantigens in situ. In superantigen-expressing mice, as well as in mice carrying the 3H9 anti-DNA IgH transgene, or 3H9 H along with mutation in the murine κ-deleting element RS, IgM internalization was correlated with CD19 downmodulation. CD19(low) bone marrow cells from 3H9;RS(-/-) mice were enriched in L chains that promote DNA binding. Our results suggest that central tolerance and attendant L chain receptor editing affect a large fraction of normal developing B cells. IgH(a/b) mice carrying the superantigen had a ∼50% loss in follicular B cell numbers, suggesting that escape from central tolerance by receptor editing from one IgH allele to another was not a major mechanism. IgM(b) superantigen hosts reconstituted with experimental bone marrow were demonstrated to be useful in revealing pathways involved in central tolerance.
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Affiliation(s)
- Bao Hoa Duong
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
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108
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Butler JE, Santiago-Mateo K, Sun XZ, Wertz N, Sinkora M, Francis DH. Antibody Repertoire Development in Fetal and Neonatal Piglets. XX. B Cell Lymphogenesis Is Absent in the Ileal Peyer’s Patches, Their Repertoire Development Is Antigen Dependent, and They Are Not Required for B Cell Maintenance. THE JOURNAL OF IMMUNOLOGY 2011; 187:5141-9. [DOI: 10.4049/jimmunol.1101871] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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109
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Kuraoka M, McWilliams L, Kelsoe G. AID expression during B-cell development: searching for answers. Immunol Res 2011; 49:3-13. [PMID: 21136202 DOI: 10.1007/s12026-010-8185-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Expression of activation-induced cytidine deaminase (AID) by germinal center (GC) B cells drives the processes of immunoglobulin (Ig) somatic hypermutation (SHM) and class switch recombination (CSR) necessary for the generation of high affinity IgG serum antibody and the memory B-cell compartment. Increasing evidence indicates that AID is also expressed at low levels in developing B cells but to date, this early, developmentally regulated AID expression has no known function. Does the timing and extent of AID expression in developmentally immature, non-GC B cells provide clues to reveal its physiologic role?
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Affiliation(s)
- Masayuki Kuraoka
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
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110
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Magor KE. Immunoglobulin genetics and antibody responses to influenza in ducks. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2011; 35:1008-16. [PMID: 21377488 DOI: 10.1016/j.dci.2011.02.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 02/23/2011] [Accepted: 02/25/2011] [Indexed: 05/24/2023]
Abstract
The role of the duck as the natural host and reservoir of influenza and efforts to vaccinate ducks during recent outbreaks of avian influenza has renewed interest in the duck antibody response. Ducks have unique antibody structures and expression, with consequences for their function. Aspects of immunoglobulin genetics, gene expression, and antibody function will be reviewed in the context of the duck immune response to influenza. Ducks have three immunoglobulin isotypes, IgM, IgA and IgY in translocon arrangement. The order of heavy chain genes in the locus is unusual, IGHM, IGHA and IGHY, with IGHA in inverse transcriptional orientation. IgH and IgL gene rearrangement in ducks involves limited V, (D) and J element recombination and diversity is generated by gene conversion from pseudogenes. IgY, the functional equivalent of IgG, is produced in two secreted forms, a full-length form and one lacking the third and fourth C region domains, which predominates later in the immune response and lacks the biological effector functions of IgG. The unusual features of duck antibodies may contribute to weak antibody responses and the perpetuation of the virus in this animal reservoir.
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Affiliation(s)
- Katharine E Magor
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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111
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Nakamura N, Aoki Y, Horiuchi H, Furusawa S, Yamanaka HI, Kitamoto T, Matsuda H. Construction of recombinant monoclonal antibodies from a chicken hybridoma line secreting specific antibody. Cytotechnology 2011; 32:191-8. [PMID: 19002980 DOI: 10.1023/a:1008149815908] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The chicken is a useful animal for the development of the specificantibodies against the mammalian conserved proteins. We generated twotypes of recombinant chicken monoclonal antibodies (mAbs), using a phagedisplay technique from a chicken hybridoma HUC2-13 which secreted themAb to the N-terminal of the mammalian prion protein (PrP). Althoughthe mAb HUC2-13 is a useful antibody for the prion research, thehybridoma produces a low level of antibody production. In order to producea large amount of the mAb, we have constructed a single chain fragmentvariable region (scF(V)) mAb by using the variable heavy(V(H)) and light (V(L))genes which were amplified by using the two primer pairs and theflexible linker. The two phage display mAbs (HUC2p3 and HUC2p5)expressed on a M13 filamentous phage and their soluble type mAbs(HUC2s3 and HUC2s5) were reacted with the PrP peptide antigen in theELISA. In the Western blot analysis, the mAbs HUC2p3 and HUC2s3 wereas reactive to PrP(c) from mouse brains as the mAb HUC2-13 was. The nucleotide sequences of V(H) and V(L) genes from HUC2-13 and the two cloneswere identical except for only one residue. These results indicate that themethods presented here provide an effective tool for the improvement ofthe low levels of antibody production in the chicken hybridoma system.
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Affiliation(s)
- N Nakamura
- Department of Immunobiology, Faculty of Applied Biological Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528, Japan
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112
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Fawcett JA, Innan H. Neutral and non-neutral evolution of duplicated genes with gene conversion. Genes (Basel) 2011; 2:191-209. [PMID: 24710144 PMCID: PMC3924837 DOI: 10.3390/genes2010191] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 01/20/2011] [Accepted: 02/12/2011] [Indexed: 01/11/2023] Open
Abstract
Gene conversion is one of the major mutational mechanisms involved in the DNA sequence evolution of duplicated genes. It contributes to create unique patters of DNA polymorphism within species and divergence between species. A typical pattern is so-called concerted evolution, in which the divergence between duplicates is maintained low for a long time because of frequent exchanges of DNA fragments. In addition, gene conversion affects the DNA evolution of duplicates in various ways especially when selection operates. Here, we review theoretical models to understand the evolution of duplicates in both neutral and non-neutral cases. We also explain how these theories contribute to interpreting real polymorphism and divergence data by using some intriguing examples.
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Affiliation(s)
- Jeffrey A Fawcett
- Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan.
| | - Hideki Innan
- Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan.
