bluuebunny/crossref_metadata_2025_split huggingface dataset:
Presentation of an exogenous antigen by major histocompatibility complex class I molecules
Authors: Ulmer Jeffrey B. , Donnelly John J. , Liu Margaret A. 
Published: March 2007

AbstractCytotoxic T lymphocytes (CTL) generally recognize peptides derived from endogenously expressed proteins in association with nascent major histocompatibility complex (MHC) class I molecules. In contrast, peptides derived from exogenous proteins associate with MHC class II following endocytosis to an endosomal compartment. However, we have recently demonstrated that exogenous fusion proteins consisting of the binding and translocating domains of Pseudomonas exotoxin (PE) fused with CTL epitopes derived from either influenza matrix protein (PEMa) or nucleoprotein are internalized, processed, targeted to and presented by MHC class I (Donnelly et al. 1993, Proc. Natl. Acad. Sci. USA 1993. 90: 3530). PE is known to be internalized, processed in endosomes, and translocated to the cytosol during intoxication of cells. However, our present studies demonstrate that, unlike PE, PEMa does not require translocation to the cytosol to exert its effect. First, two inhibitors of PE toxicity that exert their effects at steps subsequent to endosomal processing had no effect on the sensitization of target cells for CTL‐mediated lysis by PEMa. NH4Cl, which inhibits PE by raising endosomal pH, and brefeldin A, which inhibits PE by disrupting the Golgi complex, did not inhibit sensitization of targets cells by PEMa. Second, PEMa was capable of sensitizing for lysis T2 mutant cells, which are defective in transport of peptides from the cytosol to the lumen of the endoplasmic reticulum for presentation by MHC class I. These results suggest that PEMa is proteolytically processed in endosomes, and association with MHC class I does not require nascent MHC molecules. Such a process may involve internalized MHC class I, and subsequent expression of the peptide‐MHC complexes on the cell surface would then lead to recognition by CTL.
Characterization of avian natural killer cells and their intracellular CD3 protein complex
Authors: Göbel Thomas W. F. , Chen Chen‐Lo H. , Shrimpf Jane , Grossi Carlo E. , Bernot Alain , Bucy R. Pat , Auffray Charles , Cooper Max D. 
Published: March 2007

AbstractNatural killer (NK) cell activity appears to be conserved throughout vertebrate development but NK cells have only been well characterized in mammals. Candidate NK cells have been identified in the chicken as cytoplasmic CD3+ and surface T cell receptor (TCR)/CD3– (TCRO) lymphocytes that often express CD8. The fact that the TCRO cells are abundant in the embryonic spleen before T cells enter this organ allowed us to cultivate the embryonic TCRO cells using growth factors derived from activated adult lymphocytes. These TCRO cells were cytotoxic for an NK target cell line. They expressed cell surface CD8, a putative interleukin‐2 receptor, CD45 and a receptor for IgG, but did not express CD4, major histocompatibility complex class II or immunoglobulin. Biochemical analysis of the cytoplasmic CD3 antigen revealed two of the three CD3 γ, δ and ϵ homologues, and RNA transcripts for the third. The CD3 monoclonal antibody also precipitated a 32‐kDa dimer that may represent a heterodimer of different CD3 constituents. TCR α and β gene transcripts were not detected in the TCRO cells. These results indicate that the avian TCRO cell is the mammalian NK cell homologue. The shared evolutionary features of T cells and NK cells in birds and mammals support the idea that they derive from a common progenitor.
CD4‐positive/heat‐stable antigen‐positive thymocytes cause graft‐versus‐host disease across non‐major histocompatibility complex incompatibilities
Authors: Charlton Brett , Meltzer Joseph , Fathman C. Garrison 
Published: March 2007

