bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of N-Formyl Peptide-Mediated Degranulation by Receptor Phosphorylation
Authors: Vines Charlotte M. , Xue Mei , Maestas Diane C. , Cimino Daniel F. , Prossnitz Eric R. 
Published: April 2014

Abstract
One of the major functions of the N-formyl peptide receptor (FPR) is to mediate leukocyte degranulation. Phosphorylation of the C-terminal domain of the FPR is required for receptor internalization and desensitization. Although arrestins mediate phosphorylation-dependent desensitization, internalization, and initiation of novel signaling cascades for a number of G protein-coupled receptors, their roles in FPR regulation and signaling remain unclear. CXCR1-mediated degranulation of RBL-2H3 cells is promoted by arrestin binding. To determine whether receptor phosphorylation or arrestin binding is required to promote FPR-mediated degranulation, we used RBL-2H3 cells stably transfected with either the wild-type FPR or a mutant form, ΔST, which is incapable of undergoing ligand-stimulated phosphorylation. We observed that stimulation of wild-type FPR resulted in very low levels of degranulation compared with that mediated by cross-linking of the FcεRI receptor. Stimulation of the ΔST mutant, however, resulted in levels of degranulation comparable to those of the FcεRI receptor, demonstrating that neither receptor phosphorylation nor arrestin binding was necessary to initiate FPR-mediated degranulation. Degranulation initiated by the ΔST mutant was proportional to the level of active cell surface receptor, suggesting that either receptor internalization or desensitization may be responsible for terminating degranulation of the wild-type FPR. To distinguish between these possibilities, we used a partially phosphorylation-deficient mutant of the FPR that can undergo internalization, but not desensitization. Degranulation by this mutant FPR was indistinguishable from that of the ΔST mutant, indicating that FPR phosphorylation or binding of arrestin but not internalization terminates the degranulation response.
Lyn and Syk Kinases Are Sequentially Engaged in Phagocytosis Mediated by FcγR
Authors: Strzelecka-Kiliszek Agnieszka , Kwiatkowska Katarzyna , Sobota Andrzej 
Published: April 2014

AbstractRecent data indicate that phagocytosis mediated by FcγRs is controlled by the Src and Syk families of protein tyrosine kinases. In this study, we demonstrate a sequential involvement of Lyn and Syk in the phagocytosis of IgG-coated particles. The particles isolated at the stage of their binding to FcγRs (4°C) were accompanied by high amounts of Lyn, in addition to the signaling γ-chain of FcγRs. Simultaneously, the particle binding induced rapid tyrosine phosphorylation of numerous proteins. During synchronized internalization of the particles induced by shifting the cell to 37°C, Syk kinase and Src homology 2-containing tyrosine phosphatase-1 (SHP-1) were associated with the formed phagosomes. At this step, most of the proteins were dephosphorylated, although some underwent further tyrosine phosphorylation. Quantitative immunoelectron microscopy studies confirmed that Lyn accumulated under the plasma membrane beneath the bound particles. High amounts of the γ-chain and tyrosine-phosphorylated proteins were also observed under the bound particles. When the particles were internalized, the γ-chain was still detected in the region of the phagosomes, while amounts of Lyn were markedly reduced. In contrast, the vicinity of the phagosomes was heavily decorated with anti-Syk and anti-SHP-1 Abs. The local level of protein tyrosine phosphorylation was reduced. The data indicate that the accumulation of Lyn during the binding of IgG-coated particles to FcγRs correlated with strong tyrosine phosphorylation of numerous proteins, suggesting an initiating role for Lyn in protein phosphorylation at the onset of the phagocytosis. Syk kinase and SHP-1 phosphatase are mainly engaged at the stage of particle internalization.
WY14,643, a PPARα Ligand, Has Profound Effects on Immune Responses In Vivo
Authors: Cunard Robyn , DiCampli Dennis , Archer D. Clay , Stevenson Jennifer L. , Ricote Mercedes , Glass Christopher K. , Kelly Carolyn J. 
Published: April 2014