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113
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Ling F, Mikawa T, Shibata T. Enlightenment of yeast mitochondrial homoplasmy: diversified roles of gene conversion. Genes (Basel) 2011; 2:169-90. [PMID: 24710143 PMCID: PMC3924846 DOI: 10.3390/genes2010169] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 01/18/2011] [Accepted: 01/25/2011] [Indexed: 11/29/2022] Open
Abstract
Mitochondria have their own genomic DNA. Unlike the nuclear genome, each cell contains hundreds to thousands of copies of mitochondrial DNA (mtDNA). The copies of mtDNA tend to have heterogeneous sequences, due to the high frequency of mutagenesis, but are quickly homogenized within a cell ("homoplasmy") during vegetative cell growth or through a few sexual generations. Heteroplasmy is strongly associated with mitochondrial diseases, diabetes and aging. Recent studies revealed that the yeast cell has the machinery to homogenize mtDNA, using a common DNA processing pathway with gene conversion; i.e., both genetic events are initiated by a double-stranded break, which is processed into 3' single-stranded tails. One of the tails is base-paired with the complementary sequence of the recipient double-stranded DNA to form a D-loop (homologous pairing), in which repair DNA synthesis is initiated to restore the sequence lost by the breakage. Gene conversion generates sequence diversity, depending on the divergence between the donor and recipient sequences, especially when it occurs among a number of copies of a DNA sequence family with some sequence variations, such as in immunoglobulin diversification in chicken. MtDNA can be regarded as a sequence family, in which the members tend to be diversified by a high frequency of spontaneous mutagenesis. Thus, it would be interesting to determine why and how double-stranded breakage and D-loop formation induce sequence homogenization in mitochondria and sequence diversification in nuclear DNA. We will review the mechanisms and roles of mtDNA homoplasmy, in contrast to nuclear gene conversion, which diversifies gene and genome sequences, to provide clues toward understanding how the common DNA processing pathway results in such divergent outcomes.
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Affiliation(s)
- Feng Ling
- Chemical Genetics Laboratory, RIKEN Advanced Science Institute/2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
| | - Tsutomu Mikawa
- Biometal Science Laboratory, RIKEN SPring-8 Center/Mikazuki cho, Hyogo 679-5148 Japan.
| | - Takehiko Shibata
- Division of Molecular and Cellular Physiology, Department of Supramolecular Biology, Graduate School of Nanobiosciences, Yokohama City University/1-7-29 Suehiro cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
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114
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Qin T, Ren LM, Meng QY. Junctional Diversity in <I>Xenopus tropicalis</I> Immunoglobulin Light Chains. PROG BIOCHEM BIOPHYS 2011. [DOI: 10.3724/sp.j.1206.2010.00232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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115
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Abstract
Approximately 500 million years ago, two types of recombinatorial adaptive immune systems (AISs) arose in vertebrates. The jawed vertebrates diversify their repertoire of immunoglobulin domain-based T and B cell antigen receptors mainly through the rearrangement of V(D)J gene segments and somatic hypermutation, but none of the fundamental AIS recognition elements in jawed vertebrates have been found in jawless vertebrates. Instead, the AIS of jawless vertebrates is based on variable lymphocyte receptors (VLRs) that are generated through recombinatorial usage of a large panel of highly diverse leucine-rich-repeat (LRR) sequences. Whereas the appearance of transposon-like, recombination-activating genes contributed uniquely to the origin of the AIS in jawed vertebrates, the use of activation-induced cytidine deaminase for receptor diversification is common to both the jawed and jawless vertebrates. Despite these differences in anticipatory receptor construction, the basic AIS design featuring two interactive T and B lymphocyte arms apparently evolved in an ancestor of jawed and jawless vertebrates within the context of preexisting innate immunity and has been maintained since as a consequence of powerful and enduring selection, most probably for pathogen defense purposes.
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Affiliation(s)
- Masayuki Hirano
- Emory Vaccine Center, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA
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116
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Marianes AE, Zimmerman AM. Targets of somatic hypermutation within immunoglobulin light chain genes in zebrafish. Immunology 2010; 132:240-55. [PMID: 21070232 DOI: 10.1111/j.1365-2567.2010.03358.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In mammals, somatic hypermutation (SHM) of immunoglobulin (Ig) genes is critical for the generation of high-affinity antibodies and effective immune responses. Knowledge of sequence-specific biases in the targeting of somatic mutations can be useful for studies aimed at understanding antibody repertoires produced in response to infections, B-cell neoplasms, or autoimmune disease. To evaluate potential nucleotide targets of somatic mutation in zebrafish (Danio rerio), an enriched IgL cDNA library was constructed and > 250 randomly selected clones were sequenced and analysed. In total, 55 unique VJ-C sequences were identified encoding a total of 125 mutations. Mutations were most prevalent in V(L) with a bias towards single base transitions and increased mutation in the complementarity-determining regions (CDRs). Overall, mutations were overrepresented at WRCH/DGYW motifs suggestive of activation-induced cytidine deaminase (AID) targeting which is common in mice and humans. In contrast to mammalian models, N and P addition was not observed and mutations at AID hotspots were largely restricted to palindromic WRCH/DGYW motifs. Mutability indexes for di- and trinucleotide combinations confirmed C/G targets within WRCH/DGYW motifs to be statistically significant mutational hotspots and showed trinucleotides ATC and ATG to be mutation coldspots. Additive mutations in VJ-C sequences revealed patterns of clonal expansion consistent with affinity maturation responses seen in higher vertebrates. Taken together, the data reveal specific nucleotide targets of SHM in zebrafish and suggest that AID and affinity maturation contribute to antibody diversification in this emerging immunological model.
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Affiliation(s)
- Alexis E Marianes
- Department of Biology, College of Charleston, Charleston, SC 29424, USA
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117
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Lin W, Kurosawa K, Murayama A, Kagaya E, Ohta K. B-cell display-based one-step method to generate chimeric human IgG monoclonal antibodies. Nucleic Acids Res 2010; 39:e14. [PMID: 21062829 PMCID: PMC3035438 DOI: 10.1093/nar/gkq1122] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The recent development of screening strategies based on the generation and display of large libraries of antibody fragments has allowed considerable advances for the in vitro isolation of monoclonal antibodies (mAbs). We previously developed a technology referred to as the ‘ADLib (Autonomously Diversifying Library) system’, which allows the rapid screening and isolation in vitro of antigen-specific monoclonal antibodies (mAbs) from libraries of immunoglobulin M (IgM) displayed by the chicken B-cell line DT40. Here, we report a novel application of the ADLib system to the production of chimeric human mAbs. We have designed gene knock-in constructs to generate DT40 strains that coexpress chimeric human IgG and chicken IgM via B-cell-specific RNA alternative splicing. We demonstrate that the application of the ADLib system to these strains allows the one-step selection of antigen-specific human chimeric IgG. In addition, the production of chimeric IgG can be selectively increased when we modulate RNA processing by overexpressing the polyadenylation factor CstF-64. This method provides a new way to efficiently design mAbs suitable for a wide range of purposes including antibody therapy.
