bluuebunny/crossref_metadata_2025 huggingface dataset:
A Recombinant Homotrimer, Composed of the α Helical Neck Region of Human Surfactant Protein D and C1q B Chain Globular Domain, Is an Inhibitor of the Classical Complement Pathway
Authors: Kishore Uday , Strong Peter , Perdikoulis Michael V. , Reid Kenneth B. M.
Published: April 2014

The first step in the activation of the classical complement pathway by immune complexes involves the binding of the six globular heads of C1q to the Fc regions of IgG or IgM. The globular heads of C1q (gC1q domain) are located C-terminal to the six triple-helical stalks present in the molecule, each head being composed of the C-terminal halves of one A, one B, and one C chain. The gC1q modules are also found in a variety of noncomplement proteins, such as type VIII and X collagens, precerebellin, hibernation protein, multimerin, Acrp-30, and saccular collagen. In several of these proteins, the chains containing these gC1q modules appear to form a homotrimeric structure. Here, we report expression of an in-frame fusion of a trimerizing neck region of surfactant protein D with the globular head region of C1q B chain as a fusion to Escherichia coli maltose binding protein. Following cleavage by factor Xa and removal of the maltose binding protein, the neck and globular region, designated ghB3, formed a soluble, homotrimeric structure and could inhibit C1q-dependent hemolysis of IgG- and IgM-sensitized sheep erythrocytes. The functional properties of ghB3 indicate that the globular regions of C1q may adopt a modular organization in which each globular head of C1q may be composed of three structurally and functionally independent domains, thus retaining multivalency in the form of a heterotrimer. The finding that ghB3 is an inhibitor of C1q-mediated complement activation opens up the possibility of blocking activation at the first step of the classical complement pathway.
Inherited IL-12 Unresponsiveness Contributes to the High LPS Resistance of theLpsd C57BL/10ScCr Mouse
Authors: Merlin Thomas , Sing Andreas , Nielsen Peter J. , Galanos Chris , Freudenberg Marina A.
Published: April 2014

Lps d mouse strains are characterized by the presence of a defective Lps/tlr4 gene that make them refractory to the biological activity of LPS. One of the mouse strains commonly used to study LPS defects is the C57BL/10ScCr (Cr) strain. However, unlike other Lpsd strains, the Cr strain also has a heavily impaired IFN-γ response to micro-organisms. As a consequence, unlike other Lpsd mouse strains, they do not acquire a partial LPS susceptibility when treated with sensitizing bacteria. Because IL-12 is important for the microbial induction of IFN-γ, we investigated whether the production or function of IL-12 might be defective in Cr mice. IL-12 mRNA (p35 and p40) was present in the spleen of untreated Cr mice, IL-12p40 mRNA was inducible in mice injected with live or killed Salmonella typhimurium, and IL-12 (p70) was inducible in macrophages by bacteria. Thus, Cr mice exhibit normal IL-12 responses. In functional tests, splenocytes of untreated or of S. typhimurium-infected mice failed to produce IFN-γ when stimulated with murine rIL-12 or with a combination of IL-12 and murine rIL-18 or Con A. Furthermore, Cr mice were identical with IL-12p35/p40 and IL-12 receptor β1 knockout mice in their impaired in vivo and in vitro IFN-γ responses to bacteria. Thus, Cr mice carry a second genetic defect unrelated to the Lps/tlr4 mutation that underlies the IL-12 unresponsiveness and contributes to the LPS resistance and impaired innate immune response in this strain.
CD11b/CD18 Acts in Concert with CD14 and Toll-Like Receptor (TLR) 4 to Elicit Full Lipopolysaccharide and Taxol-Inducible Gene Expression
Authors: Perera Pin-Yu , Mayadas Tanya N. , Takeuchi Osamu , Akira Shizuo , Zaks-Zilberman Meirav , Goyert Sanna M. , Vogel Stefanie N.
Published: April 2014

Overproduction of inflammatory mediators by macrophages in response to Gram-negative LPS has been implicated in septic shock. Recent reports indicate that three membrane-associated proteins, CD14, CD11b/CD18, and Toll-like receptor (TLR) 4, may serve as LPS recognition and/or signaling receptors in murine macrophages. Therefore, the relative contribution of these proteins in the induction of cyclooxygenase 2 (COX-2), IL-12 p35, IL-12 p40, TNF-α, IFN-inducible protein (IP)-10, and IFN consensus sequence binding protein (ICSBP) genes in response to LPS or the LPS-mimetic, Taxol, was examined using macrophages derived from mice deficient for these membrane-associated proteins. The panel of genes selected reflects diverse macrophage effector functions that contribute to the pathogenesis of septic shock. Induction of the entire panel of genes in response to low concentrations of LPS or Taxol requires the participation of both CD14 and TLR4, whereas high concentrations of LPS or Taxol elicit the expression of a subset of LPS-inducible genes in the absence of CD14. In contrast, for optimal induction of COX-2, IL-12 p35, and IL-12 p40 genes by low concentrations of LPS or by all concentrations of Taxol, CD11b/CD18 was also required. Mitigated induction of COX-2, IL-12 p35, and IL-12 p40 gene expression by CD11b/CD18-deficient macrophages correlated with a marked inhibition of NF-κB nuclear translocation and mitogen-activated protein kinase (MAPK) activation in response to Taxol and of NF-κB nuclear translocation in response to LPS. These findings suggest that for expression of a full repertoire of LPS-/Taxol-inducible genes, CD14, TLR4, and CD11b/CD18 must be coordinately engaged to deliver optimal signaling to the macrophage.
IL-8 Induces a Transient Arrest of Rolling Eosinophils on Human Endothelial Cells
Authors: Ulfman Laurien H. , Joosten Dianne P. H. , van der Linden Jan A. M. , Lammers Jan-Willem J. , Zwaginga Jaap Jan , Koenderman Leo
Published: April 2014

