			Home About us Contact

Peptide Antigen (peptide + antigen)

Distribution by Scientific Domains

Medical Sciences	58%
Chemistry	33%

Selected Abstracts

T cell anergy and costimulation

IMMUNOLOGICAL REVIEWS, Issue 1 2003
Leonard J. Appleman
Summary:, T lymphocytes play a key role in immunity by distinguishing self from nonself peptide antigens and regulating both the cellular and humoral arms of the immune system. Acquired, antigen-specific unresponsiveness is an important mechanism by which T cell responses to antigen are regulated in vivo. Clonal anergy is the term that describes T cell unresponsiveness at the cellular level. Anergic T cells do not proliferate or secrete interleukin (IL)-2 in response to appropriate antigenic stimulation. However, anergic T cells express the IL-2 receptor, and anergy can be broken by exogenous IL-2. Anergy can be induced by submitogenic exposure to peptide antigen in the absence of a costimulatory signal provided by soluble cytokines or by interactions between costimulatory receptors on T cells and counter-receptors on antigen-presenting cells. The molecular events that mediate the induction and maintenance of T cell anergy are the focus of this review. The molecular consequences of CD28,B7 interaction are discussed as a model for the costimulatory signal that leads to T cell activation rather than the induction of anergy. [source]

PD-1 signalling in CD4+ T cells restrains their clonal expansion to an immunogenic stimulus, but is not critically required for peptide-induced tolerance

IMMUNOLOGY, Issue 1 2010
Joanne E. Konkel
Summary The ultimate outcome of T-cell recognition of peptide,major histocompatibility complex (MHC) complexes is determined by the molecular context in which antigen presentation is provided. The paradigm is that, after exposure to peptides presented by steady-state dendritic cells (DCs), inhibitory signals dominate, leading to the deletion and/or functional inactivation of antigen-reactive T cells. This has been utilized in a variety of models providing peptide antigen in soluble form in the absence of adjuvant. A co-inhibitory molecule of considerable current interest is PD-1. Here we show that there is the opportunity for the PD-1/PD-L1 interaction to function in inhibiting the T-cell response during tolerance induction. Using traceable CD4+ T-cell receptor (TCR) transgenic cells, together with a blocking antibody to disrupt PD-1 signalling, we explored the roles of PD-1 in the induction of tolerance versus a productive immune response. Intact PD-1 signalling played a role in limiting the extent of CD4+ T-cell accumulation in response to an immunogenic stimulus. However, PD-1 signalling was not required for either the induction, or the maintenance, of peptide-induced tolerance; a conclusion underlined by successful tolerance induction in TCR transgenic cells genetically deficient for PD-1. These observations contrast with the reported requirement for PD-1 signals in CD8+ T-cell tolerance. [source]

Serological response to hepatitis E virus genotype 3 infection: IgG quantitation, avidity, and IgM response

JOURNAL OF MEDICAL VIROLOGY, Issue 1 2008
R. Bendall
Abstract Sequential sera were collected from 18 acute cases of UK-acquired hepatitis E. The virus strains in all cases were of genotype 3. The IgM and IgG response to acute infection were documented over time using EIA kits based on a peptide antigen, pE2, which is derived from a genotype 1 strain of hepatitis E virus (HEV). Ninety-five percentage of acute sera were IgM positive; after 6 months or more only 12% remained positive. The kit was adapted to quantify the IgG response (in WHO U/ml) and to determine antibody avidity. Following acute infection, anti-HEV IgG concentrations rose between 6.9- and 90-fold. IgG avidity was low (<25%) in most acute sera. After 6 months IgG avidity was greater than 50% in all cases. One patient with a poor IgM response and high avidity antibody in acute sera may have had a second HEV infection. Taken together, these results confirm that the pE2-based EIA kits are suitable for diagnosing acute HEV genotype 3 infection. With simple modifications the IgG kit can measure anti-HEV concentration and avidity, which can be used to confirm acute infection. J. Med. Virol. 80:95,101, 2008. © 2007 Wiley-Liss, Inc. [source]