Abstract
Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors with diverse actions. PPARα and PPARγ are expressed in different lymphocyte subpopulations. Recently, we have observed that PPARα ligands elicit augmented IL-4 expression in cultures of mitogen-activated splenocytes. The following studies were undertaken to characterize the in vivo effects of WY14,643, a PPARα ligand. Our studies demonstrate that oral administration of WY14,643 markedly reduces splenocyte number in immunized and nonimmunized C57BL/6 mice. Mice fed WY14,643 display impaired IgG responses to myelin oligodendrocyte glycoprotein peptide 35–55 (pMOG35–55), following immunization with pMOG35–55/CFA. Following in vitro restimulation with pMOG35–55, splenocytes harvested from WY14,643-fed mice demonstrate impaired production of IFN-γ, IL-6, and TNF-α despite similar proliferative responses. We also demonstrate higher expression of PPARα in B than T cells. Finally, to obtain an understanding of the cause of splenocyte depletion with fibrate therapy, we studied the effect of WY14,643 on apoptosis of activated splenocytes. WY14,643 in vitro induces apoptosis in lymphocytes and this effect appears to occur in a PPARα-independent manner. Thus WY14,643, a fibrate, is a profound immunosuppressive agent.
Peroxisome Proliferator-Activated Receptor γ-Mediated NF-κB Activation and Apoptosis in Pre-B Cells
Authors: Schlezinger Jennifer J. , Jensen Brenda A. , Mann Koren K. , Ryu Heui-Young , Sherr David H. 
Published: April 2014

Abstract
The role of peroxisome proliferator-activated receptor γ (PPARγ) in adipocyte physiology has been exploited for the treatment of diabetes. The expression of PPARγ in lymphoid organs and its modulation of macrophage inflammatory responses, T cell proliferation and cytokine production, and B cell proliferation also implicate it in immune regulation. Despite significant human exposure to PPARγ agonists, little is known about the consequences of PPARγ activation in the developing immune system. Here, well-characterized models of B lymphopoiesis were used to investigate the effects of PPARγ ligands on nontransformed pro/pre-B (BU-11) and transformed immature B (WEHI-231) cell development. Treatment of BU-11, WEHI-231, or primary bone marrow B cells with PPARγ agonists (ciglitazone and GW347845X) resulted in rapid apoptosis. A role for PPARγ and its dimerization partner, retinoid X receptor (RXR)α, in death signaling was supported by 1) the expression of RXRα mRNA and cytosolic PPARγ protein, 2) agonist-induced binding of PPARγ to a PPRE, and 3) synergistic increases in apoptosis following cotreatment with PPARγ agonists and 9-cis-retinoic acid, an RXRα agonist. PPARγ agonists activated NF-κB (p50, Rel A, c-Rel) binding to the upstream κB regulatory element site of c-myc. Only doses of agonists that induced apoptosis stimulated NF-κB-DNA binding. Cotreatment with 9-cis-retinoic acid and PPARγ agonists decreased the dose required to activate NF-κB. These data suggest that activation of PPARγ-RXR initiates a potent apoptotic signaling cascade in B cells, potentially through NF-κB activation. These results have implications for the nominal role of the PPARγ in B cell development and for the use of PPARγ agonists as immunomodulatory therapeutics.
The Roles of IL-12 in Providing a Third Signal for Clonal Expansion of Naive CD8 T Cells
Authors: Valenzuela Javier , Schmidt Clint , Mescher Matthew 
Published: April 2014