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Affiliation(s)
- Waka Lin
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
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118
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Kajita M, Okazawa T, Ikeda M, Todo K, Magari M, Kanayama N, Ohmori H. Efficient affinity maturation of antibodies in an engineered chicken B cell line DT40-SW by increasing point mutation. J Biosci Bioeng 2010; 110:351-8. [DOI: 10.1016/j.jbiosc.2010.03.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 03/02/2010] [Accepted: 03/11/2010] [Indexed: 10/19/2022]
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119
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Koti M, Kataeva G, Kaushik AK. Novel atypical nucleotide insertions specifically at VH-DH junction generate exceptionally long CDR3H in cattle antibodies. Mol Immunol 2010; 47:2119-28. [PMID: 20435350 DOI: 10.1016/j.molimm.2010.02.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 02/21/2010] [Indexed: 11/25/2022]
Abstract
Some IgM cattle antibodies are amongst the largest known to exist in jawed vertebrates where CDR3H size may extend up to 61 amino acids. To understand the origin of such an exceptionally long CDR3H, bovine D(H) gene locus was completely characterized from Holstein cattle that revealed the presence of a total of eight D(H) genes, including D(H)Q52, with a distinct organization in sub-clusters. However, a total of 10 D(H) genes are identified at the polymorphic D-gene locus in cattle that are classified into four families, designated as BovD(H)A, BovD(H)B, BovD(H)C and BovD(H)D. In fetal B-cells, VDJ recombinations encoding long CDR3H (>50 codons) are directly encoded by the single germline V(H) gl.110.20, the longest D(H)2 and the J(H)1 genes, apart from few N- and P-nucleotide additions at the junctions. Further, non J-proximal D(H)7 gene is preferentially expressed in fetal B cells. The adult VDJ recombinations, however, are distinctly remarkable for 'conserved short nucleotide sequence' ('CSNS'; 13-18 nucleotides), of non-V(H) or D(H) gene origin, inserted specifically at V(H)-D(H) junctions resulting in extension of CDR3H size up to 61 codons. Together with P-nucleotides, N-additions (1-9 nucleotides) are noted at both the V(H)-D(H) and D(H)-J(H) junctions. Such 'CSNS' insertions at V(H)-D(H) junction of adult VDJ recombinations encoding exceptionally long CDR3H provide novel mechanism of antibody diversification in cattle, not yet observed in other species. Further, analysis of V(H)-D(H)-J(H) recombinations originating from fetal B-cells reveals the presence of substitution, deletion or addition mutations without prior exposure to external antigen. Thus, somatic hypermutations may contribute towards diversification of the developing nascent antibody repertoire in cattle. In conclusion, the outlined experiments provide novel antibody diversification mechanism via 'CSNS' insertions, specifically at the V(H)-D(H) junction, in generating exceptionally long CDR3H extending up to 61 codons in cattle antibodies.
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Affiliation(s)
- Madhuri Koti
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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120
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Kohzaki M, Nishihara K, Hirota K, Sonoda E, Yoshimura M, Ekino S, Butler JE, Watanabe M, Halazonetis TD, Takeda S. DNA polymerases nu and theta are required for efficient immunoglobulin V gene diversification in chicken. J Cell Biol 2010; 189:1117-27. [PMID: 20584917 PMCID: PMC2894443 DOI: 10.1083/jcb.200912012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Accepted: 05/26/2010] [Indexed: 01/10/2023] Open
Abstract
The chicken DT40 B lymphocyte line diversifies its immunoglobulin (Ig) V genes through translesion DNA synthesis-dependent point mutations (Ig hypermutation) and homologous recombination (HR)-dependent Ig gene conversion. The error-prone biochemical characteristic of the A family DNA polymerases Polnu and Pol led us to explore the role of these polymerases in Ig gene diversification in DT40 cells. Disruption of both polymerases causes a significant decrease in Ig gene conversion events, although POLN(-/-)/POLQ(-/-) cells exhibit no prominent defect in HR-mediated DNA repair, as indicated by no increase in sensitivity to camptothecin. Poleta has also been previously implicated in Ig gene conversion. We show that a POLH(-/-)/POLN(-/-)/POLQ(-/-) triple mutant displays no Ig gene conversion and reduced Ig hypermutation. Together, these data define a role for Polnu and Pol in recombination and suggest that the DNA synthesis associated with Ig gene conversion is accounted for by three specialized DNA polymerases.
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Affiliation(s)
- Masaoki Kohzaki
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
- Research Reactor Institute, Kyoto University, Sennan-gun, Osaka 590-0494, Japan
- Department of Molecular Biology, University of Geneva, Geneva 4 CH-1211, Switzerland
| | - Kana Nishihara
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
- Department of Food and Nutrition, Kyoto Women’s University, Higashiyama-ku, Kyoto 606-8501, Japan
| | - Kouji Hirota
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Eiichiro Sonoda
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Michio Yoshimura
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shigeo Ekino
- Department of Histology, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto 860-8556, Japan
| | - John E. Butler
- Department of Microbiology, University of Iowa Medical School, Iowa City, IA 52242
| | - Masami Watanabe
- Research Reactor Institute, Kyoto University, Sennan-gun, Osaka 590-0494, Japan
| | - Thanos D. Halazonetis
- Department of Molecular Biology, University of Geneva, Geneva 4 CH-1211, Switzerland
| | - Shunichi Takeda
- Department of Radiation Genetics and Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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121
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A. Higgins D, Ko OKH, Chan SWS. Duck antibody responses to keyhole limpet haemocyanin, human immunoglobulin G and the trinitrophenyl hapten. Evidence of affinity maturation. Avian Pathol 2010; 30:381-90. [DOI: 10.1080/03079450120066386] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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122
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Kurosawa K, Lin W, Ohta K. Distinct roles of HDAC1 and HDAC2 in transcription and recombination at the immunoglobulin loci in the chicken B cell line DT40. ACTA ACUST UNITED AC 2010; 148:201-7. [DOI: 10.1093/jb/mvq054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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123
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Wu Q, Wei Z, Yang Z, Wang T, Ren L, Hu X, Meng Q, Guo Y, Zhu Q, Robert J, Hammarström L, Li N, Zhao Y. Phylogeny, genomic organization and expression of lambda and kappa immunoglobulin light chain genes in a reptile, Anolis carolinensis. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2010; 34:579-589. [PMID: 20056120 DOI: 10.1016/j.dci.2009.12.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 12/23/2009] [Accepted: 12/30/2009] [Indexed: 05/28/2023]
Abstract
The reptiles are the last major taxon of jawed vertebrates in which immunoglobulin light chain isotypes have not been well characterized. Using the recently released genome sequencing data, we show in this study that the reptile Anolis carolinensis expresses both lambda and kappa light chain genes. The genomic organization of both gene loci is structurally similar to their respective counterparts in mammals. The identified lambda locus contains three constant region genes each preceded by a joining gene segment, and a total of 37 variable gene segments. In contrast, the kappa locus contains only a single constant region gene, and two joining gene segments with a single family of 14 variable gene segments located upstream. Analysis of junctions of the recombined VJ transcripts reveals a paucity of N and P nucleotides in both expressed lambda and kappa sequences. These results help us to understand the generation of the immunoglobulin repertoire in reptiles and immunoglobulin evolution in vertebrates.