Characterization of an Antibody to the Human Melatonin mt1 Receptor

JOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2001
L. M. Williams
Abstract Melatonin acts via high affinity, G-protein coupled, seven transmembrane domain receptors. To precisely localize these receptors, antibodies were raised in chickens against a 15 amino acid fragment at the intracellular C -terminal region of the human melatonin receptor subtype mt1 (DSSNDVADRVKWKPS, mt1338,352). A chimeric form of the receptor with a hydrophilic Flag peptide (DYKDDDDK) in sequence with the extracellular N -terminus (Flag-mt1) was generated by polymerase chain reaction and expressed in mammalian cell lines. An IgY antibody (Y31), which gave high antibody titres by enzyme-linked immunosorbent assay, was used to localize Flag-mt1 in stably transfected cells by immunofluoresence. Flag-mt1 localization with Y31 was identical to that obtained with the M5 antibody directed against the Flag epitope and was mainly localized to the Golgi apparatus with some staining at the cell surface. No staining was seen in untransfected cells with either antibody. Y31 staining was abolished using antibody preabsorbed with peptide antigen. Y31 immunofluorescence in fetal human kidney sections was restricted to nephrogenic regions and matched that of 2-(125I)iodomelatonin binding and mt1 gene expression by in situ hybridization. Y31 was used to immunoprecipitate biotinylated membrane proteins from Flag-mt1 stably transfected and untransfected CHO cells. Western blotting of immunoprecipitated proteins revealed two major bands specific to stably transfected cells, one at 63 kDa and one at 86 kDa. The first band almost certainly corresponds to the glycosylated form of Flag-mt1 and the second band to receptor dimers. Thus, Y31 antibody is suitable for use in detecting the human mt1 receptor subtype in tissues and in transfected cells. [source]

Improving the affinity of antigens for mutated antibodies by use of statistical molecular design

JOURNAL OF PEPTIDE SCIENCE, Issue 7 2008
Ilona Mandrika
Abstract We demonstrate the use of statistical molecular design (SMD) in the selection of peptide libraries aimed to systematically investigate antigen-antibody binding spaces. Earlier, we derived two novel antibodies by mutating the complementarity-determining region of the anti-p24 (HIV-1) single chain Fv antibody, CB4-1 that had lost their affinity for a p24 epitope-homologous peptide by 8- and 60-fold. The present study was devoted to explore how peptide libraries can be designed under experimental design criteria for effective screening of peptide antigens. Several small peptide,antigen libraries were selected using SMD principles and their activities were evaluated by their binding to SPOT-synthesized peptide membranes and by fluorescence polarization (FP). The approach was able to reveal the most critical residues required for antigen binding, and finally to increase the binding activity by proper modifications of amino acids in the peptide antigen. A model of the active peptide binding pocket formed by the mutated scFv and the antigen was compatible with the information gained from the experimental data. Our results suggest that SMD approaches can be used to explore peptide antigen features essential for their interactions with antibodies. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source]

Relative distribution of three major lactate transporters in frozen human tissues and their localization in unfixed skeletal muscle

MUSCLE AND NERVE, Issue 1 2002
William N. Fishbein MD
Abstract We have prepared affinity-purified rabbit polyclonal antibodies to the near-C-terminal peptides of human monocarboxylate transporters (MCTs) 1, 2, and 4 coupled to keyhole limpet hemocyanin. Each antiserum reacted only with its specific peptide antigen and gave a distinct molecular weight band (blocked by preincubation with antigen) after chemiluminescence reaction on Western blots from sodium dodecyl sulfate,polyacrylamide gel electrophoresis (SDS-PAGE) of tissue membrane proteins. Densitometry showed distinctive expression patterns for each MCT in a panel of 15 frozen human tissues, with the distribution of MCT1 ,L:MCT2>MCT4. Fluorescence microscopy of unfixed skeletal muscle using fluorescein-conjugated secondary antibody was correlated with reverse adenosine triphosphatase (ATPase) stained sequential sections to identify fiber-type localization. MCT1 expression was high in the sarcolemma of type 1 fibers, modest to low in type 2a fibers, and almost absent in type 2b fibers. In contrast, MCT4 expression was low to absent in the membrane of most type 1 fibers, but high in most 2a and in all 2b fibers, favoring the view that their high lactate levels during work may be channeled in part to neighboring type 1 (and perhaps 2a) fibers for oxidation, thereby delaying fatigue. MCT2 expression was limited to the sarcolemma of a type 1 fiber subset, which varied from <5 to 40%, depending on the specific muscle under study. Quantitative chemiluminescent densitometry of 10 muscle biopsies for their MCT2 and MCT4 content, each normalized to MCT1, confirmed the unique variation of MCT2 expression with biopsy site. The application of these antibodies should add to the understanding of motor unit physiology, and may contribute to the muscle-biopsy assessment of low-level denervation. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 101,112, 2002 [source]

