bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age-Related Dysregulation in CD8 T Cell Homeostasis: Kinetics of a Diversity Loss
Authors: LeMaoult Joël , Messaoudi Ilhem , Manavalan John S. , Potvin Heather , Nikolich-Z̆ugich Dragana , Dyall Ruben , Szabo Paul , Weksler Marc E. , Nikolich-Z̆ugich Janko 
Published: April 2014

AbstractRelative diversity and representation of peripheral T cells bearing different TCR Vβ families are remarkably tightly regulated between birth and advanced adulthood. By contrast, individual elderly humans and C3H.SW and B10.BR aged mice display drastic disruption in such regulation. It was suggested that the alterations in the murine aged T cell compartment were due to age-related clonal T cell expansions (TCE). Here, we studied the kinetics of homeostatic dysregulation of T cell populations in aged C57BL/6 (B6) mice. Using mAb staining, we show that the percentages of αβ+CD8+ or CD4+ T cells bearing different TCRVβ elements remain virtually constant in mice up to 12 mo of age. In 22-mo-old mice, however, there is a dramatic disturbance of this pattern owing to the emergence of CD8+ TCE. Expanded T cells did not show any obvious bias in Vβ usage and were derived in all cases examined thus far from a single clone. TCE appeared later in life, compared with B cell clonal expansions. However, and in contrast to those detected in humans, TCE were frequently unstable disappearing within 2–4 mo, with other TCE appearing within the same time frame. Additional studies carried on thymic T cells, thymectomized mice, and young T transferred cells into Rag1−/− mice suggest that the clonal expansions occur in the periphery and that their onset is accelerated by decreased thymic output and/or function(s).
Mycophenolate Mofetil Impairs the Maturation and Function of Murine Dendritic Cells
Authors: Mehling Annette , Grabbe Stephan , Voskort Maik , Schwarz Thomas , Luger Thomas A. , Beissert Stefan 
Published: April 2014

Abstract
The immunosuppressive drug, mycophenolate mofetil (MMF), has been successfully introduced in allogeneic transplantation medicine and, more recently, in the treatment of autoimmune skin disorders. MMF inhibits lymphocyte proliferation via a blockade of the enzyme inosine 5′-monophosphate dehydrogenase, an enzyme on which lymphocytes solely depend to generate the purines necessary for DNA/RNA synthesis. To investigate the effects of MMF on cutaneous immune responses, a murine model of contact hypersensitivity (CHS) was used, with oxazolone or trinitrochlorobenzene as a contact allergen. Compared with the respective vehicle, i.p. applied MMF significantly inhibited the elicitation and, surprisingly, the induction of CHS responses. This prompted further studies into the effects of MMF on Ag presentation. Bone marrow-derived dendritic cells (DC) were cultured with GM-CSF and IL-4 in the presence of MMF and were tested for their Ag-presenting capacity. Sensitization and elicitation of CHS and delayed-type hypersensitivity responses by s.c. injected haptenated DC were reduced upon preincubation of DC with MMF. CHS responses were not impaired upon resensitization, indicating that MMF does not induce hapten-specific immunotolerance. In addition, MMF decreased the ability of DC to stimulate allogeneic T cells in MLR assays. Accordingly, flow cytometric analyses revealed a dose-dependent reduction of the expression of CD40, CD80, CD86, I-A, and ICAM-1 on DC with a concurrent reduction of IL-12 production. These data suggest that MMF, in addition to affecting T lymphocytes, directly affects APC, resulting in an impairment of immune responses. They furthermore point to a possible role of inosine 5′-monophosphate dehydrogenase in the maturation of DC.
IL-3 Increases Production of B Lymphoid Progenitors from Human CD34+CD38− Cells
Authors: Crooks Gay M. , Hao Qian-Lin , Petersen Denise , Barsky Lora W. , Bockstoce David 
Published: April 2014

