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Cognate Antigen (cognate + antigen)

Distribution by Scientific Domains

Medical Sciences	69%
Life Sciences	15%

Selected Abstracts

Identification of Evolutionary Conserved Mouse Sperm Surface Antigens by Human Antisperm Antibodies (ASA) from Infertile Patients

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 5 2006
Agnieszka Paradowska
Problem The presence of antisperm antibodies (ASA) in semen may impair sperm function leading to immunological infertility. The aim of the study was to identify the evolutionary conserved antigens on mouse sperm surface that react with human ASA in order to study the mechanism of autoimmune infertility. Methods of study The binding of human ASA to mouse sperm was investigated by means of indirect immunofluorescence. 2D-electrophoresis was applied to separate the biotin-labelled mouse membrane proteins using isoelectric focusing followed by polyacrylamide gel electrophoresis. Cognate antigens of ASA from seminal plasma of infertile patients were analysed by Western blotting. Performing avidin-blots it was detected which of the proteins recognized were sperm surface proteins. The spots of interest were analysed by means of mass spectrometry. Results ASA bound most frequently (36%) to the post-acrosomal region and to the midpiece of mouse spermatozoa. About 30% of ASA recognized apo lactate dehydrogenase (LDHC4) as a cognate antigen, 30% voltage-dependent anion channel (VDAC2). ASA of 20% bound to outer dense fibre protein and 20% of samples recognized glutathione S-transferase mu5. Conclusions Human ASA bound to specific cognate antigens of mouse spermatozoa, offering the possibility to study their functional relevance in the mouse model. [source]

Decreased specific CD8+ T,cell cross-reactivity of antigen recognition following vaccination with Melan-A peptide

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2006
Victor Appay
Abstract The aim of T,cell vaccines is the expansion of antigen-specific T,cells able to confer immune protection against pathogens or tumors. Although increase in absolute cell numbers, effector functions and TCR repertoire of vaccine-induced T,cells are often evaluated, their reactivity for the cognate antigen versus their cross-reactive potential is rarely considered. In fact, little information is available regarding the influence of vaccines on T,cell fine specificity of antigen recognition despite the impact that this feature may have in protective immunity. To shed light on the cross-reactive potential of vaccine-induced cells, we analyzed the reactivity of CD8+ T,cells following vaccination of HLA-A2+ melanoma patients with Melan-A peptide, incomplete Freund's adjuvant and CpG-oligodeoxynucleotide adjuvant, which was shown to induce strong expansion of Melan-A-reactive CD8+ T,cells in vivo. A collection of predicted Melan-A cross-reactive peptides, identified from a combinatorial peptide library, was used to probe functional antigen recognition of PBMC ex vivo and Melan-A-reactive CD8+ T,cell clones. While Melan-A-reactive CD8+ T,cells prior to vaccination are usually constituted of widely cross-reactive naive cells, we show that peptide vaccination resulted in expansion of memory T,cells displaying a reactivity predominantly restricted to the antigen of interest. Importantly, these cells are tumor-reactive. [source]

Immediate antigen-specific effector functions byTCR-transgenic CD8+ NKT cells

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2006
Gerhard Wingender
Abstract Only recently have natural antigens for CD1d-dependent, invariant V,14+ natural killer T (iNKT) cells been identified. Similar data for CD1d-independent and CD8+ NKT cell populations are still missing. Here, we show that the MHC class,I-restricted CD8+ TCR-transgenic mouse lines OT-I, P14 and H-Y contain a significant proportion of transgenic CD8+ NK1.1+ T,cells. In liver, most of NK1.1+ T,cells express CD8,, homodimers. Transgenic NKT cells did not bind invariant V,14-to-J,18 TCR rearrangement (V,14i)-specific CD1d/,-galactosylceramide tetramers and the frequency of iNKT cells was severely reduced. The activated cell surface phenotype and the distribution of transgenic NKT cells in vivo were similar to that reported for iNKT cells. The OT-I and P14 CD8+ NKT cells recognized their cognate antigen in the context of H2-Kb and produced cytokines shortly after TCR stimulation. Importantly, transgenic NKT cells exerted immediate antigen-specific cytotoxicity in vitro and in vivo. Our results demonstrate the presence of transgenic CD8+ NKT cells in MHC class,I-restricted TCR-transgenic animals, which are endowed with rapid antigen-specific effector functions. These data imply that experiments studying naive T,cell function in TCR-transgenic animals should be interpreted with caution, and that such animals could be utilized for studying CD8+ NKT cell function in an antigen-specific manner. [source]

