bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pre-B Cell Receptor-Mediated Selection of Pre-B Cells Synthesizing Functional μ Heavy Chains
Authors: Kline Gregory H. , Hartwell Laura , Beck-Engeser Gabrielle B. , Keyna Ulrike , Zaharevitz Samantha , Klinman Norman R. , Jäck Hans-Martin 
Published: December 2022

AbstractIg gene rearrangements could generate VH-D-JH joining sequences that interfere with the correct folding of a μ-chain, and thus, its capability to pair with IgL chains. Surrogate light (SL) chain might be the ideal molecule to test the capacity of a μ-chain to pair with a L chain early in development, in that only pre-B cells that assemble a membrane μ-SL complex would be permitted to expand and further differentiate. We have previously identified two SL chain nonpairing VH81X-μ-chains with distinct VH-D-JH joining regions. Here, we show that one of these VH81X-μ-chains does not rescue B cell development in JH knock-out mice, because flow cytometric analysis of bone marrow cells from VH81X-μ transgenic JH knock-out mice revealed normal numbers of pro-B cells, but essentially no pre-B and surface IgM+ B cells. Immunoprecipitation analysis of transfected pre-B and hybridoma lines revealed that the same μ-chain fails to pair not only with SL chain but also with four distinct κ L chains. These findings demonstrate that early pre-B cells are selected for maturation on the basis of the structure of a μ-chain, in particular its VH-D-JH joining or CDR3 sequence, and that one mechanism for this selection is the capacity of a μ-chain to assemble with SL chain. Therefore, we propose a new function of SL chain in early B cell development: SL chain is part of a quality control mechanism that tests a μ-chain for its ability to pair with conventional L chains.
Endogenous Basic Fibroblast Growth Factor Is Essential for Cyclin E-CDK2 Activity in Multiple External Cytokine-Induced Proliferation of AIDS-Associated Kaposi’s Sarcoma Cells: Dual Control of AIDS-Associated Kaposi’s Sarcoma Cell Growth and Cyclin E-CDK2 Activity by Endogenous and External Signals
Authors: Murakami-Mori Kaoru , Mori Shunsuke , Nakamura Shuji 
Published: December 2022

AbstractAIDS-associated Kaposi’s sarcoma (KS) cell, a key element for development of KS lesions, proliferates in response to external cytokines, such as oncostatin M, the soluble IL-6R-IL-6 complex, TNF-α, and IL-1β. In addition, the KS cell-produced basic fibroblast growth factor (bFGF) was reported to function as an autocrine growth factor. However, little is known of the exact roles of these external growth factors and endogenous bFGF on proliferation of KS cells, and underlying intracellular events have remained to be defined. We obtained evidence that anti-bFGF Ab abolished growth of KS cells by preventing S phase entry of the cell cycle, even in the presence of the external growth factors. Blockade of the FGF action profoundly inhibited cyclin E expression and cyclin-dependent kinase-2 (CDK2) activity, but not D-type cyclin expression and CDK4 activity. Exogenously added acidic FGF (aFGF), which generated a rapid tyrosine phosphorylation of FGFR1 and FGFR2 on KS cells, reversed the inhibitory effects of anti-bFGF Ab. Thus, FGF actions are essential for cyclin E-CDK2 activity and S phase entry. We also observed that the presence of external growth factors markedly induced cyclin E-CDK2 activity and S phase entrance, while the addition of aFGF or bFGF alone was insufficient to induce these responses. All this evidence shows that integration of the activities of external growth factors and endogenous bFGF is required for full activation of cyclin E-CDK2 activity and KS cell proliferation.
Receptor-Specific Allelic Exclusion of TCRVα-Chains During Development
Authors: Boyd Richard , Kozieradzki Ivona , Chidgey Ann , Mittrücker Hans-Willi , Bouchard Dennis , Timms Emma , Kishihara Kenji , Ong Christopher J. , Chui Daniel , Marth Jamey D. , Mak Tak W. , Penninger Josef M. 
Published: December 2022