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Affiliation(s)
- Qian Wu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, PR China
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124
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Das S, Mohamedy U, Hirano M, Nei M, Nikolaidis N. Analysis of the immunoglobulin light chain genes in zebra finch: evolutionary implications. Mol Biol Evol 2010; 27:113-20. [PMID: 19744999 DOI: 10.1093/molbev/msp212] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
All jawed vertebrates produce immunoglobulins (IGs) as a defense mechanism against pathogens. Typically, IGs are composed of two identical heavy chains (IGH) and two identical light chains (IGL). Most tetrapod species encode more than one isotype of light chains. Chicken is the only representative of birds for which genomic information is currently available and is an exception to the above rule because it encodes only a single IGL isotype (i.e., lambda). Here, we show that the genome of zebra finch, another bird species, encodes a single IGL isotype, that is, lambda, like the chicken. These results strongly suggest that the second isotype (i.e., kappa) present in both reptiles and mammals was lost in a very early stage of bird evolution. Furthermore, we show that both chicken and zebra finch contain a single set of functional variable, joining, and constant region genes and multiple variable region pseudogenes. The latter finding suggests that this type of genomic organization was already present in the common ancestor of these bird species and remained unchanged over a long evolutionary time. This conservation is in contrast with the high levels of variation observed in the mammalian IGL loci. The presence of a single functional variable region gene followed by multiple variable pseudogenes in zebra finch suggest that this species may be generating antibody diversity by a gene conversion-like mechanism like the chicken.
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Affiliation(s)
- Sabyasachi Das
- Department of Pathology and Laboratory Medicine, Emory Vaccine Center, School of Medicine, Emory University, USA.
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125
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Alitheen NB, McClure S, McCullagh P. B-cell development: one problem, multiple solutions. Immunol Cell Biol 2010; 88:445-50. [PMID: 20084079 DOI: 10.1038/icb.2009.119] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Interspecies variations in the processes of B-cell development and repertoire generation contrast with the greater consistency of T-cell development. B-cell development in mice and humans, with postnatal B-cell generation of new repertoire in the bone marrow throughout life, is regarded as the 'standard' pattern. In contrast, accounts of B cells in birds, sheep, cattle, rabbits and pigs (the 'other' species) describe cessation of gene diversification in the perinatal period, with the gut-associated lymphoid tissue (GALT) functioning as the primary lymphoid organ thereafter. It has become customary to regard the developmental pathways of T and B cells within any individual species as being as dissimilar as the functions of the two mature cell types. Reinterpretation of B-cell development patterns in different species is overdue in response to two types of reports. The first of these describe T-B 'crossover', specifically the intrathymic production of B cells and the extrathymic production of T cells. The second attests to the extent of sharing of B-cell developmental features across the two groups of species. We propose that, as is a feature of other haematopoietic cells, a menu of alternative B- and T-cell pathways has been retained and shared across species. A single pathway usually predominates in any species, masking alternatives. The observed predominance of any pathway is determined by factors such as placental permeability, extent of maturation of the immune system by birth and the feasibility of direct experimental intervention in development.
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Affiliation(s)
- Noorjahan Banu Alitheen
- Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Selangor, Malaysia
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126
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Dias da Silva W, Tambourgi DV. IgY: a promising antibody for use in immunodiagnostic and in immunotherapy. Vet Immunol Immunopathol 2010; 135:173-80. [PMID: 20083313 PMCID: PMC7126787 DOI: 10.1016/j.vetimm.2009.12.011] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 12/16/2009] [Accepted: 12/30/2009] [Indexed: 11/26/2022]
Abstract
Immunoglobulin IgY is the major antibody produced by chickens (Gallus domesticus). After their V-C gene is rearranged in B cells, IgY is continually synthesized, excreted into the blood and transferred to the egg yolk, where it is accumulated. IgY is produced by hens to provide their offspring with an effective humoral immunity against the commonest avian pathogens until full maturation of their own immune system. In this review we aim to give an overview about the generation, structure, properties of IgY, as well as the advantages of chicken antibodies use over mammalian antibodies in immunodiagnostics and immunotherapy.
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Affiliation(s)
- Wilmar Dias da Silva
- Immunochemistry Laboratory, Butantan Institute, Av. Vital Brazil 1500, 05503-900 São Paulo, Brazil.
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127
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Flajnik MF, Kasahara M. Origin and evolution of the adaptive immune system: genetic events and selective pressures. Nat Rev Genet 2009; 11:47-59. [PMID: 19997068 DOI: 10.1038/nrg2703] [Citation(s) in RCA: 566] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The adaptive immune system (AIS) in mammals, which is centred on lymphocytes bearing antigen receptors that are generated by somatic recombination, arose approximately 500 million years ago in jawed fish. This intricate defence system consists of many molecules, mechanisms and tissues that are not present in jawless vertebrates. Two macroevolutionary events are believed to have contributed to the genesis of the AIS: the emergence of the recombination-activating gene (RAG) transposon, and two rounds of whole-genome duplication. It has recently been discovered that a non-RAG-based AIS with similarities to the jawed vertebrate AIS - including two lymphoid cell lineages - arose in jawless fish by convergent evolution. We offer insights into the latest advances in this field and speculate on the selective pressures that led to the emergence and maintenance of the AIS.
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Affiliation(s)
- Martin F Flajnik
- Department of Microbiology and Immunology, University of Maryland at Baltimore, Baltimore, Maryland 21201, USA.
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128
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NARABARA K, ABE A, HANIEH H, KONDO Y. B cell differentiation in the bursa of Fabricius and spleen of embryos and chicks immediately after hatching. Anim Sci J 2009; 80:669-77. [DOI: 10.1111/j.1740-0929.2009.00679.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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129
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Ordinario EC, Yabuki M, Handa P, Cummings WJ, Maizels N. RAD51 paralogs promote homology-directed repair at diversifying immunoglobulin V regions. BMC Mol Biol 2009; 10:98. [PMID: 19863810 PMCID: PMC2774322 DOI: 10.1186/1471-2199-10-98] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 10/28/2009] [Indexed: 01/08/2023] Open
Abstract
Background Gene conversion depends upon the same factors that carry out more general process of homologous recombination, including homologous gene targeting and recombinational repair. Among these are the RAD51 paralogs, conserved factors related to the key recombination factor, RAD51. In chicken and other fowl, gene conversion (templated mutation) diversifies immunoglobulin variable region sequences. This allows gene conversion and recombinational repair to be studied using the chicken DT40 B cell line, which carries out constitutive gene conversion and provides a robust and physiological model for homology-directed repair in vertebrate cells. Results We show that DT40 contains constitutive nuclear foci of the repair factors RAD51D and XRCC2, consistent with activated homologous recombination. Single-cell imaging of a DT40 derivative in which the rearranged and diversifying immunoglobulin λR light chain gene is tagged with polymerized lactose operator, DT40 PolyLacO-λR, showed that RAD51D and XRCC2 localize to the diversifying λR gene. Colocalizations correlate both functionally and physically with active immunoglobulin gene conversion. Ectopic expression of either RAD51D or XRCC2 accelerated the clonal rate of gene conversion, and conversion tracts were significantly longer in RAD51D than XRCC2 transfectants. Conclusion These results demonstrate direct functions of RAD51D and XRCC2 in immunoglobulin gene conversion, and also suggest that modulation of levels of repair factors may be a useful strategy to promote gene correction in other cell types.