Eosinophils exhibit a rolling interaction with E-selectin-expressing endothelium, and need to be activated by inflammatory mediators to firmly adhere to this surface. This study shows that IL-8 induces a transient arrest of unprimed eosinophils that roll on E-selectin present on TNF-α-activated HUVEC in an in vitro flow chamber. This process was antagonized by neutralizing Abs directed against IL-8 showing the specificity of the IL-8 effect. Furthermore, blocking Abs against both α4 and β2 integrins inhibited the IL-8-induced transient arrest while these Abs had no effect when they were added separately. The IL-8-induced arrest was pertussis toxin sensitive. Studying the effect of IL-8 in more detail, we evaluated putative changes in intracellular Ca2+ concentration in eosinophils induced by IL-8. We could show that IL-8 induces a transient rise in intracellular Ca2+ concentration in ∼40% of the cells provided that the eosinophils are interacting with endothelial cells or fibronectin-coated surfaces. Together these data show that resting eosinophils respond to IL-8 provided that the cells adhere on physiological surfaces. The induction of a transient arrest provides a new level of chemokine-induced regulation of leukocyte adhesion under flow conditions.
Central Nervous System Expression of IL-10 Inhibits Autoimmune Encephalomyelitis
Authors: Cua Daniel J. , Hutchins Beth , LaFace Drake M. , Stohlman Stephen A. , Coffman Robert L.
Published: April 2014

Multiple sclerosis, an inflammatory, demyelinating disease of the CNS currently lacks an effective therapy. We show here that CNS inflammation and clinical disease in experimental autoimmune encephalomyelitis, an experimental model of multiple sclerosis, could be prevented completely by a replication-defective adenovirus vector expressing the anti-inflammatory cytokine IL-10 (replication-deficient adenovirus expressing human IL-10), but only upon inoculation into the CNS where local infection and high IL-10 levels were achieved. High circulating levels of IL-10 produced by i.v. infection with replication-deficient adenovirus expressing human IL-10 was ineffective, although the immunological pathways for disease are initiated in the periphery in this disease model. In addition to this protective activity, intracranial injection of replication-deficient adenovirus expressing human IL-10 to mice with active disease blocked progression and accelerated disease remission. In a relapsing-remitting disease model, IL-10 gene transfer during remission prevented subsequent relapses. These data help explain the varying outcomes previously reported for systemic delivery of IL-10 in experimental autoimmune encephalomyelitis and show that, for optimum therapeutic activity, IL-10 must either access the CNS from the peripheral circulation or be delivered directly to it by strategies including the gene transfer described here.
Necessity of Thromboxane A2 for Initiation of Platelet-Mediated Contact Sensitivity: Dual Activation of Platelets and Vascular Endothelial Cells
Authors: Mitsuhashi Motoki , Tanaka Akane , Fujisawa Chie , Kawamoto Keiko , Itakura Atsuko , Takaku Mikio , Hironaka Takasi , Sawada Shuzo , Matsuda Hiroshi
Published: April 2014

To investigate the crucial role of platelet-derived thromboxane A2 (TXA2) in initiating Ag-specific contact sensitivity (CS), a platelet-dependent CS model using genetically mast cell-deficient W/Wv mice, was provided. In vivo treatment with BAYu3405, a TXA2 receptor antagonist, markedly suppressed CS responses in a dose-dependent manner. This inhibitory effect occurred when BAYu3405 was administered before an early initiating phase, suggesting that TXA2 may be a potent initiator of platelet-mediated CS responses. When platelets were pretreated with BAYu3405 in vitro, platelet aggregation as well as serotonin release, which is able to induce the early phase response allowing local recruitment of CS effector T cells due to direct activation of vascular endothelial cells, was inhibited. The addition of U46619, a TXA2 agonist, or a mixture of platelets and thrombin-enhanced expression of both ICAM-1 and VCAM-1 on isolated mouse aortic endothelial cells, which was completely abolished by pretreatment with BAYu3405. Furthermore, intradermal injection of U46619 into the ear of platelet-depleted mice led to CS responses with marked expression of ICAM-1 and VCAM-1 on the vascular endothelium. These findings suggest that TXA2 generated from platelets activated with Ag may mediate initiation of CS responses through inducing serotonin release from platelets and the subsequent aggregation and up-regulated expression of ICAM-1 and VCAM-1 on vascular endothelial cells.
A Novel Anionic Modification of N-Glycans on Mammalian Endothelial Cells Is Recognized by Activated Neutrophils and Modulates Acute Inflammatory Responses
Authors: Srikrishna Geetha , Toomre Derek K. , Manzi Adriana , Panneerselvam Krishnasamy , Freeze Hudson H. , Varki Ajit , Varki Nissi M.
Published: April 2014