AbstractStimulation of an effective in vitro or in vivo response by naive CD8 T cells requires three signals: TCR engagement, costimulation/IL-2, and a third signal that can be provided by IL-12. In addition to being required for acquisition of cytolytic function, IL-12 is required for optimal IL-2-dependent proliferation and clonal expansion. In experiments examining in vitro stimulation of naive CD8 T cells, IL-12 is shown to stimulate expression of the IL-2R α-chain (CD25) to much higher levels than are reached in response to just TCR and costimulation and/or IL-2. In addition, high CD25 expression is substantially prolonged in the presence of IL-12. As a consequence, the cells proliferate more effectively in response to low levels of IL-2. Examination of adoptively transferred TCR transgenic CD8 T cells responding to peptide Ag confirmed that IL-12 up-regulates CD25 in vivo, even when B7-mediated costimulation is largely blocked. TCR- and IL-2-dependent proliferation of CD8 T cells from mice deficient in CD25 was also found to increase in the presence of IL-12, indicating that CD25 up-regulation is not the only mechanism by which IL-12 increases clonal expansion of the cells. IL-2 and IL-12 both act to increase expression of both CD25 and the IL-12R, thus providing positive cross-regulation of receptor expression. These results suggest that when cross-priming dendritic cells present class I/Ag and costimulatory ligands, and produce IL-12, naive CD8 T cells will begin to produce IL-2 and both receptors will be optimally up-regulated to insure that an effective response is generated.
B Cell Selection and Affinity Maturation During an Antibody Response in the Mouse with Limited B Cell Diversity
Authors: Kanayama Naoki , Kimoto Takafumi , Todo Kagefumi , Nishikawa Yumiko , Hikida Masaki , Magari Masaki , Cascalho Marilia , Ohmori Hitoshi 
Published: April 2014

AbstractThe quasi-monoclonal mouse has limited B cell diversity, whose major (∼80%) B cell Ag receptors are comprised of the knockin VH 17.2.25 (VHT)-encoded H chain and the λ1 or λ2 L chain, thereby being specific for 4-hydroxy-3-nitrophenylacetyl. The p-nitrophenylacetyl (pNP) was found to be a low affinity analog of nitrophenylacetyl. We examined affinity maturation of anti-pNP IgG by analyzing mAbs obtained from quasi-monoclonal mice that were immunized with this low affinity Ag. The results are: 1) Although VHT/λ1 and VHT/λ2 IgM were equally produced, VHT/λ2 IgG almost exclusively underwent affinity maturation toward pNP. 2) A common mutation in complementarity-determining region 3 of VHT (T313A) mainly contributed to generating the specificity for pNP. 3) Because mutated VHT-encoded γ-chains could form λ1-bearing IgG in Chinese hamster ovary cells, apparent absence of VHT/λ1 anti-pNP IgG may not be due to the incompatibility between the γ-chains and the λ1-chain, but may be explained by the fact that VHT/λ1 B cells showed 50- to 100-fold lower affinity for pNP than VHT/λ2 B cells. 4) Interestingly, a pNP-specific IgM mAb that shared common mutations including T313A with high affinity anti-pNP IgG was isolated, suggesting that a part of hypermutation coupled with positive selection can occur before isotype switching. Thus, even weak B cell receptor engagement can elicit an IgM response, whereas only B cells that received signals stronger than a threshold may be committed to an affinity maturation process.
Hyperconservation of the Putative Antigen Recognition Site of the MHC Class I-b Molecule TL in the Subfamily Murinae: Evidence That Thymus Leukemia Antigen Is an Ancient Mammalian Gene
Authors: Davis Beckley K. , Cook Richard G. , Rich Robert R. , Rodgers John R. 
Published: April 2014