AbstractSingle‐positive thymocytes are the immediate precursors of peripheral recent thymic emigrants (RTE) which develop into mature peripheral T cells. The functional ability of RTE is unclear but their state of differentiation may be relevant to the development of tolerance to peripheral “self” antigens. Since RTE are difficult to analyze, precursor CD4+/8− thymocytes were assessed in a model in vivo to determine their functional capability and their susceptibility to tolerance induction. The ability of both heat‐stable antigen‐positive (HSA+) (immature) and HSA− (mature) single‐positive thymocytes to cause graft‐versus‐host disease (GVHD) across non‐major histocompatibility complex differences was examined. Both HSA− and HSA+ CD4+/8− thymocytes from C3H mice caused lethal GVHD in AKR recipients as did CD4+ peripheral T cells in controls. Further, neonatal C3H thymocytes also caused lethal GVHD in AKR recipients. Since CD4+/8− thymocytes are the precursors of RTE, these results suggest that RTE are not susceptible to tolerance induction to “minor” antigens and may have a normal immune function in vivo. This would suggest that peripheral tolerance may be dependent upon the manner of antigen presentation rather than T cell maturity.
Anchored polymerase chain reaction based analysis of the Vβ repertoire in the non‐obese diabetic (NOD) mouse
Authors: Sarukhanu Adelaida , Gombert Jean‐Marc , Olivi Martine , Bach Jean‐François , Carnaud Claude , Garchon Henri‐Jean 
Published: March 2007

AbstractWe have performed extensive analyses of T cell receptor Vβ usage in the thymus, the spleen and the infiltrated islets of preclinical non‐obese diabetic (NOD) mice. A semiquantitative anchored polymerase chain reaction (An‐PCR) protocol has been developed for this purpose. The validity of the method has been first assessed by antibody staining with a panel of anti‐Vβ monoclonal antibodies (mAb). The results obtained by An‐PCR are accurate, reproducible, and in good agreement with cell surface protein staining. A strict comparison between thymus and spleen repertoires reveals no major Vβ‐specific deletion except the already reported Vβ3 deletion due to Mtv‐3. Certain Vβ such as Vβ15, 18, 20 are found with a low frequency in the spleen, but the fact that they are also scarce in the thymus probably reflects a poor availability of these genetic elements during β chain rearrangement rather than negative selection. Other Vβ, such as Vβ2, Vβ12 and Vβ14 are significantly more abundant in the spleen than in the thymus. This finding was confirmed by mAb staining for Vβ2 and Vβ14. The expansion asymetrically affects the CD4+ subset and can be traced back to the mature, single‐positive thymocyte subset, suggesting an intrathymic positive selection event. Vβ repertoires in infiltrated islets of 13‐ and 18‐week‐old, non‐diabetic mice are polymorphic. Practically all the Vβ found in the peripheral lymphoid tissues are present in the islets, in similar proportions. The major exception is Vβ12, one of the Vβ which is subject to expansion during intrathymic differentiation and which is further augmented in the islets, both at 13 and 18 weeks. This increase probably reflects further peripheral amplification of the Vβ12‐bearing subset due to encounter with the same ligand as in the thymus or with a cross‐reactive motif. Finally, the nucleotide sequencing of all the Vβ segments in usage in the NOD strain confirms the absence of allelic polymorphism of Vβ‐coding regions.
Soluble CD14 from urine copurifies with a potent inducer of cytokines
Authors: Sundan Anders , Gullstein‐Jahr Tove , Otterlei Marit , Ryan Liv , Bazilu Vladimir , Wrightu Samuel D. , Espevik Terje 
Published: March 2007