We previously reported an unusual carboxylated modification on N-glycans isolated from whole bovine lung. We have now raised IgG mAbs against the modification by immunization with biotinylated aminopyridine-derivatized glycans enriched for the anionic species and screening for Abs whose reactivities were abrogated by carboxylate neutralization of bovine lung glycopeptides. One such Ab (mAb GB3.1) was inhibited by carboxylated bovine lung glycopeptides and other multicarboxylated molecules, but not by glycopeptides in which the carboxylate groups were modified. The Ab recognized an epitope constitutively expressed on bovine, human, and other mammalian endothelial cells. Stimulated, but not resting, neutrophils bound to immobilized bovine lung glycopeptides in a carboxylate-dependent manner. The binding of activated neutrophils to immobilized bovine lung glycopeptides was inhibited both by mAb GB3.1 and by soluble glycopeptides in a carboxylate-dependent manner. The Ab also inhibited extravasation of neutrophils and monocytes in a murine model of peritoneal inflammation. This inhibition of cell trafficking correlated with the increased sequestration but reduced transmigration of leukocytes that were found to be adherent to the endothelium of the mesenteric microvasculature. Taken together, these results indicate that these novel carboxylated N-glycans are constitutively expressed on vascular endothelium and participate in acute inflammatory responses by interaction with activated neutrophils.
Persistence of Infectious HIV on Follicular Dendritic Cells
Authors: Smith Beverly A. , Gartner Suzanne , Liu Yiling , Perelson Alan S. , Stilianakis Nikolaos I. , Keele Brandon F. , Kerkering Thomas M. , Ferreira-Gonzalez Andrea , Szakal Andras K. , Tew John G. , Burton Gregory F.
Published: April 2014

Follicular dendritic cells (FDCs) trap Ags and retain them in their native state for many months. Shortly after infection, HIV particles are trapped on FDCs and can be observed until the follicular network is destroyed. We sought to determine whether FDCs could maintain trapped virus in an infectious state for long periods of time. Because virus replication would replenish the HIV reservoir and thus falsely prolong recovery of infectious virus, we used a nonpermissive murine model to examine maintenance of HIV infectivity in vivo. We also examined human FDCs in vitro to determine whether they could maintain HIV infectivity. FDC-trapped virus remained infectious in vivo at all time points examined over a 9-mo period. Remarkably, as few as 100 FDCs were sufficient to transmit infection throughout the 9-mo period. Human FDCs maintained HIV infectivity for at least 25 days in vitro, whereas virus without FDCs lost infectivity after only a few days. These data indicate that HIV retained on FDCs can be long lived even in the absence of viral replication and suggest that FDCs stabilize and protect HIV, thus providing a long-term reservoir of infectious virus. These trapped stores of HIV may be replenished with replicating virus that persists even under highly active antiretroviral therapy and would likely be capable of causing infection on cessation of drug therapy.
Normal B Cells Express51p1-Encoded Ig Heavy Chains That Are Distinct From Those Expressed by Chronic Lymphocytic Leukemia B Cells
Authors: Widhopf George F. , Kipps Thomas J.
Published: April 2014

51p1 is an allele of VH1-69 that frequently is expressed by chronic lymphocytic leukemia (CLL) B cells with little or no somatic mutation. The rearranged 51p1 genes expressed by CLL B cells have a distinctive use of D segments D3-3/DXP4 and D3-10/DXP′1, a favored use of JH6, and a longer third complementarity-determining region than the rearranged Ig genes used by CLL B cells that express VH1 genes other than VH1-69. We examined the 51p1-encoded Ig expressed by blood B cells of healthy donors. In contrast to the infrequent use of JH4 by 51p1-expressing CLL (e.g., 4%), 36% of the rearranged 51p1 sequences from normal blood B cells used JH4. Furthermore, the D segment use of the rearranged 51p1 sequences from normal blood B cells was not restricted, but reflected the D segment use of nonselected IgH of normal B cells. Finally, the mean length of the third complementarity-determining region for the 51p1 genes of normal blood B cells was 14.6 ± 4.3 (SD) codons. This is significantly shorter than that noted for 51p1-expressing CLL B cells (18.8 ± 3.2; p < 0.0001, n = 51). This study demonstrates that the 51p1-encoded IgH expressed in CLL are not representative of the 51p1-encoded IgH expressed by normal blood B cells, indicating that CLL B cells express IgH that are distinctive from those found in the normal adult blood B cell repertoire.
Cutting Edge: FISP (IL-4-Induced Secreted Protein), a Novel Cytokine-Like Molecule Secreted by Th2 Cells
Authors: Schaefer Gabriele , Venkataraman Chandrasekar , Schindler Ulrike
Published: April 2014

Th cell subsets, namely Th1 and Th2 cells, play an important role in mounting an immune response against invading pathogens. Several genes are selectively up-regulated during differentiation and effector phases of Th subsets. In this study, we report the identification of a novel cytokine-like molecule designated FISP (IL-4-induced secreted protein), which is selectively expressed and secreted by Th2 cells. Detectable levels of FISP are observed only 3 days after initiation of Th2 differentiation. Expression of FISP in developing Th cells requires at least two signals: TCR signaling involving protein kinase C activation and STAT6-dependent IL-4R signaling.
Cutting Edge: Antigen-Independent CD8 T Cell Proliferation
Authors: Wong Phillip , Pamer Eric G.
Published: April 2014

Recent analyses of CD8 T cell responses to Listeria monocytogenes infection demonstrate that the duration of in vivo T cell proliferation is not determined by the amount or duration of Ag presentation. However, the extent to which T lymphocytes are capable of proliferating in the absence of Ag is unknown. Herein we demonstrate that CD8 T lymphocytes undergo up to eight rounds of proliferation in the absence of Ag following transient, 2.5-h in vitro antigenic stimulation. Ag-independent expansion of CD8 T cells is driven by IL-2 and is further augmented by IL-7 or IL-15. These experiments clearly demonstrate that CD8 T cells undergo prolonged proliferation following transient Ag exposure and support the notion that in vivo CD8 T cell expansion following infection can be uncoupled from Ag presentation.
Cutting Edge: A Single MHC Anchor Residue Alters the Conformation of a Peptide-MHC Complex Inducing T Cells That Survive Negative Selection
Authors: Peterson Daniel A. , DiPaolo Richard J. , Kanagawa Osami , Unanue Emil R.
Published: April 2014