AbstractThe effect of IL-3 on the B lymphoid potential of human hemopoietic stem cells is controversial. Murine studies suggest that B cell differentiation from uncommitted progenitors is completely prevented after short-term exposure to IL-3. We studied B lymphopoiesis after IL-3 stimulation of uncommitted human CD34+CD38− cells, using the stromal cell line S17 to assay the B lymphoid potential of stimulated cells. In contrast to the murine studies, production of CD19+ B cells from human CD34+CD38− cells was significantly increased by a 3-day exposure to IL-3 (p &lt; 0.001). IL-3, however, did not increase B lymphopoiesis from more mature progenitors (CD34+CD38+ cells) or from committed CD34−CD19+ B cells. B cell production was increased whether CD34+CD38− cells were stimulated with IL-3 during cocultivation on S17 stroma, on fibronectin, or in suspension. IL-3Rα expression was studied in CD34+ populations by RT-PCR and FACS. High IL-3Rα protein expression was largely restricted to myeloid progenitors. CD34+CD38− cells had low to undetectable levels of IL-3Rα by FACS. IL-3-responsive B lymphopoiesis was specifically found in CD34+ cells with low or undetectable IL-3Rα protein expression. IL-3 acted directly on progenitor cells; single cell analysis showed that short-term exposure of CD34+CD38− cells to IL-3 increased the subsequent cloning efficiency of B lymphoid and B lymphomyeloid progenitors. We conclude that short-term exposure to IL-3 significantly increases human B cell production by inducing proliferation and/or maintaining the survival of primitive human progenitors with B lymphoid potential.
Antibody Production in Mice Deficient for Complement Receptors 1 and 2 Can Be Induced by IgG/Ag and IgE/Ag, But Not IgM/Ag Complexes
Authors: Applequist Steven E. , Dahlström Jörgen , Jiang Ning , Molina Hector , Heyman Birgitta 
Published: April 2014

AbstractDeficiencies in C factors C2, C3, or C4 as well as lack of C receptors 1 and 2 (CR1/2) lead to impaired Ab production. Classical pathway activation plays a major role, as mice deficient in factor B, a key factor in the alternative pathway, have normal Ab production. Abs in complex with their specific Ag are known to feedback regulate the Ab response, and enhanced responses are initiated by IgM, IgE, and IgG. IgM acts via the C system, whereas IgE and IgG can operate independently of C via Fc receptors. Here we have investigated whether these isotypes are able to enhance Ab responses in mice lacking CR1/2. SRBC-specific IgM, administered with SRBC, does not enhance Ab responses in these animals. In contrast, 2,4,6-trinitrophenyl-specific IgE and IgG2a, administered with BSA-2,4,6-trinitrophenyl, induce potent Ab responses in CR1/2-deficient mice. Additionally, BSA administered with CFA or alum induced strong Ab responses in the absence of CR1/2. These results indicate that CR1/2 is needed to promote IgM-mediated induction of primary Ab responses. The data also show that the need for CR1/2 can be circumvented by Abs typical of a secondary immune response forming complexes with Ag or by conventional adjuvants, presumably mimicking physiological inflammatory reactions.
Contemporary Analysis of MHC-Related Immunodominance Hierarchies in the CD8+ T Cell Response to Influenza A Viruses
Authors: Belz Gabrielle T. , Stevenson Philip G. , Doherty Peter C. 
Published: April 2014

AbstractEarly studies of influenza virus-specific CD8+ T cell-mediated immunity indicated that the level of CTL activity associated with H2Db is greatly diminished in mice that also express H2Kk. Such MHC-related immunodominance hierarchies are of some interest, as they could lead to variable outcomes for peptide-based vaccination protocols in human populations. The influence of H2Kk on the H2Db-restricted response profile has thus been looked at again using a contemporary, quantitative, IFN-γ-based flow cytometric assay. The depressive effect of H2Kk was very apparent for the influenza DbPA224 epitope and was also reproduced when CTL activity was measured for H2Db-expressing targets pulsed with the immunodominant NP366 peptide. The secondary CD8+IFN-γ+ DbNP366-specific response was much greater in parental H2b than in H2k×bF1 mice, but the sizes of the CD8+ sets specific for KkNP50 and DbNP366 were essentially equivalent in the F1 animals. Thus, although the immunodominance profile associated with DbNP366 is lost when H2Kk is also present, the response is still substantial. A further, MHC-related effect was also identified for the KkNS1152 epitope, which was consistently associated with a greater CD8+IFN-γ+ response in H2KkDb recombinant than in (H2KkDk × H2KbDb)F1 mice. The diminished DbPA224 response in H2k×bF1 mice was characterized by loss of a prominent Vβ7 TCR responder phenotype, supporting the idea that TCR deletion during ontogeny shapes the available repertoire. The overall conclusion is that these MHC-related immunodominance hierarchies are more subtle than the early CTL assays suggested and, although inherently unpredictable, are unlikely to cause a problem for peptide-based vaccine strategies.
An Essential Role for the IL-7 Receptor During Intrathymic Expansion of the Positively Selected Neonatal T Cell Repertoire
Authors: Hare Katherine J. , Jenkinson Eric J. , Anderson Graham 
Published: April 2014