AbstractHere we report that soluble CD14 isolated from the urine of nephrotic patients (uCD14) contains a potent cytokine inducing activity. CD14 derived from urine appeared to consist of two major polypeptides of about 54 and 48 kDa. In uCD14 isolated from three different nephrotic patients the cytokine‐inducing activity appeared to co‐migrate with the 48‐kDa polypeptide which upon sequencing had the same N‐terminal sequence as native CD14. Treatment of human monocytes and the human astrocytoma cell line U373 with uCD14 resulted in a strong secretion of tumor necrosis factor (TNF) and interleukin‐6, respectively. The cytokine‐inducing activity of the uCD14 preparations was unaffected by the absence of serum. This is in contrast to the activation of human monocytes and U373 cells by lipopolysaccharide (LPS) which is highly dependent on the presence of serum. The cytokine‐inducing activity was not affected by LPS‐binding protein (LBP) or polyclonal rabbit antibodies against LBP The TNF‐inducing activity of uCD14 was also heat labile in contrast to the cytokine‐inducing activity of LPS, which was relatively heat resistant. The results suggest that CD14 may exist in at least two forms of which one is involved in cytokine induction.
Characteristics of fetal thymus‐derived T cell receptor γδ intestinal intraepithelial lymphocytes
Authors: Lin Tesu , Matsuzakiu Goro , Kenaiu Hiroyuki , Kishiharau Kenji , Nabeshimau Shigeki , Fung‐Leungu Wai Ping , Maku Tak W. , Nomotof Kikuo 
Published: March 2007

AbstractWe have previously demonstrated that grafting of CBF1(H‐2b/d) fetal thymus (FTG) under the kidney capsule of congenitally athymic nude mice of BALB/c background (H‐2d) generates a substantial number of T cell receptor (TCR) γδ intestinal intraepithelial lymphocytes (IEL) that were of FTG origin (H‐2b+) (see accompanying report). Here we investigated the characteristics of these FTG‐derived TCR γδ IEL and compared them to the extrathymically derived TCR γδ IEL found in nude mice. Phenotypically, FTG‐derived TCR γδ IEL were similar to their extrathymically derived counterparts in that most were Thy‐1 −, CD5− and CD8αα (homodimer). Vγ and Vδ gene usage in thymus‐derived and extrathymically derived TCR γδ IEL were found to be virtually the same. Functionally, FTG‐derived TCR γδ IEL were similar to the TCR γδ IEL found in euthymic mice as both were relatively anergic to TCR cross‐linking in vitro. However, FTG‐derived TCR γδ IEL differed slightly from extrathymically derived TCR γδ IEL, which were completely nonresponsive to the same in vitro stimulation. Overall, these findings support the view that FTG‐derived and extrathymically derived TCR γδ IEL are almost indistinguishable. Lastly, we demonstrate that despite their thymic origin, development of FTG‐derived TCR γδ IEL partially takes place extrathymically; that is positive selection of FTG‐derived Vδ4 IEL occurs extrathymically. In addition, we demonstrate that the CD8 molecule is not necessary for development and homing of FTG‐derived TCR γδ IEL. This later finding suggests that the CD8αα molecule develops extrathymically for FTG‐derived CD8αα TCR γδ IEL.
In vitro characterization of major ligands for Src homology 2 domains derived from protein tyrosine kinases, from the adaptor protein SHC and from GTPase‐activating protein in Ramos B cells
Authors: Baumann Götz , Maier Daniel , Freuler Felix , Tschopp Claude , Baudisch Kristin , Wienands Jürgen 
Published: March 2007

AbstractAntigen receptors of B lymphocytes transmit their activation signal to the cell interior by associating with and activation of specific non‐receptor tyrosine kinases. Most of these kinases as well as other cytoplasmic effectors contain at least one Src homology 2 (SH2) domain, known to bind tyrosine‐phosphorylated proteins. We examined the binding specificity of SH2 domains from different signaling molecules in B cells and found that each of the SH2 domains tested bound distinct subsets of stimulation‐dependent phosphoproteins in vitro. SH2 domains from Src‐like tyrosine kinases bound predominantly to the HS1 phosphoprotein. The tandem SH2 domains of the ZAP‐70 tyrosine kinase bound to phosphorylated Ig‐β but only weakly to Ig‐α. Also the SHC‐derived SH2 domain formed complexes with the tyrosine‐phosphorylated Ig‐α/β heterodimer, while the C‐ and N‐terminal SH2 domains of GTPase‐activating protein displayed completely different binding preferences. These results suggest that cytoplasmic effector molecules can be recruited to the activated B cell receptor in an SH2‐phosphotyrosine‐mediated manner. The data also provide a possible explanation for the notion that Ig‐α and Ig‐β might couple to different biochemical pathways.
Analysis of individual immunoglobulin λ light chain genes amplified from single cells is inconsistent with variable region gene conversion in germinal‐center B cell somatic mutation
Authors: Fordu John E. , McHeyzer‐Williamsu Michael G. , Lieber Michael R. 
Published: March 2007