AbstractExpression of a single Ag receptor on lymphocytes is maintained via allelic exclusion that generates cells with a clonal receptor repertoire. We show in normal mice and mice expressing functionally rearranged TCRαβ transgenes that allelic exclusion at the TCRα locus is not operational in immature thymocytes, whereas most mature T cells express a single TCRVα-chain. TCRVα allelic exclusion in mature thymocytes is regulated through a CD45 tyrosine phosphatase-mediated signal during positive selection. Using functional and genetic systems for selection of immature double TCRVα+ thymocytes, we show that peptide-specific ligand recognition provides the signal for allelic exclusion, i.e., mature T cells maintain expression of the ligand-specific TCRVα-chain, but lose the nonfunctional receptor. Whereas activation of TCRVβ-chains or CD3ε leads to receptor internalization, TCRVα ligation promotes retention of the TCR on the cell surface. Although both TCRVα- and TCRVβ-chains trigger phosphotyrosine signaling, only the TCRVβ-chain mediates membrane recruitment of the GTPase dynamin. These data indicate that TCRVα-directed signals for positive selection control allelic exclusion in T cells, and that developmental signals can select for single receptor usage.
IL-2 Receptor α-Chain Expression Is Independently Regulated in Primary and Secondary Lymphoid Organs
Authors: Demaison Christophe , Fiette Laurence , Blanchetière Valérie , Schimpl Anneliese , Thèze Jacques , Froussard P. 
Published: December 2022

Abstract
The IL-2R is composed of three chains: IL-2Rα, IL-2Rβ, and IL-2Rγ. In mice, IL-2Rα is critical and determines IL-2 binding to the tripartite IL-2R complex. To extend our previous studies, which demonstrated that IL-2 regulates IL-2Rα expression in vitro, we have analyzed expression in IL-2-deficient mice in vivo. As in control animals, CD4−CD8− thymocytes and bone marrow-derived B220+ pre-B cells were Il-2Rα positive. In contrast, activated lymph node and splenic CD4 T cells (CD4+CD69+) were found to be IL-2Rα negative, whereas ∼20% of the same cell populations from the MLR/lpr strain, which also accumulate large numbers of CD4-activated T cells in the presence of intact IL-2, retained expression. A similar pattern of IL-2Rα expression was found among splenic CD8 cells from IL-2−/− and IL-2+/− animals. These findings demonstrate that in primary lymphoid organs, IL-2 is not directly involved in IL-2Rα expression. However, at the level of mature lymphocytes, and more specifically CD4 T cells, IL-2 remains in vivo, as in vitro, the most critical cytokine controlling both IL-2Rα expression and sensitivity to IL-2.
Initial Cytokine Exposure Determines Function of Macrophages and Renders Them Unresponsive to Other Cytokines
Authors: Erwig Lars-Peter , Kluth David C. , Walsh Garry M. , Rees Andrew J. 
Published: December 2022

AbstractThe functional properties of infiltrating macrophages (Mφ) must be tightly regulated to facilitate appropriate responses to complex conditions in an inflammatory focus. This study was designed to ascertain whether uncommitted Mφ that have been exposed to combinations of cytokines with opposing functions develop properties dictated by one cytokine or by cytokine mixtures. Uncommitted rat bone marrow-derived Mφ (BMDMs) were incubated with IFN-γ, TNF-α, TGF-β, IL-4, IL-6, and IL-10 alone or sequentially in combinations. After 48 h, function was assessed by nitric oxide (NO) generation, uptake of apoptotic neutrophils, and β-glucuronidase expression. IFN-γ followed 4 h later by TNF-induced NO generation. The pretreatment of BMDMs before IFN-γ priming with TNF, TGF-β, and IL-4 suppressed NO generation by 87%, 92%, and 85%, respectively; IL-10 had no effect. The same cytokines administered at 4 h after IFN priming had no effect on NO generation. The uptake of apoptotic polymorphonuclear leukocytes was augmented by TNF (40% vs 29% controls; p &lt; 0.05) and decreased by IFN-γ, IL-10, and IL-4. The TNF response was unaffected by subsequent treatment with IFN-γ, IL-4, or IL-10. Similarly, the decreased polymorphonuclear leukocyte uptake induced by IFN-γ, IL-4, or IL-10 was unaffected by the subsequent addition of TNF. β-glucuronidase expression was increased by TGF-β and decreased by IFN-γ. These responses were not modified by cytokines with the opposing function. Thus, the functional response of BMDMs to complex mixtures of cytokines was determined by the first cytokine to which they were exposed. Once activated, BMDMs become unresponsive to alternative activating signals, a finding which has obvious implications for Mφ function in vivo.
Cutting Edge: FcγRII-B1 Regulates the Presentation of B Cell Receptor-Bound Antigens
Authors: Minskoff Stacey A. , Matter Karl , Mellman Ira 
Published: December 2022