AbstractIntrathymic T cell development is a multistage process involving discrete phases of proliferation as well as differentiation. From studies on IL-7 or IL-7Rα-deficient mice, it is clear that the IL-7 receptor (IL-7R) plays a critical role during the initial stages of intrathymic CD4−8− precursor development. In contrast, the role of IL-7R in later stages of thymocyte development are unclear. Here, we have used various approaches to investigate directly the role of the IL-7R in thymocyte positive selection and the recently described phase of postselection proliferation. First, we show that positive selection involves selective up-regulation of IL-7Rα- and IL-7Rγ-chains, with the majority of CD4+ and CD8+ cells being IL-7R+. Second, MHC class II+ thymic epithelium—which drives postselection proliferation—expresses IL-7 mRNA. Finally, analysis of positive selection and postselection proliferation in thymocytes from IL-7Rα−/− neonates shows that positive selection occurs normally, whereas postselection expansion is drastically reduced. Thus, our data provide the first evidence that, as well as playing a role during early phases of thymic development, IL-7R mediates intrathymic expansion of positively selected thymocytes, which may aid in establishment of the neonatal peripheral T cell pool.
T Cell Effector Function and Anergy Avoidance Are Quantitatively Linked to Cell Division
Authors: Wells Andrew D. , Walsh Matthew C. , Sankaran David , Turka Laurence A. 
Published: April 2014

AbstractWe have shown previously that T cells activated by optimal TCR and CD28 ligation exhibit marked proliferative heterogeneity, and ∼40% of these activated cells fail entirely to participate in clonal expansion. To address how prior cell division influences the subsequent function of primary T cells at the single cell level, primary CD4+ T cells were subjected to polyclonal stimulation, sorted based on the number of cell divisions they had undergone, and restimulated by ligation of TCR/CD28. We find that individual CD4+ T cells exhibit distinct secondary response patterns that depend upon their prior division history, such that cells that undergo more rounds of division show incrementally greater IL-2 production and proliferation in response to restimulation. CD4+ T cells that fail to divide after activation exist in a profoundly hyporesponsive state that is refractory to both TCR/CD28-mediated and IL-2R-mediated proliferative signals. We find that this anergic state is associated with defects in both TCR-coupled activation of the p42/44 mitogen-activated protein kinase (extracellular signal-related kinase 1/2) and IL-2-mediated down-regulation of the cell cycle inhibitor p27kip1. However, these defects are selective, as TCR-mediated intracellular calcium flux and IL-2R-coupled STAT5 activation remain intact in these cells. Therefore, the process of cell division or cell cycle progression plays an integral role in anergy avoidance in primary T cells, and may represent a driving force in the formation of the effector/memory T cell pool.
Selective Inhibition of IgG-Mediated Phagocytosis in Gelsolin-Deficient Murine Neutrophils
Authors: Serrander Lena , Skarman Petra , Rasmussen Birgitta , Witke Walter , Lew Daniel P. , Krause Karl-Heinz , Stendahl Olle , Nüße Oliver 
Published: April 2014

Abstract
Phagocytosis and the microbicidal functions of neutrophils require dynamic changes of the actin cytoskeleton. We have investigated the role of gelsolin, a calcium-dependent actin severing and capping protein, in peripheral blood neutrophils from gelsolin-null (Gsn−) mice. The phagocytosis of complement opsonized yeast was only minimally affected. In contrast, phagocytosis of IgG-opsonized yeast was reduced close to background level in Gsn− neutrophils. Thus, gelsolin is essential for efficient IgG- but not complement-mediated phagocytosis. Furthermore, attachment of IgG-opsonized yeast to Gsn− neutrophils was reduced (∼50%) but not to the same extent as ingestion (∼73%). This was not due to reduced surface expression of the Fcγ-receptor or its lateral mobility. This suggests that attachment and ingestion of IgG-opsonized yeast by murine neutrophils are actin-dependent and gelsolin is important for both steps in phagocytosis. We also investigated granule exocytosis and several steps in phagosome processing, namely the formation of actin around the phagosome, translocation of granules, and activation of the NADPH-oxidase. All these functions were normal in Gsn− neutrophils. Thus, the role of gelsolin is specific for IgG-mediated phagocytosis. Our data suggest that gelsolin is part of the molecular machinery that distinguishes complement and IgG-mediated phagocytosis. The latter requires a more dynamic reorganization of the cytoskeleton.
Selective Malformation of the Splenic White Pulp Border in L1-Deficient Mice
Authors: Wang Shih-Lien , Kutsche Michael , DiSciullo Gino , Schachner Melitta , Bogen Steven A. 
Published: April 2014