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Affiliation(s)
- Ellen C Ordinario
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195-7650, USA.
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130
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Ordinario EC, Yabuki M, Larson RP, Maizels N. Temporal regulation of Ig gene diversification revealed by single-cell imaging. THE JOURNAL OF IMMUNOLOGY 2009; 183:4545-53. [PMID: 19748985 DOI: 10.4049/jimmunol.0900673] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Rearranged Ig V regions undergo activation-induced cytidine deaminase (AID)-initiated diversification in sequence to produce either nontemplated or templated mutations, in the related pathways of somatic hypermutation and gene conversion. In chicken DT40 B cells, gene conversion normally predominates, producing mutations templated by adjacent pseudo-V regions, but impairment of gene conversion switches mutagenesis to a nontemplated pathway. We recently showed that the activator, E2A, functions in cis to promote diversification, and that G(1) phase of cell cycle is the critical window for E2A action. By single-cell imaging of stable AID-yellow fluorescent protein transfectants, we now demonstrate that AID-yellow fluorescent protein can stably localize to the nucleus in G(1) phase, but undergoes ubiquitin-dependent proteolysis later in cell cycle. By imaging of DT40 polymerized lactose operator-lambda(R) cells, in which polymerized lactose operator tags the rearranged lambda(R) gene, we show that both the repair polymerase Poleta and the multifunctional factor MRE11/RAD50/NBS1 localize to lambda(R), and that lambda(R)/Poleta colocalizations occur predominately in G(1) phase, when they reflect repair of AID-initiated damage. We find no evidence of induction of gamma-H2AX, the phosphorylated variant histone that is a marker of double-strand breaks, and Ig gene conversion may therefore proceed by a pathway involving templated repair at DNA nicks rather than double-strand breaks. These results lead to a model in which Ig gene conversion initiates and is completed or nearly completed in G(1) phase. AID deaminates ssDNA, and restriction of mutagenesis to G(1) phase would contribute to protecting the genome from off-target attack by AID when DNA replication occurs in S phase.
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Affiliation(s)
- Ellen C Ordinario
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA
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131
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Tallmadge RL, McLaughlin K, Secor E, Ruano D, Matychak MB, Flaminio MJBF. Expression of essential B cell genes and immunoglobulin isotypes suggests active development and gene recombination during equine gestation. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2009; 33:1027-1038. [PMID: 19442687 DOI: 10.1016/j.dci.2009.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Revised: 04/30/2009] [Accepted: 05/03/2009] [Indexed: 05/27/2023]
Abstract
Many features of the equine immune system develop during fetal life, yet the naïve or immature immune state of the neonate renders the foal uniquely susceptible to particular pathogens. RT-PCR and immunohistochemical experiments investigated the progressive expression of developmental B cell markers and immunoglobulins in lymphoid tissues from equine fetus, pre-suckle neonate, foal, and adult horses. Serum IgM, IgG isotype, and IgA concentrations were also quantified in pre-suckle foals and adult horses. The expression of essential B cell genes suggests active development and gene recombination during equine gestation, including immunoglobulin isotype switching. The corresponding production of IgM and IgG proteins is detectable in a limited scale at birth. Although the equine neonate humoral response seems competent, B cell activation factors derived from antigen presenting cells and T cells may control critical developmental regulation and immunoglobulin production during the initial months of life.
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Affiliation(s)
- Rebecca L Tallmadge
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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132
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Kim Y, Tian M. NF-kappaB family of transcription factor facilitates gene conversion in chicken B cells. Mol Immunol 2009; 46:3283-91. [PMID: 19699530 DOI: 10.1016/j.molimm.2009.07.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Accepted: 07/26/2009] [Indexed: 12/21/2022]
Abstract
Activation-induced cytidine deaminase (AID) is critical for immunoglobulin (Ig) diversification in B cells. The majority of evidence supports the model that AID modifies Ig genes at the DNA level by deaminating cytosines into uracils. The mutagenic activity is largely restricted to Ig genes to avoid genomic damage in general, but the underlying mechanism is not understood. We addressed this question in chicken B cell line DT40. We characterized a regulatory region within the Iglambda locus. This regulatory region is important for AID-mediated gene conversion at the Iglambda locus, and is capable of targeting AID activity to ectopic loci. This regulatory region contains binding sites for transcription factors NF-kappaB, Mef2 and octamer binding proteins. Mutation of these binding sites or ablation of NF-kappaB family member, p50 or c-Rel, impairs the AID targeting function of this regulatory region. These results suggest that NF-kappaB family of transcription factors contribute to AID-mediated gene conversion.
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Affiliation(s)
- Yonghwan Kim
- Section of Molecular Genetics and Microbiology, University of Texas at Austin, 1 University Station, Austin, TX 78712, USA
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133
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Comparative studies on the secondary lymphoid tissue areas in the chicken bursa of Fabricius and calf ileal Peyer's patch. Vet Immunol Immunopathol 2009; 133:190-7. [PMID: 19735947 DOI: 10.1016/j.vetimm.2009.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 07/25/2009] [Accepted: 08/03/2009] [Indexed: 11/22/2022]
Abstract
The chicken bursa of Fabricius and calf ileal Peyer's patch are thought to be the primary lymphoid organs of B cell development. In the bursa, the existence of secondary lymphoid tissue, called the diffusely infiltrated area, has been recognized. Recently, we have found the presence of a region of secondary lymphoid tissue in the ileal Peyer's patch at the period of the most rapid growth of this organ. In this study, we compared the development of these secondary lymphoid tissue regions in the bursa and ileal Peyer's patch histologically. Before hatching, lymphatic follicle formation occurred in the bursa, but not in the diffusely infiltrated area, where only a small number of lymphoid cells were found. However, during fetal calf development, lymphatic follicle formation occurred not only in the primary lymphoid organ but also in the secondary lymphoid tissue regions. Therefore, the prenatal development of the secondary lymphoid tissue regions of the bursa and ileal Peyer's patch were distinct. After hatching, formation of the germinal center, which contained many CD4+ cells, was observed in the diffusely infiltrated area of the bursa. After birth, many CD4+ cells and IgG mRNA expression were observed in the lymphatic follicle of the secondary lymphoid tissue regions in the ileal Peyer's patch, but rarely in the ileal Peyer's patch lymphatic follicles. The change of character of these secondary lymphoid tissue regions at the postnatal stage might be dependent on external antigens.
