bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzymatically Quiescent Heparanase Augments T Cell Interactions with VCAM-1 and Extracellular Matrix Components under Versatile Dynamic Contexts
Authors: Sotnikov Ilya , Hershkoviz Rami , Grabovsky Valentin , Ilan Neta , Cahalon Liora , Vlodavsky Israel , Alon Ronen , Lider Ofer
Published: April 2014

During their migration into inflammatory sites, immune cells, such as T cells, secrete extracellular matrix (ECM)-degrading enzymes, such as heparanase, which, under mildly acidic conditions, degrade heparan sulfate proteoglycans (HSPG). We have previously shown that at pH 7.2, human placental heparanase loses its enzymatic activity, while retaining its ability to bind HSPG and promote T cell adhesion to unfractionated ECM. We now demonstrate that the 65-kDa recombinant human heparanase, which is devoid of enzymatic activity, but can still bind HSPG, captures T cells under shear flow conditions and mediates their rolling and arrest, in the absence or presence of stromal cell-derived factor 1α (SDF-1α; CXCL12), in an α4β1-VCAM-1-dependent manner. Furthermore, heparanase binds to and induces T cell adhesion to key ECM components, like fibronectin and hyaluronic acid, in β1 integrin- and CD44-specific manners, respectively, via the activation of the protein kinase C and phosphatidylinositol 3-kinase intracellular signaling machineries. Although the nature of the putative T cell heparanase-binding moiety is unknown, it appears that heparanase exerts its proadhesive activity by interacting with the T cells’ surface HSPG, because pretreatment of the cells with heparinase abolished their subsequent response to heparanase. Also, heparanase augmented the SDF-1α-triggered phosphorylation of Pyk-2 and extracellular signal-regulated kinase-2 implicated in integrin functioning. Moreover, heparanase, which had no chemotactic effect on T cells on its own, augmented the SDF-1α-induced T cell chemotaxis across fibronectin. These findings add another dimension to the known versatility of heparanase as a key regulator of T cell activities during inflammation, both in the context of the vasculature and at extravascular sites.
Platelets, after Exposure to a High Shear Stress, Induce IL-10-Producing, Mature Dendritic Cells In Vitro
Authors: Hagihara Masao , Higuchi Ayako , Tamura Noriko , Ueda Yoko , Hirabayashi Kaori , Ikeda Yasuo , Kato Shunichi , Sakamoto Shinji , Hotta Tomomitsu , Handa Shunnosuke , Goto Shinya
Published: April 2014

There is evidence for immune system involvement in atherogenesis. In the present study the effect of platelets on dendritic cells (DC), an important immunologic regulator, was examined in vitro. Platelet-rich plasma, after exposure to shear stress, was added to human monocyte-derived immature DC, which were then examined for surface Ag expression, allogeneic T lymphocyte stimulatory activity, and cytokine production. After exposure, the number of anti-CD40 ligand (anti-CD40L) and anti-P-selectin IgG molecules bound per platelet was increased. These activated platelets induced DC maturation, as revealed by significant up-regulation of CD83, CD80, and CD86 Ags. The addition of platelets in the presence of IFN-γ plus LPS significantly enhanced IL-10 production from immature DC. After platelet addition, mature DC provoked a significant proliferation of allogeneic naive T lymphocytes. These activated T cells showed lower IFN-γ production than those stimulated by LPS- and IFN-γ-treated DC. CD40L on the platelet surface was not involved in maturation of DC, as mAb to CD40L failed to block maturation. The effect of platelets was observed even if platelets and DC were separated using large pore-sized membranes or when platelets were depleted from plasma by centrifugation. Furthermore, it was abrogated after the depletion of protein fraction. Thus, soluble protein factors excreted from activated platelets contribute to IL-10-producing DC maturation.
κ Editing Rescues Autoreactive B Cells Destined for Deletion in Mice Transgenic for a Dual Specific Anti-Laminin Ig
Authors: Brady Graham F. , Congdon Kendra L. , Clark Amy G. , Sackey Faustina N. A. , Rudolph Earl H. , Radic Marko Z. , Foster Mary H.
Published: April 2014