CpG ODN enhance antigen-specific NKT cell activation via plasmacytoid dendritic cells

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2005
Anja Marschner
Abstract Human V,24+ V,11+ natural killer T cells (NKT cells) are "natural memory" T cells that detect glycolipid antigens such as ,-galactosylceramide (,-GalCer) presented on CD1d. In the present study we found that highly purified V,24+ NKT cells lack TLR9 mRNA, and thus are not sensitive towards stimulation with CpG oligodeoxynucleotides (ODN). Within PBMC, however, CpG ODN synergistically activated NKT cells stimulated with their cognate antigen ,-GalCer. Depletion of plasmacytoid dendritic cells (PDC) or myeloid dendritic cells (MDC) revealed that both DC subsets were necessary for the synergistic activation of NKT cells by ,-GalCer and CpG ODN. While PDC were responsible for the stimulation of NKT cells with CpG ODN, MDC but not PDC presented ,-GalCer via CD1d. Partial activation of NKT cells was mediated by PDC-derived IFN-,, whereas full activation of NKT cells as indicated by IFN,, production required cell-to-cell contact of PDC and NKT cells in addition to IFN-,; OX40 was involved in this interaction. We conclude that CpG-activated PDC enhance ,-GalCer-specific NKT cell activation, and bias activated NKT cells towards a Th1 phenotype. Our results lead to a novel concept of PDC function: to regulate effector activity of antigen-stimulated T cells in a cell contact-dependent manner without the need of simultaneous presentation of the cognate T cell antigen. [source]

Secretion of proteins with dimerization capacity by the haemolysin type I transport system of Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 4 2004
Sofía Fraile
Summary The tolerance of the haemolysin transport system (Hly) for exporting dimeric protein substrates to the supernatants of Escherichia coli cultures was examined. A strong dimerization domain (i.e. an amphipathic ,-helix capable of forming a leucine zipper in the yeast transcription factor GCN4) was inserted into an epitope-tagged version of the 23 kDa C-terminal secretion signal of haemolysin (EHlyA). The zipper-containing polypeptide (ZEHlyA) was effectively secreted by E. coli cells carrying the HlyBD transporter and accumulated in the culture media as a stable dimer as determined by gel filtration chromatography. In vivo protein cross-linking experiments and coexpression with a secretion-deficient derivative of ZEHlyA indicated that leucine zipper-dependent dimerization occurs following secretion. To test whether dimerization allows the correct folding of the secreted polypeptide, immunoglobulin VHH -domains obtained from camel antibodies were fused to EHlyA and ZEHlyA. Functional dimerization of the ZEHlyA hybrid was anticipated to increase the apparent binding affinity (i.e. avidity) of the VHH moiety, thus becoming an excellent reporter of correct protein folding and dimerization. Both VHH -EHlyA and VHH -ZEHlyA hybrids were quantitatively secreted and found in the extracellular medium as active monomers and dimers respectively. When compared with their monomeric counterparts, the dimeric VHH -ZEHlyA molecules showed superior binding properties to their cognate antigen, with a 10-fold increase in their avidity. These data reveal a non-anticipated permissiveness of the Hly type I transport machinery for the secretion of substrates with dimerization capacity. [source]

Identification of Evolutionary Conserved Mouse Sperm Surface Antigens by Human Antisperm Antibodies (ASA) from Infertile Patients

Localizing central nervous system immune surveillance: Meningeal antigen-presenting cells activate T cells during experimental autoimmune encephalomyelitis