We generated transgenic mice that expressed hen egg-white lysozyme (HEL) under a class II MHC promoter. The A7 line expressed HEL with a point mutation in the Asp52 residue, the main anchor amino acid responsible for the selection of the chemically dominant family of peptides (52–60) by I-Ak molecules. Mice expressing HEL with Ala52 were completely unresponsive when immunized with the same protein, i.e., HEL A52. However, the same mice immunized with wild-type HEL elicited T cells that recognized a conformation of the 52–61 core sequence uniquely different between Asp52 and Ala52 containing peptides. Importantly, some T cells also recognized the HEL A52 peptide given exogenously but not the same peptide processed from HEL A52 protein. Thus, a core MHC anchor residue influences markedly the specificity of the T cells. We discuss the relevance of these findings to autoimmunity and vaccination with altered peptides.
Cutting Edge: Systemic Inhibition of Angiogenesis Underlies Resistance to Tumors During Acute Toxoplasmosis
Authors: Hunter Christopher A. , Yu Duonan , Gee Michael , Ngo Cam V. , Sevignani Cinzia , Goldschmidt Michael , Golovkina Tatyana V. , Evans Sydney , Lee William F. , Thomas-Tikhonenko Andrei
Published: April 2014

The ability of various infections to suppress neoplastic growth has been well documented. This phenomenon has been traditionally attributed to infection-induced concomitant, cell-mediated antitumor immunity. We found that infection with Toxoplasma gondii effectively blocked neoplastic growth of a nonimmunogenic B16.F10 melanoma. Moreover, this effect was independent of cytotoxic T or NK cells, production of NO by macrophages, or the function of the cytokines IL-12 and TNF-α. These findings suggested that antitumor cytotoxicity was not the primary mechanism of resistance. However, infection was accompanied by strong, systemic suppression of angiogenesis, both in a model system and inside the nascent tumor. This suppression resulted in severe hypoxia and avascular necrosis that are incompatible with progressive neoplastic growth. Our results identify the suppression of tumor neovascularization as a novel mechanism critical for infection-induced resistance to tumors.
Human Dendritic Cells Are Activated by Chimeric Human Papillomavirus Type-16 Virus-Like Particles and Induce Epitope-Specific Human T Cell Responses In Vitro
Authors: Rudolf Michael P. , Fausch Steven C. , Da Silva Diane M. , Kast W. Martin
Published: April 2014

Human papillomavirus (HPV)-derived chimeric virus-like particles (VLPs) are the leading candidate vaccine for the treatment or prevention of cervical cancer in humans. Dendritic cells (DCs) are the most potent inducers of immune responses and here we show for the first time evidence for binding of chimeric HPV-16 VLPs to human peripheral blood-derived DCs. Incubation of immature human DCs with VLPs for 48 h induced a significant up-regulation of the CD80 and CD83 molecules as well as secretion of IL-12. Confocal microscopy analysis revealed that cell surface-bound chimeric VLPs were taken up by DCs. Moreover, DCs loaded with chimeric HPV-16 L1L2-E7 VLPs induced an HLA-*0201-restricted human T cell response in vitro specific for E7-derived peptides. These results clearly demonstrate that immature human DCs are fully activated by chimeric HPV-16 VLPs and subsequently are capable of inducing endogenously processed epitope-specific human T cell responses in vitro. Overall, these findings could explain the high immunogenicity and efficiency of VLPs as vaccines.
Distinct BMI-1 and EZH2 Expression Patterns in Thymocytes and Mature T Cells Suggest a Role for Polycomb Genes in Human T Cell Differentiation
Authors: Raaphorst Frank M. , Otte Arie P. , van Kemenade Folkert J. , Blokzijl Tjasso , Fieret Elly , Hamer Karien M. , Satijn David P. E. , Meijer Chris J. L. M.
Published: April 2014

BMI-1 and EZH2 Polycomb-group (PcG) proteins belong to two distinct protein complexes involved in the regulation of hematopoiesis. Using unique PcG-specific antisera and triple immunofluorescence, we found that mature resting peripheral T cells expressed BMI-1, whereas dividing blasts were EZH2+. By contrast, subcapsular immature double-negative (DN) (CD4−/CD8−) T cells in the thymus coexpressed BMI-1 and EZH2 or were BMI-1 single positive. Their descendants, double-positive (DP; CD4+/CD8+) cortical thymocytes, expressed EZH2 without BMI-1. Most EZH2+ DN and DP thymocytes were dividing, while DN BMI-1+/EZH2− thymocytes were resting and proliferation was occasionally noted in DN BMI-1+/EZH2+ cells. Maturation of DP cortical thymocytes to single-positive (CD4+/CD8− or CD8+/CD4−) medullar thymocytes correlated with decreased detectability of EZH2 and continued relative absence of BMI-1. Our data show that BMI-1 and EZH2 expression in mature peripheral T cells is mutually exclusive and linked to proliferation status, and that this pattern is not yet established in thymocytes of the cortex and medulla. T cell stage-specific PcG expression profiles suggest that PcG genes contribute to regulation of T cell differentiation. They probably reflect stabilization of cell type-specific gene expression and irreversibility of lineage choice. The difference in PcG expression between medullar thymocytes and mature interfollicular T cells indicates that additional maturation processes occur after thymocyte transportation from the thymus.
A Requirement for IL-2/IL-2 Receptor Signaling in Intrathymic Negative Selection
Authors: Bassiri Hamid , Carding Simon R.
Published: April 2014