We explored mechanisms involved in B cell self-tolerance in a double- and triple-transgenic mouse model bearing the LamH-Cμ Ig H chain conventional transgene and a gene-targeted replacement for a functional Vκ8Jκ5 L chain gene. Whereas the H chain is known to generate anti-laminin Ig in combination with multiple L chains, the H + L Ig binds ssDNA in addition to laminin. Immune phenotyping indicates that H + L transgenic B cells are regulated by clonal deletion, receptor editing via secondary rearrangements at the nontargeted κ allele, and anergy. Collectively, the data suggest that multiple receptor-tolerogen interactions regulate autoreactive cells in the H + L double-transgenic mice. Generation of H + LL triple-transgenic mice homozygous for the targeted L chain to exclude secondary κ rearrangements resulted in profound B cell depletion with absence of mature B cells in the bone marrow. We propose that the primary tolerogen of dual reactive B cells in this model is not ssDNA, but a strongly cross-linking tolerogen, presumably basement membrane laminin, that triggers recombination-activating gene activity, L chain editing, and deletion.
Autoreactive T Cells Persist in Rats Protected against Experimental Autoimmune Encephalomyelitis and Can Be Activated through Stimulation of Innate Immunity
Authors: Conant Stephanie B. , Swanborg Robert H.
Published: April 2014

Lewis rats can be rendered unresponsive to experimental autoimmune encephalomyelitis by immunization with myelin basic protein (MBP), or MBP68–86, the dominant encephalitogenic MBP epitope for this strain, administered in IFA. However, protected rats harbor potentially encephalitogenic T cells, which are maintained in an inactive state. We investigated whether these quiescent effector cells could be activated in vitro. Although these T cells respond poorly to MBP68–86, they proliferate vigorously whether cocultured with MBP68–86 and either IL-2 or IL-12, suggesting that the T cells are in a state of anergy. Moreover, we could activate these anergic T cells with peptide and cytosine-guanine dinucleotide (CpG) oligonucleotide, but not control oligonucleotide, suggesting that products of the innate immune response are capable of activating anergic autoreactive T cells. The activated T cells produced the proinflammatory cytokine, IFN-γ in response to IL-12, and IL-6 was secreted in response to CpG oligonucleotide. IL-6 has been reported to play a role in T cell activation by blocking T regulatory/suppressor (Treg) cell-mediated suppression through a Toll-like receptor-dependent pathway. However, anti-IL-6 mAb did not block CpG activation of the anergized cells. In contrast, anti-TGF-β1 Ab released the unresponsive T cells from the anergic state in the presence of MBP68–86, whereas TGF-β1 inhibited proliferation of MBP68–86- plus CpG-activated T cells. Because TGF-β1 has previously been implicated in Treg activity, this finding is consistent with a role for Treg cells in maintaining autoreactive T cells in the anergic state.
Role of Cross-Talk between IFN-α-Induced Monocyte-Derived Dendritic Cells and NK Cells in Priming CD8+ T Cell Responses against Human Tumor Antigens
Authors: Tosi Diego , Valenti Roberta , Cova Agata , Sovena Gloria , Huber Veronica , Pilla Lorenzo , Arienti Flavio , Belardelli Filippo , Parmiani Giorgio , Rivoltini Licia
Published: April 2014

In the present study we evaluated the role of IFN-α in the generation of dendritic cells (IFN-DCs) with priming activity on CD8+ T lymphocytes directed against human tumor Ags. A 3-day treatment of monocytes, obtained as adherent PBMCs from HLA-A*0201+ healthy donors, with IFN-α and GM-CSF led to the differentiation of DCs displaying a semimature phenotype, but promptly inducing CD8+ T cell responses after one in vitro sensitization with peptides derived from melanoma (gp100209–217 and MART-1/Melan-A27–35) and adenocarcinoma (CEA605–613) Ags. However, these features were lost when IFN-DCs were generated from immunosorted CD14+ monocytes. The ability of adherent PBMCs to differentiate into IFN-DCs expressing higher levels of costimulatory molecules and exerting efficient T cell priming capacity was associated with the presence of contaminating NK cells, which underwent phenotypic and functional activation upon IFN-α treatment. NK cell boost appeared to be mediated by both direct and indirect (i.e., mediated by IFN-DCs) mechanisms. Experiments performed to prove the role of contaminating NK cells in DC differentiation showed that IFN-DCs generated in the absence of NK were phenotypically less mature and could not efficiently prime antitumor CD8+ lymphocytes. Reciprocally, IFN-DCs raised from immunosorted CD14+ monocytes regained their T cell priming activity when NK cells were added to the culture before IFN-α and GM-CSF treatment. Together, our data suggest that the ability of IFN-DCs to efficiently prime anti-tumor CD8+ T lymphocytes relied mostly on the positive cross-talk occurring between DCs and NK cells upon stimulation with IFN-α.
Human T Cell Activation by Costimulatory Signal-Deficient Allogeneic Cells Induces Inducible Costimulator-Expressing Anergic T Cells with Regulatory Cell Activity
Authors: Vermeiren Jan , Ceuppens Jan L. , Van Ghelue Marijke , Witters Peter , Bullens Dominique , Mages Hans Werner , Kroczek Richard A. , Van Gool Stefaan W.
Published: April 2014