AbstractLymphocytes enter the splenic white pulp by crossing the poorly characterized boundary of the marginal sinus. In this study, we describe the importance of L1, an adhesion molecule of the Ig superfamily, for marginal sinus integrity. We find that germline insertional mutation of L1 is associated with a selective malformation of the splenic marginal sinus. Other splenic structures remain intact. Immunofluorescence analysis of the extracellular framework of the spleen, using an Ab to laminin, reveals that L1 knockout mice have an irregularly shaped, discontinuous white pulp margin. Electron microscopic analysis shows that it is associated with bizarrely shaped marginal sinus lining cells at the periphery of the white pulp. These abnormalities correlate with the localization of L1 in normal mice in that L1 is normally expressed on marginal sinus lining cells at the white pulp border. These L1-immunopositive lining cells coexpress high levels of mucosal addressin cell adhesion molecule-1 and vimentin, indicating that they are of fibroblastic lineage and express a well-characterized addressin. Our findings are the first to implicate L1 in splenic lymphoid architectural development. Moreover, these findings help define the poorly characterized sinusoidal boundary across which mononuclear cells cross to enter the splenic white pulp.
MHC Class II Transactivator Inhibits IL-4 Gene Transcription by Competing with NF-AT to Bind the Coactivator CREB Binding Protein (CBP)/p300
Authors: Sisk Tyler J. , Gourley Tania , Roys Stacey , Chang Cheong-Hee 
Published: April 2014

Abstract
The MHC class II transactivator (CIITA) activates the expression of multiple genes involved in Ag presentation, but inhibits Th2-type cytokine production, including IL-4, during Th1 cell differentiation. Th1 cells derived from CIITA-deficient mice produce both Th1- and Th2-type cytokines, and the introduction of CIITA to Th2 cells down-regulates Th2-type cytokine gene transcription. Here we show that the IL-4 promoter is regulated by multiple protein-protein interactions among CIITA, NF-AT, and coactivator CBP/p300. The introduction of CBP/p300 and NF-AT enhances the IL-4 promoter activity, and this activation was repressed by CIITA. Furthermore, our data show that CIITA competes with NF-AT to bind CBP/p300 and that this competition dramatically influences transcriptional activation of the IL-4 promoter. We identified two domains of CIITA that interact with two distinct domains of CBP/p300 that are also recognized by NF-AT. CIITA mutants that retain the ability to interact with CBP/p300 are sufficient to inhibit NF-AT-mediated IL-4 gene expression.
Identification and Functional Characterization of a New Gene Encoding the Mouse Terminal Complement Inhibitor CD59
Authors: Qian Yue-Ming , Qin Xuebin , Miwa Takashi , Sun Xiujun , Halperin Jose A. , Song Wen-Chao 
Published: April 2014

AbstractCD59 is a 18- to 20-kDa, GPI-anchored membrane protein that functions as a key regulator of the terminal step of the complement activation cascade. It restricts binding of C9 to the C5b-8 complex, thereby preventing the formation of the membrane attack complex (C5b-9 of complement). A single human CD59 gene has been identified, and corresponding genetic homologues from rat, mouse, and pig have been characterized in previous studies. In this study, we report the discovery and functional characterization of a separate cd59 gene in the mouse (referred to as cd59b, the previously characterized mouse cd59 gene as cd59a). Mouse cd59b is 85% and 63% identical to cd59a at the nucleotide and amino acid level, respectively. In cDNA transfection experiments with Chinese hamster ovary cells, peptide-tagged cd59b was detected on the cell surface by flow cytometry and was shown to be susceptible to phosphatidylinositol-specific phospholipase C cleavage. Chinese hamster ovary cells expressing cd59b were significantly more resistant than control cells to human and mouse complement-mediated lysis. These results suggest that cd59b encodes a GPI-anchored protein that is functionally active as a membrane attack complex inhibitor. Northern blot analysis revealed that cd59b is expressed selectively in the mouse testis. In contrast, the major transcript of cd59a was shown to be expressed at high levels in the heart, kidney, liver, and lung, but only minimally in the testis. These results revealed the existence of two distinct cd59 genes in the mouse that are differentially regulated and that may have nonoverlapping physiological functions in vivo.
The IgA/IgM Receptor Expressed on a Murine B Cell Lymphoma Is Poly-Ig Receptor
Authors: Phillips-Quagliata Julia M. , Patel Samir , Han Jing-Kang , Arakelov Sergei , Rao T. Dharma , Shulman Marc J. , Fazel Shafie , Corley Ronald B. , Everett Margaret , Klein Michel H. , Underdown Brian J. , Corthésy Blaise 
Published: April 2014