The nature of the signals that influence thymocyte selection and determine the fate of CD4+8+ (double positive) thymocytes remains unclear. Cytokines produced locally in the thymus may modulate signals delivered by TCR-MHC/peptide interactions and thereby influence the fate of double-positive thymocytes. Because the IL-2/IL-2R signaling pathway has been implicated in thymocyte and peripheral T cell survival, we investigated the possibility that IL-2/IL-2R interactions contribute to the deletion of self-reactive, Ag-specific thymocytes. By using nontransgenic and transgenic IL-2-sufficient and -deficient animal model systems, we have shown that during TCR-mediated thymocyte apoptosis, IL-2 protein is expressed in situ in the thymus, and apoptotic thymocytes up-regulate expression of IL-2Rs. IL-2R+ double-positive and CD4 single-positive thymocytes undergoing activation-induced cell death bind and internalize IL-2. IL-2-deficient thymocytes are resistant to TCR/CD3-mediated apoptotic death, which is overcome by providing exogenous IL-2 to IL-2−/− mice. Furthermore, disruption or blockade of IL-2/IL-2R interactions in vivo during Ag-mediated selection rescues some MHC class II-restricted thymocytes from apoptosis. Collectively, these findings provide evidence for the direct involvement of the IL-2/IL-2R signaling pathway in the deletion of Ag-specific thymocyte populations and suggest that CD4 T cell hyperplasia and autoimmunity in IL-2−/− mice is a consequence of ineffective deletion of self-reactive T cells.
Inhibition of Antigen-Induced Mediator Release from IgE-Sensitized Cells by a Monoclonal Anti-FcεRI α-Chain Receptor Antibody: Implications for the Involvement of the Membrane-Proximal α-Chain Region in FcεRI-Mediated Cell Activation
Authors: Nechansky Andreas , Robertson Michael W. , Albrecht Bettina A. , Apgar John R. , Kricek Franz
Published: April 2014

The interaction between human IgE and its high affinity receptor, FcεRI, is a critical event in mediating the allergic response. Aggregation of the α-chain of FcεRI (FcεRIα) occurs via cross-linking of receptor-bound IgE by Ag, resulting in cell activation and the release of mediators of hypersensitivity. Recently, we mapped the epitopes of two anti-FcεRIα mAbs, 15/1 and 5H5F8. In contrast to 15/1, mAb 5H5F8 does not inhibit IgE binding to FcεRIα. Here we demonstrate both 5H5F8 binding to FcεRI+ cells as well as a high level of IgE binding to 5H5F8-saturated cells. At the same time 5H5F8 strongly inhibits hexosaminidase release and Ca2+ flux after Ag triggering from human IgE-sensitized RBL-2H3 cells stably transfected with human FcεRIα. Further, 5H5F8 and its Fab inhibit sulfidoleukotriene and histamine release from primary human peripheral blood leukocytes, including cells bearing endogenous IgE. Furthermore, we confirm that 5H5F8 maps to a linear peptide sequence in close proximity to the cell membrane. Two chemically synthesized peptides containing the 5H5F8 epitope sequence PREKY were selected for detailed analysis of 5H5F8 and 5H5F8 Fab binding and were found to produce Kd values of similar magnitude to that observed for binding to recombinant FcεRIα. These peptides may prove useful as targets for the identification of antagonists of FcεRIα-mediated biological activity. Moreover, our data indicate that FcεRIα-mediated activation may involve a novel α-chain epitope in an early step of the cell-triggering pathway leading to cellular activation.
Histamine Induces CD86 Expression and Chemokine Production by Human Immature Dendritic Cells
Authors: Caron Gersende , Delneste Yves , Roelandts Edith , Duez Catherine , Herbault Nathalie , Magistrelli Giovanni , Bonnefoy Jean-Yves , Pestel Joel , Jeannin Pascale
Published: April 2014

Mast cells and immature dendritic cells (DC) are in close contact in peripheral tissues. Upon activation, mast cells release histamine, a mediator involved in the immediate hypersensitivity reaction. We therefore tested whether histamine could affect human DC activation and maturation. Histamine induces CD86 expression on immature DC in a dose-dependent (significant at 10−7 M) and transient manner (maximal after 24-h stimulation). Histamine also transiently up-regulates the expression of the costimulatory and accessory molecules, CD40, CD49d, CD54, CD80, and MHC class II. As a consequence, immature DC exposed for 24 h to histamine stimulate memory T cells more efficiently than untreated DC. In addition, histamine induces a potent production of IL-6, IL-8, monocyte chemoattractant protein 1, and macrophage-inflammatory protein 1α by immature DC and also up-regulates IL-1β, RANTES, and macrophage-inflammatory protein 1β but not TNF-α and IL-12 mRNA expression. Histamine activates immature DC through both the H1 and H2 receptors. However, histamine-treated DC do not have a phenotype of fully mature cells, as they do neither show significant changes in the expression of the chemokine receptors, CCR5, CCR7 and CXC chemokine receptor 4, nor expression of CD83 de novo. These data demonstrate that histamine activates immature DC and induces chemokine production, thereby suggesting that histamine, via stimulation of resident DC, may participate locally in T cell stimulation and in the late inflammatory reaction associated with allergic disorders.
Signaling Through MHC Class II Molecules Blocks CD95-Induced Apoptosis
Authors: Catlett Ian M. , Xie Ping , Hostager Bruce S. , Bishop Gail A.
Published: April 2014

B cells are induced to express CD95 upon interaction with T cells. This interaction renders the B cells sensitive to CD95-mediated apoptosis, but ligation of proviability surface receptors is able to inhibit apoptosis induction. MHC class II is a key molecule required for Ag presentation to Th cells, productive T cell-B cell interaction, and B cell activation. We demonstrate here for the first time that MHC class II ligation also confers a rapid resistance to CD95-induced apoptosis, an affect that does not require de novo protein synthesis. Signaling through class II molecules blocks the activation of caspase 8, but does not affect the association of CD95 and Fas-associated death domain-containing protein. MHC class II ligation thus blocks proximal signaling events in the CD95-mediated apoptotic pathway.
Requirement for a Complex Array of Costimulators in the Negative Selection of Autoreactive Thymocytes In Vivo
Authors: Li Ruixia , Page Dawne M.
Published: April 2014