Abstract“Classical” MHC class I (I-a) genes are extraordinarily polymorphic, but “nonclassical” MHC class I (I-b) genes are monomorphic or oligomorphic. Although diversifying (positive) Darwinian selection is thought to explain the origin and maintenance of MHC class I-a polymorphisms, genetic mechanisms underlying MHC class I-b evolution are uncertain. In one extreme model, MHC class I-b loci are derived by gene duplication from MHC class I-a alleles but rapidly drift into functional obsolescence and are eventually deleted. In this model, extant MHC class I-b genes are relatively young, tend to be dysfunctional or pseudogenic, and orthologies are restricted to close taxa. An alternative model proposed that the mouse MHC class I-b gene thymus leukemia Ag (TL) arose ∼100 million years ago, near the time of the mammalian radiation. To determine the mode of evolution of TL, we cloned TL from genomic DNA of 11 species of subfamily Murinae. Every sample we tested contained TL, suggesting this molecule has been maintained throughout murine evolution. The sequence similarity of TL orthologs ranged from 85–99% and was inversely proportional to taxonomic distance. The sequences showed high conservation throughout the entire extracellular domains with exceptional conservation in the putative Ag recognition site. Our results strengthen the hypotheses that TL has evolved a specialized function and represents an ancient MHC class I-b gene.
HLA-DP4, the Most Frequent HLA II Molecule, Defines a New Supertype of Peptide-Binding Specificity
Authors: Castelli Florence A. , Buhot Cécile , Sanson Alain , Zarour Hassane , Pouvelle-Moratille Sandra , Nonn Céline , Gahery-Ségard Hanne , Guillet Jean-Gérard , Ménez André , Georges Bertrand , Maillère Bernard 
Published: April 2014

AbstractAmong HLA-DP specificities, HLA-DP4 specificity involves at least two molecules, HLA-DPA1*0103/DPB1*0401 (DP401) and HLA-DPA1*0103/DPB1*0402 (DP402), which differ from each other by only three residues. Together, they are present worldwide at an allelic frequency of 20–60% and are the most abundant human HLA II alleles. Strikingly, the peptide-binding specificities of these molecules have never been investigated. Hence, in this study, we report the peptide-binding motifs of both molecules. We first set up a binding assay specific for the immunopurified HLA-DP4 molecules. Using multiple sets of synthetic peptides, we successfully defined the amino acid preferences of the anchor residues. With these assays, we were also able to identify new peptide ligands from allergens and viral and tumor Ags. DP401 and DP402 exhibit very similar patterns of recognition in agreement with molecular modeling of the complexes. Pockets P1 and P6 accommodate the main anchor residues and interestingly contain only two polymorphic residues, β86 and β11, respectively. Both positions are almost dimorphic and thus produce a limited number of pocket combinations. Taken together, our results support the existence of three main binding supertypes among HLA-DP molecules and should significantly contribute to the identification of universal epitopes to be used in peptide-based vaccines for cancer, as well as for allergic or infectious diseases.
L-MBP Is Expressed in Epithelial Cells of Mouse Small Intestine
Authors: Uemura Kazuhide , Saka Masako , Nakagawa Tomoaki , Kawasaki Nobuko , Thiel Steffen , Jensenius Jens Christian , Kawasaki Toshisuke 
Published: April 2014

AbstractThe mannan-binding proteins (L-MBP and S-MBP, also denoted MBL-C and MBL-A), mainly produced in liver and existing in liver and serum, play important roles in the innate immunity against a variety of pathogens. Total RNA from mouse tissues were screened for MBP mRNA by RT-PCR. In addition to liver, S-MBP mRNA was detected in lung, kidney, and testis, and L-MBP mRNA was detected in kidney, thymus, and small intestine. Quantitative RT-PCR revealed that the small intestine is a predominant site of extrahepatic expression of L-MBP. Western blotting with polyclonal Abs against rat L-MBP demonstrated this protein in Triton X-100 extracts of the small intestine obtained from mice that had undergone systemic perfusion. Immunohistochemical staining with an mAb against mouse L-MBP and in situ hybridization revealed that L-MBP is selectively expressed in some villous epithelial cells of the small intestine. These findings suggest that L-MBP plays a role in mucosal innate immunity.
Conservation of CD1 Intracellular Trafficking Patterns Between Mammalian Species
Authors: Dascher Christopher C. , Hiromatsu Kenji , Xiong Xiaowei , Sugita Masahiko , Buhlmann Janet E. , Dodge Ingrid L. , Lee Stella Y. , Roura-Mir Carme , Watts Gerald F. , Roy Christopher J. , Behar Samuel M. , Clemens Daniel L. , Porcelli Steve A. , Brenner Michael B. 
Published: April 2014