AbstractT560, a mouse B lymphoma that originated in gut-associated lymphoid tissue, expresses receptors that bind dimeric IgA and IgM in a mutually inhibitory manner but have little affinity for monomeric IgA. Evidence presented in this paper indicates that the receptor is poly-Ig receptor (pIgR) known in humans and domestic cattle to bind both IgA and IgM. The evidence includes the demonstration that binding of IgM is J chain dependent, and that pIg-precipitated receptor has an appropriate Mr of 116–120 kDa and can be detected on immunoblots with specific rabbit anti-mouse pIgR. Overlapping RT-PCR performed using template mRNA from T560 cells and oligonucleotide primer pairs designed from the published sequence of mouse liver pIgR indicate that T560 cells express mRNA virtually identical with that of the epithelial cell pIgR throughout its external, transmembrane, and intracytoplasmic coding regions. Studies using mutant IgAs suggest that the Cα2 domain of dimeric IgA is not involved in high-affinity binding to the T560 pIgR. Inasmuch as this mouse B cell pIgR binds IgM better than IgA, it is similar to human pIgR and differs from rat, mouse, and rabbit epithelial cell pIgRs that bind IgA but not IgM. Possible explanations for this difference are discussed. All clones of T560 contain some cells that spontaneously secrete both IgG2a and IgA, but all of the IgA recoverable from the medium and from cell lysates is monomeric; it cannot be converted to secretory IgA by T560 cells.
Efficient Internalization of IL-2 Depends on the Distal Portion of the Cytoplasmic Tail of the IL-2R Common γ-Chain and a Lymphoid Cell Environment
Authors: Yu Aixin , Olosz Ferenc , Choi Chris Y. , Malek Thomas R. 
Published: April 2014

Abstract
The common γ-chain (γc), a subunit of the IL-2R, is essential for high affinity ligand binding and signal transduction due to Jak3 association to γc. Another consequence of IL-2/IL-2R interaction is rapid receptor-mediated endocytosis of the receptor-ligand complex. In the present study, we establish that this rapid endocytosis of IL-2 in a T cell tumor line is dependent upon the cytoplasmic tail of γc. Deletion mutants of the cytoplasmic tail mapped this activity to 9 aa of γc, 45–54 aa distal to the transmembrane region. In contrast, ligand-independent constitutive endocytosis of γc occurred more slowly and was dependent upon a PEST sequence in a more membrane-proximal region of the cytoplasmic tail of γc. Thus, this receptor subunit may use distinct sorting signals for its constitutive regulation and ligand-induced endocytosis. Rapid endocytosis of IL-2 was inhibited by the tyrosine kinase inhibitor genistein, implicating a role for a signal transduction pathway in IL-2 internalization. However, one T cell line bearing a mutant γc exhibited impaired endocytosis of IL-2, despite normal IL-2-induced Jak/STAT activation. Furthermore, inefficient endocytosis of IL-2 was noted after transfection of the COS7 epithelial cell line with the IL-2R, and further reconstitution of these cells with Jak/STAT proteins did not enhance this internalization. Collectively, these latter findings indicate that rapid endocytosis of IL-2 is dependent upon cellular signaling in lymphoid cell environment that is not solely a consequence of the presence of the Jak/STAT pathway.
Effect of Integrin β2 Subunit Truncations on LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) Assembly, Surface Expression, and Function
Authors: Tan Suet-Mien , Hyland Robert H. , Al-Shamkhani Aymen , Douglass Wendy A. , Shaw Jacqueline M. , Law S. K. Alex 
Published: April 2014

AbstractLFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) are members of the β2 integrins involved in leukocyte function during immune and inflammatory responses. We aimed to determine a minimized β2 subunit that forms functional LFA-1 and Mac-1. Using a series of truncated β2 variants, we showed that the subregion Q23-D300 of the β2 subunit is sufficient to combine with the αL and αM subunits intracellularly. However, only the β2 variants terminating after Q444 promote cell surface expression of LFA-1 and Mac-1. Thus, the major cysteine-rich region and the three highly conserved cysteine residues at positions 445, 447, and 449 of the β2 subunit are not required for LFA-1 and Mac-1 surface expression. The surface-expressed LFA-1 variants are constitutively active with respect to ICAM-1 adhesion and these variants express the activation reporter epitope of the mAb 24. In contrast, surface-expressed Mac-1, both the wild type and variants, require 0.5 mM MnCl2 for adhesion to denatured BSA. These results suggest that the role of the β2 subunit in LFA-1- and Mac-1-mediated adhesion may be different.