ANNALS OF NEUROLOGY, Issue 4 2009
Pia Kivisäkk MD
Objective The onset of neurological signs in experimental autoimmune encephalomyelitis is tightly associated with infiltration and reactivation of T cells in the central nervous system. The anatomic localization of the initial T cell-antigen-presenting cell (APC) interactions leading to reactivation of T cells in the central nervous system is, however, still unclear. We hypothesized that activated CD4+ T cells gain direct access to the subarachnoid space and become reactivated on encounter with cognate antigen in this compartment. Methods C57Bl/6 mice were immunized with MOG35-55, and interactions between CD4+ T cells and major histocompatibility class II+ APCs in the subarachnoid space were investigated using flow cytometry, confocal microscopy of leptomeningeal whole-mount preparations, time-lapse microscopy of leptomeningeal explants, and in vitro proliferation assays. Results CD4+ T cells, polarized to produce Th1/Th17 cytokines, accumulated in the subarachnoid space early during the course of experimental autoimmune encephalomyelitis, before CD4+ T cells were detected in the spinal cord parenchyma. At this time point, leptomeningeal but not parenchymal CD4+ T cells incorporated bromodeoxyuridine, indicating local proliferation of CD4+ T cells in the subarachnoid space. Time-lapse microscopy indicated that these CD4+ T cells actively scanned the tissue and interacted with local major histocompatibility class II+ APCs, resulting in long-lasting interactions between CD4+ T cells and major histocompatibility class II+ APCs, suggestive of immunological synapses. Interpretation These results support the concept that immune surveillance of the central nervous system involves the subarachnoid space and indicate that the leptomeninges play an important role in experimental autoimmune encephalomyelitis initiation. Ann Neurol 2009;65:457,469 [source]

Crystallization and preliminary X-ray diffraction analysis of the complex of a human anti-ephrin type-A receptor 2 antibody fragment and its cognate antigen

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010
Vaheh Oganesyan
The recombinant N-terminal domain of human ephrin type-A receptor 2 (rEphA2) has been crystallized in complex with the recombinantly produced Fab fragment of a fully human antibody (1C1; IgG1/,). These are the first reported crystals of an ephrin receptor bound to an antibody. The orthorhombic crystals belonged to space group C2221 (the 00l reflections obey the l = 2n rule), with unit-cell parameters a = 78.93, b = 120.79, c = 286.20,Å. The diffraction of the crystals extended to 2.0,Å resolution. However, only data to 2.55,Å resolution were considered to be useful owing to spot overlap caused by the long unit-cell parameter. The asymmetric unit is most likely to contain two 1C1 Fab,rEphA2 complexes. This corresponds to a crystal volume per protein weight (VM) of 2.4,Å3,Da,1 and a solvent content of 49.5%. The three-dimensional structure of this complex will shed light on the molecular basis of 1C1 specificity. This will also contribute to a better understanding of the mechanism of action of this antibody, the current evaluation of which as an antibody,drug conjugate in cancer therapy makes it a particularly interesting case study. [source]

Crystallization and preliminary X-ray crystallographic characterization of a public CMV-specific TCR in complex with its cognate antigen

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009
Jean-Baptiste Reiser
The T-cell response to human cytomegalovirus is characterized by a dramatic reduction of clonal diversity in patients undergoing chronic inflammation or immunodepression. In order to check whether all the selected high-avidity T-cell clones recognize the immunodominant pp65 peptide antigen pp65495,503 (NLVPMVATV) presented by the major histocompatibility complex (MHC) molecule HLA-A2 in a similar manner, several public high-affinity T-cell receptors (TCRs) specific for the pp65495,503,HLA-A2 complex have been investigated. Expression, purification and crystallization were performed and preliminary crystallographic data were collected to 4.7,Å resolution for the RA15 TCR in complex with the pp65495,503,HLA-A2 complex. Comparison of the RA15,pp65495,503,HLA-A2 complex molecular-replacement solution with the structure of another high-affinity pp65495,503,HLA-A2-specific TCR, RA14, shows a shared docking mode, indicating that the clonal focusing could be accompanied by the selection of a most favoured peptide-readout mode. However, the position of the RA15 V, domain is significantly shifted, suggesting a different interatomic interaction network. [source]

Selection and growth regulation of genetically modified cells with hapten-specific antibody/receptor tyrosine kinase chimera