Abstract
Dendritic cells (DC) are potent APCs that sample Ags from the surrounding environment and present them to naive T cells using cell surface Ag-presenting molecules. The DC in both lymphoid and nonlymphoid tissues express high levels of CD1, a cell surface glycoprotein capable of presenting lipids and glycolipids to T cells. Distinct group 1 CD1 isoforms (CD1a, -b, -c) in man are known to traffic to different parts of the endocytic system where microbial Ags may be sampled. Guinea pigs are the only known rodent species that express the group 1 CD1 proteins. Therefore, we examined the expression and trafficking of guinea pig CD1 (gpCD1) isoforms on isolated DC. Confocal microscopy using mAbs specific for individual gpCD1 isoforms revealed differential trafficking of two distinct CD1b isoforms within DC. Colocalization of MHC class II was observed with the gpCD1b1 isoform, consistent with localization in the late endosomes of DC. In contrast, the gpCD1b3 isoform lacks an endosomal sorting motif and remains on the cell surface. Following incubation with Mycobacterium tuberculosis lipoarabinomannan, colocalization of endocytosed lipoarabinomannan with the gpCD1b1 isoform was observed but not with the gpCD1b3 isoform, which remained primarily on the cell surface. These data demonstrate that guinea pig DC express CD1 isoforms with unique trafficking patterns that recapitulate the patterns seen for human CD1 isoforms. This suggests evolutionary pressure for a conserved mechanism in mammals that allows CD1 to sample lipid Ags from various subcompartments of the endocytic system.
Cationic Polypeptides Are Required for Antibacterial Activity of Human Airway Fluid
Authors: Cole Alexander M. , Liao Hsiang-I , Stuchlik Olga , Tilan Jason , Pohl Jan , Ganz Tomas 
Published: April 2014

Abstract
In a search for direct evidence leading to the biological relevance of airway secretions in innate host defense, we characterized the antibacterial function of cationic polypeptides within minimally manipulated nasal fluid. In this study, we show that cationic antimicrobial polypeptides are responsible for most of the bactericidal activity of whole nasal fluid. The removal of cationic polypeptides using a cation-exchange resin ablated the activity of nasal fluid against Escherichia coli, Listeria monocytogenes, and Pseudomonas aeruginosa. By using a novel proteomic approach, we identified a dozen cationic peptides and proteins within nasal fluid, all of which either are known antimicrobial polypeptides or have other proposed roles in host defense. Of the three most abundant cationic polypeptides in nasal fluid, lysozyme was more effective than either lactoferrin or secretory leukoprotease inhibitor in restoring the antibacterial activity of the cationic polypeptide-depleted fluid against a mucoid cystic fibrosis isolate of P. aeruginosa.
High Affinity Mimotope of the Polysaccharide Capsule of Cryptococcus neoformans Identified from an Evolutionary Phage Peptide Library
Authors: Beenhouwer David O. , May Rena J. , Valadon Philippe , Scharff Matthew D. 
Published: April 2014