AbstractResponding B cells in specific immune responses diversify their immunoglobulin genes and are selected on their variant antigen receptors in the microenviroment of the germinal center. The patterns of mutations previously reported for immunglobulin (Ig) genes have supported mechanistic hypotheses of either error‐prone DNA synthesis or templated variable region gene conversion as the underlying mechanism in the generation of these mutations. To assess the role of gene conversion in germinal‐center somatic mutation, we chose to examine nucleotide changes in mouse λ light chain genes which arose in response to a specific antigen. Laboratory mice possess three Vλ subexons, two of which differ from one another by only seven nucleotides, making these two subexons ideal for gene conversion. In the current study, we used six‐parameter flow cytometry to isolate single λ light chain‐expressing germinal‐center B cells from two different time points in a primary immune response. We then individually amplified and sequenced individual Vλ1 genes from these single cells for mutational analysis. None of the 32 Vλ1 genes, containing a total of 40 mutations, showed evidence of gene conversion from either of the other Vλ subexons. Features such as the replacement to silent ratio of the mutations documented at the earlier time point indicate an absence of antigen‐driven selection. These data indicate that V region gene conversion does not contribute to germinal‐center somatic mutation and that gene conversion is not responsible for targeting mutation specifically to rearranged Ig genes. The biological implications are discussed.
Monoclonal antibodies to murine CD40 define two distinct functional epitopes
Authors: Heath Andrew W. , Wu Wei Wei , Howard Maureen C. 
Published: March 2007

AbstractTwo rat IgG2a antibodies which define distinct epitopes on murine CD40 have been generated. These antibodies specifically bind recombinant murine CD40 expressed on L cells, and the soluble extracellular domain of murine CD40 coated onto microtiter plates. Both antibodies bind B220+ but not B220 murine spleen cells, and immunoprecipitate a 45‐kDa protein from the surface of purified murine splenic B cells. These antibodies exhibit separate functional properties, consistent with the notion that they define two distinct CD40 epitopes. One of the monoclonal antibodies (designated 1C10) directly induces a specific proliferative response from mature murine B cells, up‐regulates several B cell surface antigens, and rescues immature B lymphoma cells from anti‐IgM‐induced growth arrest. The other monoclonal antibody (designated 4F11) exhibits none of these properties, but is capable of synergizing with suboptimal amounts of either anti‐IgM antibodies or the 1C10 agonistic anti‐CD40 antibody to produce an optimal proliferative response of purified small dense B cells. Furthermore, 4F11 antibody synergizes with suboptimal amounts of 1C10 antibody to rescue B lymphoma cells from anti‐IgM‐induced growth arrest. The 1C10 and 4F11 antibodies were unable to cross‐block each other's binding to recombinant CD40 expressed in L cells, providing strong support for the notion that the antibodies recognize distinct epitopes on CD40. The potential implications of two functionally distinct CD40 epitopes are discussed.
T cell specialization at environmental interfaces: T cells from the lung and the female genital tract of lpr and gld mice differ from their splenic and lymph node counterparts
Authors: Ibraghimov Alexander R. , Lynch Richard G. 
Published: March 2007