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134
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Kuraoka M, Liao D, Yang K, Allgood SD, Levesque MC, Kelsoe G, Ueda Y. Activation-induced cytidine deaminase expression and activity in the absence of germinal centers: insights into hyper-IgM syndrome. THE JOURNAL OF IMMUNOLOGY 2009; 183:3237-48. [PMID: 19667096 DOI: 10.4049/jimmunol.0901548] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Somatic hypermutation normally occurs as a consequence of the expression of activation-induced cytidine deaminase (AID) by Ag-activated, mature B cells during T cell-dependent germinal center responses. Nonetheless, despite their inability to express CD154 and initiate GC responses, patients with type 1 hyper-IgM syndrome (HIGM1) support populations of IgM(+)IgD(+)CD27(+) B cells that express mutated Ig genes. The origin of these mutated B cells is unknown; the IgM(+)IgD(+)CD27(+) cells do not express AID and appear to acquire mutations independent of stringent selection by Ag. Here, we demonstrate that immature/transitional 1 B cells from the bone marrow of CD154-deficient mice express AID and acquire Ig mutations that lack the hallmarks of antigenic selection via BCR signaling. Comparable levels of AID expression was found in developmentally immature B cells recovered from murine fetal liver and from human immature/transitional 1 B cells recovered from umbilical cord blood. AID expression in human fetal liver was also robust, approaching that of human tonsil tissue and the human germinal center B cell line, Ramos. These observations led us to conclude that AID expression in developing human B cells is the origin of the mutated IgM(+)IgD(+)CD27(+) B cells present in HIGM1 patients, and we propose that both mice and humans share a latent, AID-dependent pathway for the preimmune diversification of B lymphocytes that is more prominent in chicken, sheep, and rabbits.
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Affiliation(s)
- Masayuki Kuraoka
- Department of Immunology, Duke University, Durham, NC 27710, USA
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135
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136
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Identification of Igσ and Igλ in channel catfish, Ictalurus punctatus, and Igλ in Atlantic cod, Gadus morhua. Immunogenetics 2009; 61:353-70. [DOI: 10.1007/s00251-009-0365-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Accepted: 03/02/2009] [Indexed: 10/21/2022]
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137
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Arakawa H, Buerstedde JM. Activation-induced cytidine deaminase-mediated hypermutation in the DT40 cell line. Philos Trans R Soc Lond B Biol Sci 2009; 364:639-44. [PMID: 19008193 DOI: 10.1098/rstb.2008.0202] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Depending on the species and the developmental stage of B cells, activation-induced cytidine deaminase (AID) triggers immunoglobulin (Ig) gene diversification by gene conversion, hypermutation or switch recombination. The bursal B cell line DT40 usually diversifies its rearranged Ig light chain (IgL) gene by gene conversion, but disruption of the RAD51 gene paralogues or deletion of the psiV conversion donors induces hypermutation. Although not all aspects of somatic hypermutation can be studied in DT40, the compact size of the chicken IgL locus and the ability to modify the genome by targeted integration are powerful experimental advantages. We review here how the studies in DT40 contributed to understanding how AID initiates Ig gene diversification and how AID-induced uracils are subsequently processed by uracil DNA glycosylase, proliferating cell nuclear antigens and error-prone polymerases. We also discuss the on-going research on the Ig locus specificity of hypermutation and the possibility of using hypermutation for the artificial evolution of proteins and regulatory sequences in DT40.
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Affiliation(s)
- Hiroshi Arakawa
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute for Molecular Radiobiology, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany
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138
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Chiliza TE, Van Wyngaardt W, Du Plessis DH. Single-Chain Antibody Fragments from a Display Library Derived from Chickens Immunized with a Mixture of Parasite and Viral Antigens. Hybridoma (Larchmt) 2008; 27:413-21. [DOI: 10.1089/hyb.2008.0051] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Thamsanqa E. Chiliza
- Immunology Section, ARC-Onderstepoort Veterinary Research Institute, Onderstepoort, Republic of South Africa
- Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort, Republic of South Africa
| | - Wouter Van Wyngaardt
- Immunology Section, ARC-Onderstepoort Veterinary Research Institute, Onderstepoort, Republic of South Africa
| | - Dion H. Du Plessis
- Immunology Section, ARC-Onderstepoort Veterinary Research Institute, Onderstepoort, Republic of South Africa
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139
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Somatic hypermutations and isotype restricted exceptionally long CDR3H contribute to antibody diversification in cattle. Vet Immunol Immunopathol 2008; 127:106-13. [PMID: 19012969 DOI: 10.1016/j.vetimm.2008.09.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Revised: 09/10/2008] [Accepted: 09/29/2008] [Indexed: 11/24/2022]
Abstract
Antibody diversification in IgM and IgG antibodies was analyzed in an 18-month old bovine (Bos taurus) suffering from naturally occurring chronic and recurrent infections due to bovine leukocyte adhesion deficiency (BLAD). The BLAD, involving impaired leukocyte beta2 integrin expression on leukocytes, develops due to a single point mutation in conserved region of the CD18 gene resulting in substitution of aspartic acid128 with glycine (D128G). Twenty four VDJCmu and 25 VDJCgamma recombinations from randomly constructed cDNA libraries, originating from peripheral blood lymphocytes, were examined for the variable-region structural characteristics in IgM and IgG antibody isotypes. These analyses led to conclude that: (a) expression of exceptionally long CDR3H is isotype restricted to cattle IgM antibody; (b) VDJ recombinations encoding IgM with exceptionally long CDR3H undergo clonal selection and affinity maturation via somatic mutations similar to conventional antibodies; (c) somatic mutations contribute significantly to both IgM and IgG antibody diversification but significant differences exist in the patterns of 'hot spot' in the FR1, FR3 and CDR1H and, also, position-dependant amino acid diversity; and (d) transition nucleotide substitutions predominate over transversions in both VDJCmu and VDJCgamma recombinations consistent with the evolutionary conservation of somatic mutation machinery. Overall, these studies suggest that both somatic mutations and exceptional CDR3H size generation contribute to IgM and IgG antibody diversification in cattle during the development of immune response to naturally occurring chronic and multiple microbial infections.
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140
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Abstract
Interlocus gene conversion is considered a crucial mechanism for generating novel combinations of polymorphisms in duplicated genes. The importance of gene conversion between duplicated genes has been recognized in the major histocompatibility complex and self-incompatibility genes, which are likely subject to diversifying selection. To theoretically understand the potential role of gene conversion in such situations, forward simulations are performed in various two-locus models. The results show that gene conversion could significantly increase the number of haplotypes when diversifying selection works on both loci. We find that the tract length of gene conversion is an important factor to determine the efficacy of gene conversion: shorter tract lengths can more effectively generate novel haplotypes given the gene conversion rate per site is the same. Similar results are also obtained when one of the duplicated genes is assumed to be a pseudogene. It is suggested that a duplicated gene, even after being silenced, will contribute to increasing the variability in the other locus through gene conversion. Consequently, the fixation probability and longevity of duplicated genes increase under the presence of gene conversion. On the basis of these findings, we propose a new scenario for the preservation of a duplicated gene: when the original donor gene is under diversifying selection, a duplicated copy can be preserved by gene conversion even after it is pseudogenized.