Abstract
Cryptococcus neoformans causes a life-threatening meningoencephalitis in a significant percentage of AIDS patients. Mice immunized with a glycoconjugate vaccine composed of the glucuronoxylomannan (GXM) component of the cryptococcal capsular polysaccharide conjugated to tetanus toxoid (TT) produce Abs that, based on the epitope recognized, can be either protective or nonprotective. Since nonprotective Abs block the efficacy of protective Abs, we are interested in developing a vaccine that would focus the immune response specifically to protective epitopes. Previously, we screened a phage display library with 2H1, a protective anti-GXM mAb, and isolated PA1, a representative peptide that had a Kd of 295 nM for 2H1. Mice immunized with PA1 conjugated to keyhole limpet hemocyanin developed high anti-peptide (1/13,000), but low anti-GXM (maximum, 1/200) titers. We now report our efforts to improve this vaccine by screening a sublibrary with six random amino acids added to either end of the PA1 motif to identify higher affinity peptides. P206.1, a peptide isolated from this sublibrary, had 80-fold higher affinity for 2H1 (Kd = 3.7 nM) than PA1. P206.1 bound protective, but not nonprotective, anti-GXM Abs. Mice immunized with P206.1 conjugated to various carriers did not mount an Ab response to GXM despite developing high anti-peptide titers. However, mice primed with GXM-TT and boosted with P206.1-TT developed significant anti-GXM titers (maximum, 1/180,000). This latter immunization scheme focused the immune response on protective epitopes, since only 2–5% of these titers were directed against nonprotective de-O-acetylated GXM epitopes compared with 20–60% in animals primed and boosted with GXM-TT.
IFN-γ Amplifies IL-6 and IL-8 Responses by Airway Epithelial-Like Cells Via Indoleamine 2,3-Dioxygenase
Authors: van Wissen Matthijs , Snoek Mieke , Smids Barbara , Jansen Henk M. , Lutter René 
Published: April 2014

AbstractRespiratory viral infections increase inflammatory responses to concurrent or secondary bacterial challenges, thereby worsening disease outcome. This potentiation of inflammation is explained at least in part by IFN-γ promoting increased sensitivity to TNF-α and LPS. We sought to determine whether and, if so, how IFN-γ can modulate proinflammatory responses to TNF-α and LPS by epithelial cells, which are key effector cells in the airways. Preincubation of airway epithelial-like NCI-H292 cells with IFN-γ resulted in a hyperresponsive IL-6 and IL-8 production to TNF-α and LPS. The underlying mechanism involved the induction of indoleamine 2,3-dioxygenase, which catabolized the essential amino acid, tryptophan. Depletion of tryptophan led to stabilization of IL-6 and IL-8 mRNA and increased IL-6 and IL-8 responses, whereas supplementing tryptophan largely restored these changes. This novel mechanism may be implicated in enhanced inflammatory responses to bacterial challenges following viral infection.
A Novel Dendritic Cell-Induced Model of Erosive Inflammatory Arthritis: Distinct Roles for Dendritic Cells in T Cell Activation and Induction of Local Inflammation
Authors: Leung Bernard P. , Conacher Margaret , Hunter David , McInnes Iain B. , Liew Foo Y. , Brewer James M. 
Published: April 2014

AbstractTransferring collagen-pulsed, bone marrow-derived dendritic cells (DCs) into congenic DBA/1 recipient mice produced arthritis in joints adjacent to the site of DC transfer and could be inhibited by treatment with TNF antagonists. Disease was Ag specific, as transfer of control, unpulsed DCs, or DCs pulsed with OVA did not produce arthritis. In contrast to other experimental arthritis models, DC-induced arthritis localized to the site of injection and did not spontaneously generalize to uninvolved joints, despite the demonstration of circulating collagen-reactive T cells. Similarly, transfer of T cells primed by collagen/DCs was not sufficient to produce arthritis in recipient mice. In collagen/DC-primed mice however, disease could be induced in uninvolved joints by local administration of noncollagen-pulsed DCs and this could be reduced through TNF inhibition. Similarly, injection of collagen/DC-primed mice with low-dose TNF also resulted in local induction of arthritis, as did administration of TNF to mice receiving T cells from collagen/DC but not OVA/DC-primed mice. Thus, we have demonstrated for the first time that administration of collagen-pulsed mature DCs is sufficient for the induction of arthritis. Furthermore, this disease process is mediated through both adaptive and innate effects of DCs; first, priming of autoreactive T cells and, second, induction of local inflammation via mediators such as TNF.