Quantitative specificity-based display library screening identifies determinants of antibody-epitope binding specificity,

PROTEIN SCIENCE, Issue 9 2009
Sejal S. Hall
Abstract Despite the critical importance of molecular specificity in bimolecular systems, in vitro display technologies have been applied extensively for affinity maturation of peptides and antibodies without explicitly measuring the specificity of the desired interaction. We devised a general strategy to measure, screen, and evolve specificity of protein ligand interactions analogous to widely used affinity maturation strategies. The specificity of binding to target and nontarget antibodies labeled with spectrally distinct fluorophores was measured simultaneously in protein mixtures via multiparameter flow cytometry, thereby enabling screening for high target antibody specificity. Isolated antibody specific ligands exhibited varying specificity, revealing critical amino acid determinants for target recognition and nontarget avoidance in complex mixtures. Molecular specificity in the mixture was further enhanced by quantitative directed evolution, yielding a family of epitopes exhibiting improved specificities equivalent, or superior to, the native peptide antigen to which the antibody was raised. Specificity screening simultaneously favored affinity, yielding ligands with three-fold improved affinity relative to the parent epitope. Quantitative specificity screening will be useful to screen, evolve, and characterize the specificity of protein and peptide interactions for molecular recognition applications. [source]

Thymic stromal cells and positive selection

APMIS, Issue 7-8 2001
Ann R. Chidgey
The intrathymic differentiation events leading to the development and export of mature T cells tolerant to self yet capable of responding to foreign peptide antigen in the context of self-MHC are clearly both dynamic and complex. The changing phenotype of the developing thymocyte as it migrates through and interacts with the heterogeneous thymic microenvironment and the intracellular signalling events associated with such interactions are being extensively studied, yet many aspects remain poorly defined, such as the precise relationship between stromal cells and thymic selection. Positive and negative selection are crucial events in the development of T cells, leading to a diverse yet non-autoreactive immune system. A breakdown in either of these processes could lead to either a reduced T cell repertoire or the escape into the periphery of autoreactive T cells , both clearly having deleterious consequences for the health of the individual. This review aims to summarise the current status of research in thymic positive selection with emphasis on the role of different cell types and peptides. [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]

N-terminal destruction signals lead to rapid degradation of the major histocompatibility complex class II transactivator CIITA

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2003
Felix Schnappauf
Abstract Major histocompatibility complex (MHC) class II molecules play an essential role for the cellular immune response by presenting peptide antigens to CD4+ T cells. MHC class II molecules and genes show a highly complex expression pattern, which is orchestrated through a master regulatory factor, called CIITA (class II transactivator). CIITA controls MHC class II expression not only qualitatively, but also quantitatively, and has therefore a direct influence on the CD4 T cell-dependent immune response. CIITA is itself tightly regulated not only on the transcriptional level, but as we show here also on the protein level. CIITA is subjected to a very rapid protein turnover and shows a half-life of about 30,min. Inhibition of degradation by proteasome inhibitors and the identification of ubiquitylated CIITA intermediates indicate that the degradation of CIITA is mediated by the ubiquitin-proteasome system. We identified two regions mediating degradation within the N-terminal domain of CIITA. N-terminal fusions or deletions stabilized CIITA, indicating that the N termini contribute to degradation. Several non-functional CIITA mutants are partially stabilized, but we provide evidence that transcriptional activity of CIITA is not directly linked to degradation. [source]