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141
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Abstract
Four types of immunoglobulin (Ig) have been identified in ducks: IgM, a secretory Ig resembling IgM, a 7.8S IgG, and a 5.7S IgG. Structurally and antigenically the 5.7S IgG resembles an F(ab')2 fragment of the 7.8S IgG. When ducks mount serum antibody responses, the sequence of Ig involvement is IgM --> 7.8S IgG --> 5.7S IgG. Although serum Ig levels increase, and antigen-binding Igs can be demonstrated, sera from repeatedly immunized ducks commonly lack secondary antibody activities such as agglutination, precipitation, complement fixation and tissue sensitization. These deficiencies are most likely attributable to the absence of functionally important components of the predominant Ig (5.7S IgG) and/or a possibly unusual steric structure of duck Igs. A related issue concerns production of the two antigenically related IgGs: what are the cellular and molecular events involved, and how are they controlled? Evidence from current molecular genetic studies has confirmed the similarity of the VH, CH1 and CH2 domains of the 7.8S and 5.7S IgGs and shown, by virtue of the existence of separate mature messages for the heavy (H) chains of these molecules, that they are biosynthesized independently. Models for the possibilities that the two H chains are products of one gene or of two genes are presented. Cloning and sequencing the duck H chain gene locus, which is in progress, is providing data supporting the one gene hypothesis. The results obtained from cDNA sequencing also confirm that the duck IgGs are unusual in terms of the anatomy of the hinge region and of the number and location of intra- and inter-chain disulphide bonds, observations which will be of importance for understanding structure/function relationships of these unusual and interesting molecules.
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Affiliation(s)
- D A Higgins
- Department of Pathology, University of Hong Kong, Queen Mary Hospital, Hong Kong
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142
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Abstract
Chicken DT40 cells deficient in the 9-1-1 checkpoint clamp exhibit hypersensitivity to a variety of DNA-damaging agents. Although recent work suggests that, in addition to its role in checkpoint activation, this complex may play a role in homologous recombination and translesion synthesis, the cause of this hypersensitivity has not been studied thoroughly. The immunoglobulin locus of DT40 cells allows monitoring of homologous recombination and translesion synthesis initiated by activation-induced deaminase (AID)-dependent abasic sites. We show that both the RAD9(-/-) and RAD17(-/-) mutants exhibit substantially reduced immunoglobulin gene conversion. However, the level of nontemplated immunoglobulin point mutation increased in these mutants, a finding that is reminiscent of the phenotype resulting from the loss of RAD51 paralogs or Brca2. This suggests that the 9-1-1 complex does not play a central role in translesion synthesis in this context. Despite reduced immunoglobulin gene conversion, the RAD9(-/-) and RAD17(-/-) cells do not exhibit a prominent defect in double-strand break-induced gene conversion or a sensitivity to camptothecin. This suggests that the roles of Rad9 and Rad17 may be confined to a subset of homologous recombination reactions initiated by replication-stalling lesions rather than those associated with double-strand break repair.
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143
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Cohn M. A hypothesis accounting for the paradoxical expression of the D gene segment in the BCR and the TCR. Eur J Immunol 2008; 38:1779-87. [PMID: 18546143 PMCID: PMC2682786 DOI: 10.1002/eji.200738089] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The D gene segment expressed in both the TCR and the BCR has a challenging behavior that begs interpretation. It is incorporated in three reading frames in the rearranged transcription unit but is expressed in antigen-selected cells in a preferred frame. Why was it so important to waste 2/3 of newborn cells? The hypothesis is presented that the D region is framework playing a role in both the TCR and the BCR by determining whether a signal is transmitted to the cell upon interaction with a cognate ligand. This assumption operates in determining haplotype exclusion for the BCR and in regulating the signaling orientation for the TCR. Relevant data as well as a definitive experiment challenging the validity of this hypothesis, are discussed.
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MESH Headings
- Animals
- Antibody Diversity/genetics
- Antibody Diversity/immunology
- Biological Evolution
- Gene Expression
- Gene Rearrangement, alpha-Chain T-Cell Antigen Receptor
- Gene Rearrangement, beta-Chain T-Cell Antigen Receptor
- Genes, T-Cell Receptor alpha
- Genes, T-Cell Receptor beta
- Humans
- Immunoglobulins/genetics
- Immunoglobulins/immunology
- Reading Frames
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
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Affiliation(s)
- Melvin Cohn
- Conceptual Immunology Group, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
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144
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Reddy SK, Hu T, Gudivada R, Staines KA, Wright KE, Vickerstaff L, Kothlow S, Hunt LG, Butter C, Kaspers B, Young JR. The BAFF-Interacting receptors of chickens. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2008; 32:1076-1087. [PMID: 18395254 DOI: 10.1016/j.dci.2008.02.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 02/14/2008] [Accepted: 02/16/2008] [Indexed: 05/26/2023]
Abstract
The TNF superfamily cytokine BAFF has crucial roles in homoeostatic regulation of B cell populations in mammals. Similar effects on peripheral B cells have been reported for chicken as for mammalian BAFF. Unlike mammalian BAFF, chicken BAFF is produced by B cells, implying an autocrine loop and consequent differences in regulation of B cell homoeostasis. Understanding of these mechanisms requires investigation of BAFF-binding receptors in chickens. We identified and characterised chicken receptors BAFFR and TACI, but found that the gene encoding the third BAFF-binding receptor, BCMA, was disrupted, implying differences in mechanisms for maintenance of long-lived antibody responses. A BAFFR-Ig fusion protein expressed in vivo lowered B cell numbers, showing that it was functional under physiological conditions. We found changes in the ratio of BAFFR and TACI mRNAs in the bursa after hatch that may account for the altered requirements for B cell survival at this stage of development.
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Affiliation(s)
- Shalini K Reddy
- Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
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145
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Kothlow S, Morgenroth I, Tregaskes CA, Kaspers B, Young JR. CD40 ligand supports the long-term maintenance and differentiation of chicken B cells in culture. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2008; 32:1015-1026. [PMID: 18374414 DOI: 10.1016/j.dci.2008.01.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 01/25/2008] [Accepted: 01/30/2008] [Indexed: 05/26/2023]
Abstract
TNF family members play crucial roles in mammalian B-cell differentiation and function, many of which have not been demonstrated in other species. To investigate the avian CD40/CD40L system, a chicken CD40 cDNA, obtained by expression screening, was used to raise monoclonal antibodies showing that CD40 was expressed on chicken B cells, monocytes and macrophages, like mammalian CD40. CD40 ligand fusion protein supported the proliferation of B cells in culture for up to 3 weeks, during which they differentiated towards a plasma cell phenotype. CD40L-activated B cells from immunised birds secreted antigen-specific IgM and IgG. These results showed important conserved functions of CD40 and its ligand in mammals and birds. CD40L provides a means for maintenance and differentiation of untransformed chicken B cells in culture, for the first time, allowing new approaches to study of post-bursal B cell biology and host-pathogen interactions with B cell tropic viruses.