Autoreactive thymocytes can be deleted at an immature stage of their development by Ag-induced apoptosis or negative selection. In addition to Ag, negative selection also requires costimulatory signals from APC. We recently used a fetal thymus organ culture system to show that CD5, CD28, and TNF cooperatively regulate deletion of autoreactive thymocytes. Although these experiments provided strong evidence for the action of several costimulators in negative selection, we wished to demonstrate a role for these molecules in a physiologically natural model where thymocytes are deleted in vivo by endogenously expressed Ags. Accordingly, we examined thymocyte deletion in costimulator-null mice in three models of autoantigen-induced negative selection. We compared CD5−/− CD28−/− mice to CD40L−/− mice, which exhibited a profound block in negative selection in all three systems. Surprisingly, only one of the three models revealed a requirement for the CD5 and CD28 costimulators in autoantigen-induced deletion. These results suggest that an extraordinarily complex array of costimulators is involved in negative selection. We predict that different sets of costimulators will be required depending on the timing of negative selection, the Ag, the signal strength, the APC, and whether Ag presentation occurs on class I or class II MHC molecules.
Role for Transcription Pax5A Factor in Maintaining Commitment to the B Cell Lineage by Selective Inhibition of Granulocyte-Macrophage Colony-Stimulating Factor Receptor Expression
Authors: Chiang Mark Y. , Monroe John G.
Published: April 2014

During early B lymphopoiesis, developing B cells maintain lineage commitment despite the local presence of myeloid lineage-promoting cytokines such as GM-CSF and IL-3. Previous observations suggest that the B cell-specific transcription factor Pax5A (paired box 5A transcription factor) plays a role in maintaining B cell lineage commitment by limiting expansion and survival of early IL-3/GM-CSF-dependent myeloid lineage cells. To define a mechanism by which Pax5A can exert these inhibitory effects on myeloid lineage differentiation, an inducible form of the Pax5A protein was expressed in the myeloid cell line FDC-P1. This cell line models myeloid progenitors in that it responds to the survival and growth-potentiating effects of IL-3 and GM-CSF. We observed that enforced expression of Pax5A selectively suppressed proliferation in response to GM-CSF, but not IL-3. This effect was associated with specific down-regulation of GM-CSFR α-chain, but not β-chain expression. These data provide a molecular mechanism to enforce commitment to the B cell lineage despite the presence of GM-CSF, a factor that has been shown to convert early developing B cells to the myeloid lineage. Furthermore, they indicate a role for B cell Pax5A expression in maintaining rather than directing commitment to the B cell lineage.
Cell-Associated Ovalbumin Is Cross-Presented Much More Efficiently than Soluble Ovalbumin In Vivo
Authors: Li Ming , Davey Gayle M. , Sutherland Robyn M. , Kurts Christian , Lew Andrew M. , Hirst Claire , Carbone Francis R. , Heath William R.
Published: April 2014

To better understand the antigenic requirements for cross-presentation, we compared the in vivo efficiency of presentation of cell-associated vs soluble OVA with the OT-I (CD8) and OT-II (CD4) TCR transgenic lines. Cross-presentation of cell-associated OVA was very efficient, requiring as little as 21 ng of OVA to activate OT-II cells and 100-fold less to activate OT-I cells. In contrast, soluble OVA was presented inefficiently, requiring at least 10,000 ng OVA for activation of either T cell subset. Thus, cell-associated OVA was presented 500-fold more efficiently than soluble OVA to CD4 T cells and 50,000-fold more efficiently to CD8 T cells. These data, which represent the first quantitative in vivo analysis of cross-presentation, show that cell-associated OVA is very efficiently presented via the class I pathway.
Stage-Specific Modulation of IFN-Regulatory Factor 4 Function by Krüppel-Type Zinc Finger Proteins
Authors: Gupta Sanjay , Anthony Alissa , Pernis Alessandra B.
Published: April 2014

Optimal humoral responses depend on the activation of Ag-specific B cells, followed by their progression toward a fully differentiated phenotype. Acquisition of stage-appropriate patterns of gene expression is crucial to this differentiation program. However, the molecular mechanisms used by B cells to modulate gene expression as they complete their maturation program are poorly understood. IFN-regulatory factor 4 (IRF-4) plays a critical role in mature B cell function. Using the transcriptional regulation of the human B cell activation marker CD23 as a model system, we have previously demonstrated that IRF-4 is induced in response to B cell-activating stimuli and that it acts as a transactivator of CD23 gene expression. We have furthermore found that IRF-4 function can be blocked by B cell lymphomas 6 (BCL-6) protein, a Krüppel-type zinc finger repressor normally expressed in germinal center B cells. However, CD23 expression is known to be down-regulated in plasma cells despite high level expression of IRF-4 and the lack of BCL-6, suggesting that in plasma cells the IRF-4-mediated induction of CD23 is prevented by its interaction with a distinct repressor. In this set of studies, we demonstrate that IRF-4 interacts with B lymphocyte-induced maturation protein/positive regulatory domain I-binding factor 1 (Blimp1/PRD1-BF1), a Krüppel-type zinc finger protein whose expression correlates with terminal B cell differentiation. Functional studies indicate that Blimp1, like BCL-6, can block IRF-4-transactivating ability. These findings thus support a model whereby IRF-4 function is modulated in a stage-specific manner by its interaction with developmentally restricted sets of Krüppel-type zinc finger proteins.
Increasing the Affinity for Tumor Antigen Enhances Bispecific Antibody Cytotoxicity
Authors: McCall Adrian M. , Shahied Lillian , Amoroso Anne R. , Horak Eva M. , Simmons Heidi H. , Nielson Ulrick , Adams Gregory P. , Schier Robert , Marks James D. , Weiner Louis M.
Published: April 2014