AbstractFcγ receptors (FcγRII) on B lymphocytes negatively regulate B cell receptor (BCR)-dependent activation upon cross-linking of the two receptors. The mechanism reflects the ability of the FcγRII cytoplasmic tail to recruit specific phosphatases that inactivate elements of the BCR-signaling cascade. We now show that cross-linking also blocks the processing and presentation of BCR-bound Ag. This occurs because the FcγRII isoform typically expressed by B cells (FcγRII-B1) is incompetent for endocytosis. When cross-linked, FcγRII-B1 acts as a dominant negative inhibitor of BCR endocytosis. In contrast, cross-linking of endocytosis-competent FcγRII isoforms did not inhibit endocytosis or processing of BCR-bound Ag. Thus, FcγRII-B1 acts not only to prevent B cell activation under conditions of Ab excess, but also to prevent clonotypic T cell activation by inhibiting the ability of B cells to generate specific MHC class II-bound TCR ligands.
Quiescence-Inducing and Antiapoptotic Activities of IL-15 Enhance Secondary CD4+ T Cell Responsiveness to Antigen
Authors: Dooms Hans , Desmedt Marjory , Vancaeneghem Sabine , Rottiers Pieter , Goossens Vera , Fiers Walter , Grooten Johan 
Published: December 2022

AbstractIL-15 shows functional redundancy with IL-2 due to its usage of the β and γc subunit of the IL-2R. Yet, the requirement of IL-15 for an IL-15Rα chain for high affinity interaction and the separate cellular sources of IL-2 and IL-15 suggest divergent activities for both cytokines. We compared the growth-inducing and proapoptotic or antiapoptotic activities of IL-15 and IL-2 on mature CD4+ T lymphocytes in the presence or absence of TCR occupancy. We found that the nature of IL-15 activity was critically dependent on the activation status of the T cells. In the absence of TCR triggering, IL-15 did not exert the growth factor activity of IL-2, but induced a quiescent phenotype, characterized by maintenance of the cells in the G0/G1 phase of the cell cycle and down-regulation of CD25, CD71, and CD95 expression. In the presence of appropriate TCR engagement, the IL-15-induced quiescent T cells were resistant against TCR-induced cell death and proliferated strongly. IL-2-treated cells, on the contrary, were sensitized to cell death, resulting in a negative feedback on cellular expansion and weak proliferative responsiveness. Consecutive action of IL-15 during the distinct phases of an in vitro immune response markedly increased the cell output of a second antigenic stimulation, as compared with IL-2. These results imply that during immune reactivity in vivo, IL-15 may take over from the transiently available IL-2 the role of survival factor but not of growth factor, hence promoting the long term maintenance of resting, Ag-experienced CD4+ T cells.
TNF-Related Apoptosis-Inducing Ligand (TRAIL) Induces Apoptosis in Fas Ligand-Resistant Melanoma Cells and Mediates CD4 T Cell Killing of Target Cells
Authors: Thomas Wayne D. , Hersey Peter 
Published: December 2022

AbstractWe have previously shown that melanoma cells were resistant to apoptosis induced by TNF family members Fas ligand (FasL), TNF-α, and CD40L. FasL also was not involved in CD4 T cell-mediated killing of melanoma cells. In the present study, we have tested melanoma cells for their susceptibility to apoptosis induced by human TNF-related apoptosis-inducing ligand (TRAIL) and the ability of a mAb against TRAIL to inhibit apoptosis and CD4 CTL-mediated killing of melanoma and Jurkat target cells. The results show that TRAIL-induced apoptosis in cells from 7 of 10 melanoma cell lines tested as well as in Jurkat T cells. Susceptibility to apoptosis was increased in some of the cell lines by treatment with cyclohexamide or actinomycin D. The melanoma cells were resistant to apoptosis induced by FasL, TNF-α, and CD40L. mAb M180 against TRAIL inhibited apoptosis induced by TRAIL. It was also found to inhibit CD4 CTL-mediated killing of Jurkat T cells as well as autologous and allogeneic melanoma cells. The degree of inhibition produced by the mAb varied between different clones of CTL and according to the susceptibility of the target cells to TRAIL-induced apoptosis. These results suggest that TRAIL is an important mediator of cell death induced by CTL and may have an important therapeutic role against human melanoma.
Protein Kinase C Regulates Fas (CD95/APO-1) Expression
Authors: Wang Ruoxiang , Zhang Liying , Yin Deling , Mufson R. Allan , Shi Yufang 
Published: December 2022