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Affiliation(s)
- Sonja Kothlow
- Institute for Animal Physiology, University of Munich, Veterinärstr. 13, 80539 Munich, Germany.
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146
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Lin W, Hashimoto SI, Seo H, Shibata T, Ohta K. Modulation of immunoglobulin gene conversion frequency and distribution by the histone deacetylase HDAC2 in chicken DT40. Genes Cells 2008; 13:255-68. [DOI: 10.1111/j.1365-2443.2008.01166.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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147
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Changes in lymphatic organs of layer chickens following vaccination against Marek’s disease: Histological and stereological analysis. ACTA VET-BEOGRAD 2008. [DOI: 10.2298/avb0801003m] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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148
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Zimmerman AM, Yeo G, Howe K, Maddox BJ, Steiner LA. Immunoglobulin light chain (IgL) genes in zebrafish: Genomic configurations and inversional rearrangements between (V(L)-J(L)-C(L)) gene clusters. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2008; 32:421-34. [PMID: 18022691 PMCID: PMC3014032 DOI: 10.1016/j.dci.2007.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 07/20/2007] [Accepted: 08/12/2007] [Indexed: 05/13/2023]
Abstract
In mammals, Immunoglobulin light chain (IgL) are localized to two chromosomal regions (designated kappa and lambda). Here we report a genome-wide survey of IgL genes in the zebrafish revealing (V(L)-J(L)-C(L)) clusters spanning 5 separate chromosomes. To elucidate IgL loci present in the zebrafish genome assembly (Zv6), conventional sequence similarity searches and a novel scanning approach based on recombination signal sequence (RSS) motifs were applied. RT-PCR with zebrafish cDNA was used to confirm annotations, evaluate VJ-rearrangement possibilities and show that each chromosomal locus is expressed. In contrast to other vertebrates in which IgL exon usage has been studied, inversional rearrangement between (V(L)-J(L)-C(L)) clusters were found. Inter-cluster rearrangements may convey a selective advantage for editing self-reactive receptors and poise zebrafish by virtue of their extensive numbers of V(L), J(L) and C(L) to have greater potential for immunoglobulin gene shuffling than traditionally studied mice and human models.
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149
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Abi-Ghanem D, Waghela SD, Caldwell DJ, Danforth HD, Berghman LR. Phage display selection and characterization of single-chain recombinant antibodies against Eimeria tenella sporozoites. Vet Immunol Immunopathol 2008; 121:58-67. [PMID: 17897723 DOI: 10.1016/j.vetimm.2007.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 06/15/2007] [Accepted: 08/02/2007] [Indexed: 11/28/2022]
Abstract
A single-chain antibody library against Eimeria tenella sporozoites was constructed by phage display. Antibody-displaying phage was selected in five panning rounds against cryopreserved E. tenella sporozoites. A 1000-fold increase in phage output and a 3000-fold enrichment were obtained after three rounds of panning, as the binding clones became the dominant population in the library. Ten clones were randomly selected from the last selection round, and their nucleotide sequences were aligned and compared to chicken germ-line sequences. Analysis of the light chain variable regions revealed possible donor pseudogenes which act as donors in gene conversion events, and contribute to the diversification of the V(L) immune repertoire. Possible somatic hypermutation events, a consequence of affinity maturation, were also identified. Soluble antibody was produced in a non-suppressor E. coli strain, purified by nickel affinity chromatography, and characterized by immunoblotting. In an immunofluorescence assay, this recombinant antibody showed specific binding to E. tenella sporozoites.
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Affiliation(s)
- Daad Abi-Ghanem
- Department of Poultry Science, Texas A&M University, 2472 TAMU, College Station, TX 77843-2472, United States
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150
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Cummings WJ, Yabuki M, Ordinario EC, Bednarski DW, Quay S, Maizels N. Chromatin structure regulates gene conversion. PLoS Biol 2007; 5:e246. [PMID: 17880262 PMCID: PMC1976632 DOI: 10.1371/journal.pbio.0050246] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Accepted: 07/17/2007] [Indexed: 12/29/2022] Open
Abstract
Homology-directed repair is a powerful mechanism for maintaining and altering genomic structure. We asked how chromatin structure contributes to the use of homologous sequences as donors for repair using the chicken B cell line DT40 as a model. In DT40, immunoglobulin genes undergo regulated sequence diversification by gene conversion templated by pseudogene donors. We found that the immunoglobulin Vλ pseudogene array is characterized by histone modifications associated with active chromatin. We directly demonstrated the importance of chromatin structure for gene conversion, using a regulatable experimental system in which the heterochromatin protein HP1 (Drosophila melanogaster Su[var]205), expressed as a fusion to Escherichia coli lactose repressor, is tethered to polymerized lactose operators integrated within the pseudo-Vλ donor array. Tethered HP1 diminished histone acetylation within the pseudo-Vλ array, and altered the outcome of Vλ diversification, so that nontemplated mutations rather than templated mutations predominated. Thus, chromatin structure regulates homology-directed repair. These results suggest that histone modifications may contribute to maintaining genomic stability by preventing recombination between repetitive sequences. Homologous recombination promotes genetic exchange between regions containing identical or highly related sequences. This is useful in repairing damaged DNA, or in reassorting genes in meiosis, but uncontrolled homologous recombination can create genomic instability. Chromosomes are made up of a complex of DNA and protein, called chromatin. DNA within chromatin is packed tightly in order to fit the entire genome inside a cell; but chromatin structure may become relaxed to allow access to enzymes that regulate gene expression, transcribe genes into mesenger RNA, or carry out gene replication. We asked if chromatin packing regulates homologous recombination. To do this, we tethered a factor associated with compact chromatin, called HP1, adjacent to an immunoglobulin gene locus at which homologous recombination occurs constitutively, in order to produce a diverse repertoire of antibodies. We found that the compact, repressive chromatin structure produced by HP1 prevents homologous recombination. This finding suggests that regulated changes in chromatin structure may contribute to maintaining genomic stability by preventing recombination between repetitive sequences. Much of the chromosome is tightly packed (heterochromatic) and not transcribed. Here, the authors show that tight packing has another effect: it prevents recombination between homologous sequences.
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Affiliation(s)
- W. Jason Cummings
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Munehisa Yabuki
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Ellen C Ordinario
- Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - David W Bednarski
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Simon Quay
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Nancy Maizels
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington, United States of America
- * To whom correspondence should be addressed. E-mail:
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