We tested the hypothesis that bispecific Abs (Bsab) with increased binding affinity for tumor Ags augment retargeted antitumor cytotoxicity. We report that an increase in the affinity of Bsab for the HER2/neu Ag correlates with an increase in the ability of the Bsab to promote retargeted cytotoxicity against HER2/neu-positive cell lines. A series of anti-HER2/neu extracellular domain-directed single-chain Fv fragments (scFv), ranging in affinity for HER2/neu from 10−7 to 10−11 M, were fused to the phage display-derived NM3E2 human scFv. NM3E2 associates with the extracellular domain of human FcγRIII (CD16). The resulting series of Bsab promoted cytotoxicity of SKOV3 human ovarian carcinoma cells overexpressing HER2/neu by human PBMC preparations containing CD16-positive NK cells. The affinity for HER2/neu clearly influenced the ability of the Bsab to promote cytotoxicity of 51Cr-labeled SKOV3 cells. Lysis was 6.5% with an anti-HER2/neu KD = 1.7 × 10−7 M, 14.5% with KD = 5.7 × 10−9 M, and 21.3% with KD = 1.7 × 10−10 M at 50:1 E:T ratios. These scFv-based Bsab did not cross-link receptors and induce leukocyte calcium mobilization in the absence of tumor cell engagement. Thus, these novel Bsab structures should not induce the dose-limiting cytokine release syndromes that have been observed in clinical trials with intact IgG Bsab. Additional manipulations in Bsab structure that improve selective tumor retention or facilitate the ability of Bsab to selectively cross-link tumor and effector cells at tumor sites should further improve the utility of this therapeutic strategy.
Lupus Antibody Bivalency Is Required to Enhance Prothrombin Binding to Phospholipid
Authors: Field Susan L. , Chesterman Colin N. , Dai Yan-Ping , Hogg Philip J.
Published: April 2014

Lupus anticoagulants (LA) are a family of autoantibodies that are associated with in vitro anticoagulant activity but a strong predisposition to in vivo thrombosis. They are directed against plasma phospholipid-binding proteins including prothrombin. We have proposed that LA propagates coagulation in flowing blood by facilitating prothrombin interaction with the damaged blood vessel wall. A murine monoclonal anti-prothrombin Ab and three of three LA IgGs enhanced prothrombin binding to 75:25 phosphatidyl choline:phosphatidyl serine vesicles measured by either ultracentrifugation or right-angle light scattering. The assembly of prothrombin and LA IgG on phospholipid vesicles was estimated by surface plasmon resonance. The on rates for prothrombin and LA IgG were approximately the same as the on rate for prothrombin alone. In contrast, the off rates for prothrombin and LA IgG were 2- to 3-fold slower than the off rate for prothrombin. LA IgG bivalency was required for enhanced prothrombin binding to phospholipid vesicles, as Fab of the LA IgGs did not influence prothrombin binding at concentrations up to 40 μM. Modeling of the interactions of prothrombin, LA IgG and phospholipid vesicles indicated that augmentation of prothrombin binding to phospholipid vesicles by LA IgG could be accounted for by the bivalency of the LA IgG and the elevated microenvironmental concentration of prothrombin on the surface of phospholipid vesicles.
Fundamental Ca2+ Signaling Mechanisms in Mouse Dendritic Cells: CRAC Is the Major Ca2+ Entry Pathway
Authors: Hsu Shyue-fang , O’Connell Peta J. , Klyachko Vitaly A. , Badminton Michael N. , Thomson Angus W. , Jackson Meyer B. , Clapham David E. , Ahern Gerard P.
Published: April 2014

Although Ca2+-signaling processes are thought to underlie many dendritic cell (DC) functions, the Ca2+ entry pathways are unknown. Therefore, we investigated Ca2+-signaling in mouse myeloid DC using Ca2+ imaging and electrophysiological techniques. Neither Ca2+ currents nor changes in intracellular Ca2+ were detected following membrane depolarization, ruling out the presence of functional voltage-dependent Ca2+ channels. ATP, a purinergic receptor ligand, and 1–4 dihydropyridines, previously suggested to activate a plasma membrane Ca2+ channel in human myeloid DC, both elicited Ca2+ rises in murine DC. However, in this study these responses were found to be due to mobilization from intracellular stores rather than by Ca2+ entry. In contrast, Ca2+ influx was activated by depletion of intracellular Ca2+ stores with thapsigargin, or inositol trisphosphate. This Ca2+ influx was enhanced by membrane hyperpolarization, inhibited by SKF 96365, and exhibited a cation permeability similar to the Ca2+ release-activated Ca2+ channel (CRAC) found in T lymphocytes. Furthermore, ATP, a putative DC chemotactic and maturation factor, induced a delayed Ca2+ entry with a voltage dependence similar to CRAC. Moreover, the level of phenotypic DC maturation was correlated with the extracellular Ca2+ concentration and enhanced by thapsigargin treatment. These results suggest that CRAC is a major pathway for Ca2+ entry in mouse myeloid DC and support the proposal that CRAC participates in DC maturation and migration.
The Exon A (C77G) Mutation Is a Common Cause of Abnormal CD45 Splicing in Humans
Authors: Tchilian Elma Z. , Wallace Diana L. , Imami Nesrina , Liao Hua-Xin , Burton Catherine , Gotch Frances , Martinson Jeremy , Haynes Barton F. , Beverley Peter C. L.
Published: April 2014