AbstractMice homozygous for lpr and gld accumulate CD4−CD8− (double‐negative, DN) B220+CD510Thy‐110 αβ T cells in the spleen and lymph nodes (LN), while mucosal gut T cells are normal. To study other mucosa‐associated T cell populations, we examined T cell subsets separated according to expression of αβ T cell receptor, CD4, CD5, CD8, Thy‐1 and B220 in the lung and the female genital tract (FGT) of adult MRL lpr, C3H lpr and C3H gld mice. αβ T cell accumulation was detected in both the FGT and the lungs of lpr and gld mice but, in contrast to the spleen and LN, equal proportions of DN B220+ and CD4+ of CD8+ (single‐positive, SP) B220− T cells were observed in these sites, and the T cells had an increased expression of Thy‐1 and CD5. Staining for CD44, L‐selectin, and CD45RB revealed a higher percentage of effector/memory T cells in lpr and gld lungs and FGT compared to spleens and LN. CD69 expression suggested chronic activation of DN and SP T cells in lpr and gld lungs and FGT. Thus, we show that FGT and lung resident T cells are affected by lpr and gld mutations, but that their phenotypes are distinct from those of systemic T cells. These data suggest that T cells associated with FGT and lung mucosal tissues represent a separate lineage from systemic T cells, and/or that the abnormal T cells in lpr and gld mice are selected against in mucosal surfaces exposed to environmental antigen.
Analysis of the cytolytic activity mediated by natural killer cells from acquired immunodeficiency syndrome patients in response to phytohemagglutinin or anti‐CD16 monoclonal antibody
Authors: Sirianni Maria Caterina , Mezzaromau Ivano , Aiutiu Fernando , Morettaf Alessandro 
Published: March 2007

AbstractThe aim of this study was to assess the cytolytic potential of natural killer (NK) cells from human immunodeficiency virus type 1 (HIV‐1)‐infected patients, at different stages of the disease. Twenty HIV‐1 seronegative donors as well as sixty HIV‐1 seropositive patients were studied. Phytohemagglutinin and/or the anti‐CD16 monoclonal antibody Kd1 were used to redirect the peripheral blood lymphocyte lysis of these patients to the 51Cr‐labeled Fcγ receptor‐positive P815 murine mastocytoma target cell line. In parallel, NK cytotoxicity to tumor targets was investigated. Seronegative as well as HIV‐1 Center for Disease Control (CDC) stage II patients showed maintained cytolytic activity. The cytolytic potential declined with disease progression, starting with CDC IVC2 patients, and was strongly diminished in acquired immunodeficiency syndrome stage patients. This defect was accompanied by decreased cytolytic activity to tumor targets and was not corrected by the in vitro addition of interleukin‐2. The number of cells bearing a mature NK phenotype was normal in all the study groups. Our data suggest that the impaired NK cytotoxicity to tumor targets described during the progression of HIV‐1 disease may be related to the progressive loss of function of surface receptors involved in NK cell triggering.
Exogenous superantigens acutely trigger distinct levels of peripheral T cell tolerance/immunosuppression: Dose‐response relationship
Authors: Miethke Thomas , Wahl Claudia , Gaus Helmut , Heeg Klaus , Wagner Hermann 
Published: March 2007