AbstractFas (CD95/APO-1) is a transmembrane protein of the TNF/neuron growth factor receptor family. Ligation of Fas by specific Abs or Fas ligand (FasL/CD95 ligand) induces rapid apoptotic cell death in a variety of cell types. Despite progress in understanding the death signals transduced from Fas, very little is known with regard to the mechanisms by which Fas expression is regulated. Using our previously established murine T cell hybridoma model A1.1, we show that specific protein kinase C (PKC) inhibitors could block activation-induced Fas expression and apoptosis. The activation of PKC with PMA or 1-oleoyl-2-acetyl-sn-glycerol could mimic the TCR signal by inducing the expression of Fas but not FasL. PKC-dependent Fas expression was also observed in several murine and human tumor cell lines. Since the inhibition of Ca2+ redistribution by an inhibitor of intracellular Ca2+ mobilization, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride, inhibited TCR-induced FasL but not Fas, the expression of Fas appears to be independent of Ca2+ mobilization. Significantly, expression of the newly identified Fas-regulatory gene, TDAG51, was found to be dependent upon the activity of PKC. PKC activation only induced Fas expression in cells expressing wild-type TDAG51. Thus, Fas expression is likely mediated by PKC through TDAG51.
Maturation of B Cell Precursors Is Impaired in Thymic-Deprived Nude and Old Mice
Authors: Szabo Paul , Zhao Kesheng , Kirman Irena , Le Maoult Joel , Dyall Rubendra , Cruikshank William , Weksler Marc E. 
Published: December 2022

Abstract
We have previously reported that bone marrow B cell precursors from thymic-deprived nude and old mice express less recombination-activating gene-1 (RAG-1) mRNA than they do in young euthymic mice. We now report that both nude and old mice have decreased bone marrow pre-B cells and that fewer pre-B cells express RAG protein. This combination of events appears to be the basis for the lower level of bone marrow RAG mRNA in thymic-deprived mice. A link between thymic function and B cell development was suggested by the similar kinetics of thymic involution and of declining bone marrow RAG-1 gene expression during aging. Support for this hypothesis was obtained by demonstrating that injection of supernatant medium from activated CD8+ but not CD4+ young T cells from mice increases RAG mRNA, RAG protein, and the number of bone marrow pre-B cells in nude and old mice. Furthermore, in vivo CD8+ T cells also regulate bone marrow RAG gene expression. Thus, mice deficient in CD8+ T cells expressed levels of RAG-1 mRNA in their bone marrow that were only 10% of those observed in normal or CD4+ T cell-deficient mice. IL-16 was detected in the supernatant medium from activated T cell cultures, and injection of nanogram quantities of recombinant IL-16 (rIL-16) into nude or old mice increased the levels of RAG mRNA in bone marrow B cell precursors and the number of bone marrow pre-B cells. We conclude that the impaired development of B cells within the bone marrow of thymic-deprived nude and old mice can be reversed, at least in part, by the administration of rIL-16.
Distinct Stage-Specific cis-Active Transcriptional Mechanisms Control Expression of T Cell Coreceptor CD8α at Double- and Single-Positive Stages of Thymic Development
Authors: Zhang Xiao-Li , Seong Rho , Piracha Rafia , Larijani Mani , Heeney Matthew , Parnes Jane R. , Chamberlain John W. 
Published: December 2022

Abstract
Developing thymocytes that give rise to CD8+ (cytotoxic) and CD4+ (helper) αβ-TCR T lymphocytes go through progressive stages of expression of coreceptors CD8 and CD4 from being negative for both (the double-negative stage), to coexpressing both (the double-positive (DP) stage), to a mutually exclusive sublineage-specific expression of one or the other (the single-positive (SP) stage). To delineate the mechanisms underlying regulation of CD8 during these developmental transitions, we have examined expression of a series of mouse CD8α gene constructs in developing T cells of conventional and CD8α “knock-out” transgenic mice. Our results indicate that cis-active transcriptional control sequences essential for stage- and sublineage-specific expression lie within a 5′ 40-kb segment of the CD8 locus, ∼12 kb upstream of the CD8α gene. Studies to characterize and sublocalize these cis sequences showed that a 17-kb 5′ subfragment is able to direct expression of the CD8α gene up to the CD3intermediate DP stage but not in more mature DP or SP cells. These results indicate that stage-specific expression of CD8α in developing T cells is mediated by the differential activity of multiple functionally distinct cis-active transcriptional control mechanisms. It will be important to determine the relationship of “switching” between these cis mechanisms and selection.
Bacterial Surface Proteins Recognized by CD4+ T Cells During Murine Infection with Listeria monocytogenes
Authors: Campbell Daniel J. , Shastri Nilabh 
Published: December 2022