The leukocyte common (CD45) Ag is essential for normal T lymphocyte function and alternative splicing at the N terminus of the gene is associated with changes in T cell maturation and differentiation. Recently, a statistically significant association was reported in a large series of human thymus samples between phenotypically abnormal CD45 splicing and the presence of the CC chemokine receptor 5 deletion 32 (CCR5del32) allele, which confers resistance to HIV infection in homozygotes. We show here that abnormal splicing in these thymus samples is associated with the presence of the only established cause of CD45 abnormal splicing, a C77G transversion in exon A. In addition we have examined 227 DNA samples from peripheral blood of healthy donors and find no association between the exon A (C77G) and CCR5del32 mutations. Among 135 PBMC samples, tested by flow cytometric analysis, all those exhibiting abnormal splicing of CD45 also showed the exon A C77G transversion. We conclude that the exon A (C77G) mutation is a common cause of abnormal CD45 splicing and that further disease association studies of this mutation are warranted.
A Prominent Role for Activator Protein-1 in the Transcription of the Human 2B4 (CD244) Gene in NK Cells
Authors: Chuang Samuel S. , Pham Hoang-Tuan K. , Kumaresan Pappanaicken R. , Mathew Porunelloor A.
Published: April 2014

The cell surface glycoprotein 2B4 (CD244) of the Ig superfamily is involved in the regulation of NK and T lymphocyte functions. We have recently identified CD48 as the high affinity counterreceptor for 2B4 in both mice and humans. The cytoplasmic domain of 2B4 associates with src homology 2 domain-containing protein or signaling lymphocyte activation molecule-associated protein, whose mutation is the underlying genetic defect in the X-linked lymphoproliferative syndrome. In this study, we report the molecular cloning and characterization of the human 2B4 (h2B4) promoter. Through primer extension analysis, we found that the transcription of the h2B4 gene initiates at multiple start sites. We isolated h2B4 genomic clones and PCR amplified the 5′ untranslated region containing the promoter elements. We have identified a functional AP-1 site that lies between (−106 to −100) through transient transfection analysis in YT cells, a human NK cell line. EMSAs with Abs specific for various protein factors of the AP-1 family revealed that multiple members of the Jun family are involved in the regulation of the h2B4 gene. Mutation of the AP-1 site not only abolishes protein/DNA interactions but also promoter activity. These results demonstrate a significant role for AP-1 in the transcriptional regulation of the h2B4 gene.
Culture at High Density Improves the Ability of Human Macrophages to Control Mycobacterial Growth
Authors: Boechat Neio , Bouchonnet Francine , Bonay Marcel , Grodet Alain , Pelicic Vladimir , Gicquel Brigitte , Hance Allan J.
Published: April 2014

The mechanisms through which granuloma formation helps control mycobacterial infection are poorly understood, but it is possible that the accumulation of macrophages at high density at sites of infection promotes the differentiation of macrophages into cells with improved mycobactericidal activity. To test this possibility, varying numbers of monocytes were cultured in 96-well plates for 3 days, infected with Mycobacterium bovis bacillus Calmette-Guérin, and mycobacterial number was assessed 7 days after infection based on the measurement of luciferase activity expressed by a mycobacterial reporter strain or by counting CFU. Mycobacterial growth was optimal in cultures containing 5 × 104 cells/well, but increasing the number of cells to 2 × 105 cells/well resulted in complete inhibition of mycobacterial growth. This effect could not be explained by differences in mycobacterial uptake, multiplicity of infection, acidification of the extracellular medium in high density cultures, enhanced NO production, or paracrine stimulation resulting from secretion of cytokines or other proteins. The morphology of cells cultured at high density was strikingly different from that of monocytes cultured at 5 × 104 cells/well, including the appearance of numerous giant cells. The bacteriostatic activity of monocyte-derived macrophages was also dependent on cell number, but fewer of these more mature cells were required to control mycobacterial growth. Thus, the ability of human macrophages to control mycobacterial infection in vitro is influenced by the density of cells present, findings that may help explain why the formation of granulomas in vivo appears to be a key event in the control of mycobacterial infections.
Vaccination with the T Cell Antigen Mtb 8.4 Protects Against Challenge withMycobacterium tuberculosis
Authors: Coler Rhea N. , Campos-Neto Antonio , Ovendale Pamela , Day Fiona H. , Fling Steven P. , Zhu Liqing , Serbina Natalya , Flynn JoAnne L. , Reed Steven G. , Alderson Mark R.
Published: April 2014

The development of an effective vaccine against Mycobacterium tuberculosis is a research area of intense interest. Mounting evidence suggests that protective immunity to M. tuberculosis relies on both MHC class II-restricted CD4+ T cells and MHC class I-restricted CD8+ T cells. By purifying polypeptides present in the culture filtrate of M. tuberculosis and evaluating these molecules for their ability to stimulate PBMC from purified protein derivative-positive healthy individuals, we previously identified a low-m.w. immunoreactive T cell Ag, Mtb 8.4, which elicited strong Th1 T cell responses in healthy purified protein derivative-positive human PBMC and in mice immunized with recombinant Mtb 8.4. Herein we report that Mtb 8.4-specific T cells can be detected in mice immunized with the current live attenuated vaccine, Mycobacterium bovis-bacillus Calmette-Guérin as well as in mice infected i.v. with M. tuberculosis. More importantly, immunization of mice with either plasmid DNA encoding Mtb 8.4 or Mtb 8.4 recombinant protein formulated with IFA elicited strong CD4+ T cell and CD8+ CTL responses and induced protection on challenge with virulent M. tuberculosis. Thus, these results suggest that Mtb 8.4 is a potential candidate for inclusion in a subunit vaccine against TB.