AbstractLigand‐specific immunosuppression requires an understanding of the parameters that control peripheral T cell tolerance. T cell receptor (TcR) transgenic mice offer a clear advantage for studying post‐thymic tolerance mechanisms in vivo that are operational in a monoclonal T cell population with preselected antigen specificity. Yet it is unclear whether the rules defined in monoclonal T cells of genetically manipulated mice reflect those operative in clonally diverse peripheral T cells of normal mice. To analyze acute tolerance mechanisms in unselected peripheral T cells, we challenged normal mice with the superantigen staphylococcal enterotoxin B (SEB) and analyzed ligand‐reactive Vβ8+ T cells for TcR‐triggered tolerance mechanisms such as anergy, TcR down‐regulation, or apoptosis. Upon challenge with graded doses of SEB (0.001–10 μg) Vβ8− T cells become anergic within 6–16 h. Importantly, a dosage effect of SEB in regard to the level of anergy induced was observed. Anergy induced by low concentrations of SEB (0.001–0.1 μg) is transient and is overcome by clonal growth, while higher concentrations of SEB (0.1–10 μg) cause long‐lasting anergy resistant to cell cycle progression. At high SEB concentrations (1–10 mg) about 50% of the anergic Vβ8+ T cells additionally down‐regulate their TcR‐CD3 complex, followed by a loss of CD2, CD4, CD8 accessory molecules. In parallel, T cell phenotypenegative but genotypically Vβ8+ T cells are generated. The T cell phenotypenegative cells reacquire their Vβ8+ T cell phenotype upon culture in vitro. In vivo, a subset of Vβ8+ cells, defined by an intermediate stage of TcR down‐regulation, i.e. Vβ8lowCD3+ cells, but not T cell phenotype‐negative cells are selectively programmed for apoptosis, which occurs within 1 h. These data suggest that SEB triggers distinct tolerance pathways which operate in a hierarchical fashion in clonally diverse ligand‐reactive T cells. Specifically, the results illustrate the power of exogenous superantigens to exploit these distinct tolerance pathways, thereby achieving distinct levels of immunosuppression.
Double‐negative thymocyte subsets in CD3′ chain‐deficient mice: Absence of HSA+CD44−CD25− cells
Authors: Crompton Tessa , Mooreu Marilyn , MacDonald H. Robson , Malissen Bernard 
Published: March 2007

AbstractDouble‐negative (DN) thymocyte subsets were examined in mice deficient in the CD3′ chain (ζ −/−). The HSA +CD44−CD25− subset was found to be missing, and DN thymocytes seemed to differentiate directly from HSA+CD25+CD44−cells to double‐positive (DP) cells. When fetal thymic ontogeny was examined, we found a marked difference between ζ −/− embryos and heterozygous littermates from embryonic day 17.5, in terms of CD25, CD4 and CD8 expression, and thymus size. The ζ −/− thymocytes failed to down‐regulate CD25 and to expand exponentially. The cell cycle status of adult thymocyte subsets indicated that although the HSA +CD25−CD44− subset was missing, the CD25+ DN population contained normal numbers of cycling cells, and the CD25+ DP cells (which were not detectable in normal mice) contained 5–10% cells in G2/M + S. Taken together these data suggest that the CD3′ chain might have a specific role in the control of proliferation of DN thymocytes during T cell development. Our data clearly show that one can dissociate the signal for a CD25+ DN cell to differentiate (which occurs in the absence of CD3′), from a signal to proliferate and from loss of cell surface CD25.
Neuropeptides are potent modulators of human in vitro immunoglobulin E synthesis
Authors: Aebischer Iwan , Stämpfli Martin R. , Zürcher Adrian , Miescher Sylvia , Urwyler Adrian , Freyu Brigitte , Lugeru Thomas , Whiteu Richard R. , Stadler Beda M. 
Published: March 2007

AbstractWe determined the effect of adrenocorticotropin hormone (ACTH) on the regulation of IgE synthesis. Depending on the concentration, ACTH enhanced or inhibited IgE synthesis in a culture system where IgE synthesis was induced with interleukin‐4 (IL‐4) and anti‐CD40 monoclonal antibody in peripheral blood mononuclear cells. Similar effects on IgE synthesis were observed by adding ACTH‐related peptides, e.g. corticotropin‐releasing factor (CRF), the inducer of ACTH, or α‐melanocyte stimulating hormone (α‐MSH), a cleavage product of ACTH. However, ACTH had no effect on IgG or IgM synthesis in this culture system. ACTH did not act directly on either B or T cells as there was no influence on IgE synthesis in a system using purified B cells alone or co‐cultured with T cells. The effect of ACTH on IgE synthesis was mediated by accessory cells. This was shown by priming purified CD14‐positive monocytes with ACTH and reconstitution experiments. Therefore, these findings suggest that ACTH and the related peptides CRF and α‐MSH can influence the microenvironment modulating an IL‐4 and anti‐CD40 monoclonal antibody driven class switching to IgE via accessory cells.