Abstract
Optimal immunity to the Gram-positive pathogen Listeria monocytogenes (LM) requires both CD8+ and CD4+ antigen-specific T cell responses. Understanding how CD4+ T cells function in an immune response to LM and how bacterial proteins are processed to peptide/MHC class II complexes in infected cells requires identification of these proteins. Using LacZ-inducible, LM-specific CD4+ T cells as probes, we identified two immunogenic LM proteins by a novel expression cloning strategy. The antigenic peptides contained within these proteins were defined by deletion analysis of the genes, and their antigenicity was confirmed with synthetic peptides. The nucleotide sequences of the genes showed that they encode previously unknown LM proteins that are homologous to surface proteins in other bacterial species. Consistent with their surface topology, mild trypsin treatment of LM protoplasts ablated T cell recognition of these Ags. These findings establish a general strategy for identifying unknown CD4+ T cell Ags and demonstrate that LM surface proteins can provide the peptides for presentation by MHC class II molecules that are specific targets for CD4+ T cells during murine LM infection.
Molecular Cloning and Immunologic Reactivity of a Novel Low Molecular Mass Antigen ofMycobacterium tuberculosis
Authors: Coler Rhea N. , Skeiky Yasir A. W. , Vedvick Thomas , Bement Teresa , Ovendale Pamela , Campos-Neto Antonio , Alderson Mark R. , Reed Steven G. 
Published: December 2022

AbstractPolypeptide Ags present in the culture filtrate of Mycobacterium tuberculosis were purified and evaluated for their ability to stimulate PBMC from purified protein derivative (PPD)-positive healthy donors. One such Ag, which elicited strong proliferation and IFN-γ production, was further characterized. The N-terminal amino acid sequence of this polypeptide was determined and used to design oligonucleotides for screening a recombinant M. tuberculosis genomic DNA library. The gene (Mtb 8.4) corresponding to the identified polypeptide was cloned, sequenced, and expressed in Escherichia coli. The predicted m.w. of the recombinant protein without its signal peptide was 8.4 kDa. By Southern analysis, the DNA encoding this mycobacterial protein was found in the M. tuberculosis substrains H37Rv, H37Ra, Erdman, and “C” strain, as well as in certain other mycobacterial species, including Mycobacterium avium and Mycobacterium bovis BCG (bacillus Calmette-Guérin, Pasteur). The Mtb 8.4 gene appears to be absent from the environmental mycobacterial species examined thus far, including Mycobacterium smegmatis, Mycobacterium gordonae, Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium scrofulaceum. Recombinant Mtb 8.4 Ag induced significant proliferation as well as production of IFN-γ, IL-10, and TNF-α, but not IL-5, from human PBMC isolated from PPD-positive healthy donors. Mtb 8.4 did not stimulate PBMC from PPD-negative donors. Furthermore, immunogenicity studies in mice indicate that Mtb 8.4 elicits a Th1 cytokine profile, which is considered important for protective immunity to tuberculosis. Collectively, these results demonstrate that Mtb 8.4 is an immunodominant T cell Ag of M. tuberculosis.
The Role of the Bacterial Membrane Protein ActA in Immunity and Protection Against Listeria monocytogenes
Authors: Darji Ayub , Bruder Dunja , zur Lage Susanne , Gerstel Birgit , Chakraborty Trinad , Wehland Jürgen , Weiss Siegfried 
Published: December 2022

Abstract
ActA, an essential virulence factor of Listeria monocytogenes, is an integral membrane protein that is required for intracellular motility, cell-to-cell spread, and rapid dissemination of the bacteria in the infected host. To reveal cytotoxic T cell responses against ActA we introduced a recombinant soluble form of ActA into the MHC class I-processing compartment of APC using a variant of listeriolysin mutated within its immunodominant MHC class I epitope. With this experimental system we demonstrate that T cells are induced against ActA during a sublethal infection with L. monocytogenes. However, adoptively transferred cytotoxic CD8+ T cells specific for ActA did not protect mice against a subsequent challenge with this pathogen. This was due to an inability of APC to present ActA by either MHC class I or class II molecules as long as ActA remained tethered to the surface of intracellular viable bacteria. ActA was only presented when L. monocytogenes were engineered to secrete ActA or when the bacteria were killed by antibiotics during the assay. These findings raise questions on the general use of membrane proteins of pathogens as candidates for subunit vaccines.