BIOTECHNOLOGY PROGRESS, Issue 4 2009
Kento Tanaka
Abstract Although receptor tyrosine kinases (RTKs) play a pivotal role in the development and maintaining the homeostasis of the body, overexpression or mutation of RTKs often induces tumorigenesis or metastasis. To mimic the function of RTKs, we developed two fusion receptors consisting of anti-fluorescein antibody single-chain Fv, extracellular D2 domain of erythropoietin receptor and transmembrane/intracellular domains of epidermal growth factor receptor or c-fms based on previously constructed antibody/cytokine receptor chimeras. The expression of these chimeric receptors in the hematopoietic cell line Ba/F3 and non-hematopoietic cell line NIH/3T3 resulted in the activation of receptors themselves, downstream signaling molecules and cell proliferation in response to fluorescein-conjugated BSA, leading to selective expansion of transduced cells up to almost 100%. These results indicate that the cognate antigen could activate the chimeric receptors even though the wild-type extracellular domains were switched to the antibody fragment. This is the first study to show that our antigen-mediated genetically modified cell amplification (AMEGA) system could be applied to non-hematopoietic cells by utilizing antibody/RTK chimeras. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

TLR9 stimulation drives naïve B cells to proliferate and to attain enhanced antigen presenting function

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2007
Wei Jiang
Abstract Mechanisms that regulate naïve B cell proliferation and function are incompletely defined. In this study, we test the hypothesis that naïve B cell expansion, survival and ability to present antigen to T,lymphocytes can be directly modulated by Toll-like receptor (TLR) agonists. In the absence of B cell receptor stimulation, CpG oligonucleotide, a TLR9 agonist, was particularly efficient in inducing naïve B cell proliferation and survival. Although the expanded naïve B cells did not mature into CD27+ or IgG+ memory B cells, these cells did differentiate into IgM-secreting cells with increased surface expression of HLA-DR, CD40 and CD80. This was associated with an increased potential for these B cells to activate allogeneic T cells. We propose that the activation and expansion of naïve B cells induced by TLR9 agonists could enhance the potential of these cells to interact with cognate antigens and facilitate cell-mediated immune responses. [source]

Identification of Evolutionary Conserved Mouse Sperm Surface Antigens by Human Antisperm Antibodies (ASA) from Infertile Patients

Anti,citrullinated protein antibodies bind surface-expressed citrullinated Grp78 on monocyte/macrophages and stimulate tumor necrosis factor , production

ARTHRITIS & RHEUMATISM, Issue 5 2010
Ming-Chi Lu
Objective Anti,citrullinated protein antibodies (ACPAs), which are the most specific autoantibody marker in patients with rheumatoid arthritis (RA), correlate with disease activity; however, the role of ACPAs in RA pathogenesis has not been elucidated. We hypothesized that ACPAs may directly stimulate mononuclear cells to produce inflammatory cytokines. Thus, we identified cognate antigens of ACPAs on monocyte/macrophages and examined their immunopathologic roles in the pathogenesis of RA. Methods ACPAs were purified from pooled ACPA-positive RA sera by cyclic citrullinated peptide,conjugated affinity column. After coculture of U937 cells with ACPAs, the tumor necrosis factor , (TNF,) production and NF-,B DNA binding activity of the cells were measured by enzyme-linked immunosorbent assay. The cognate antigens of ACPAs on the U937 cell surface were probed by ACPAs, and the reactive bands were examined via proteomic analysis. Results ACPAs specifically enhanced TNF, production and increased the DNA-binding activity of NF-,B in U937 cells. Proteomic analysis revealed that Grp78 protein (72 kd) was one of the cognate antigens of ACPAs. The truncated form of cell surface,expressed Grp78 (55 kd) on U937 cells contained citrulline capable of binding with ACPAs. After citrullination, glutathione S-transferase,tagged recombinant Grp78 (97.52 kd) became a 72-kd fragment and bound with ACPAs. ACPAs also bound to human monocytes and lymphocytes to promote TNF, production. Conclusion We clearly demonstrated that ACPAs enhance NF-,B activity and TNF, production in monocyte/macrophages via binding to surface-expressed citrullinated Grp78. [source]