Although immunoregulation by several types of regulatory T cells is now clearly established in mice, the demonstration of such regulatory T cells in humans has been proven more difficult. In this study we demonstrate the induction of anergic regulatory T cells during an MLR performed in the presence of blocking mAb to the costimulatory molecules CD40, CD80, and CD86. Despite this costimulation blockade, which totally blocks T cell proliferation and cytokine production, a nonproliferating T cell subpopulation was activated to express inducible costimulator (ICOS). These ICOS+ cells were anergic when restimulated with unmanipulated allogeneic stimulator cells at the level of proliferation and Th1 and Th2 cytokine production, but they did produce IL-10. These ICOS-expressing cells also blocked the capacity of reciprocal ICOS-negative cells to proliferate and to produce cytokines. ICOS+ anergic cells could suppress allogenic responses of either primed or naive T cells through inhibition of IL-2 gene transcription. Suppression was not mediated by IL-10 and did not require ICOS-ICOS ligand interaction, but depended on cell-cell contact. Thus, a subtype of regulatory T cells in human blood can be activated in the absence of costimulatory signals from CD40, CD80, and CD86, and they can be identified by expression of ICOS after activation.
Dendritic Cells Exposed to Herpes Simplex Virus In Vivo Do Not Produce IFN-α after Rechallenge with Virus In Vitro and Exhibit Decreased T Cell Alloreactivity
Authors: Björck Pia
Published: April 2014

Plasmacytoid dendritic cells (DC) are known to produce large amounts of IFN-α when stimulated with virus in vivo and in vitro. Immunohistological staining of spleens from mice taken at different times after HSV infection revealed an early infiltration of plasmacytoid DC whereas both the myeloid DC and lymphoid-related DC had different kinetics. Upon rechallenge with virus in vitro, total splenic DCs from viral-infected mice were unable to produce IFN-α when compared with DC from mice that received an initial in vivo injection with PBS. Furthermore, DC from mice that were infected with increasing doses of HSV expressed high levels of accessory and activation molecules compared with control mice. However, when cultured in vitro together with allogeneic T cells, DC from mice that had been exposed to the highest viral titers in vivo induced the lowest levels of T cell proliferation. DC exposed to PBS in vivo promoted a Th1 response upon coculture with CD4+ T cells whereas T cells cultured with DC exposed to increasing viral titers in vivo resulted in a gradually decreased Th1 response. The data suggest HSV induces DC maturation and at higher titers, exhaustion, diminishing T cell proliferation, and IFN-γ secretion.
Nonmyeloablative Bone Marrow Transplantation of BXSB Lupus Mice Using Fully Matched Allogeneic Donor Cells from Green Fluorescent Protein Transgenic Mice
Authors: Jones Olcay Y. , Steele Ann , Jones Joe M. , Marikar Yasmin , Chang Yenhui , Feliz Alexander , Cahill Richard A. , Good Robert A.
Published: April 2014

Male BXSB mice, a mouse model of systemic lupus erythematosus, were given bone marrow transplants (BMT) at 20 wk of age using MHC-matched donor cells and nonmyeloablative conditioning (550 cGy irradiation). Transplanted mice and irradiation controls were followed for a period of 20 wk. Mice transgenic for green fluorescent protein were used as donors to allow tracking of donor cells and a determination of chimerism. Radiation controls had reduced renal pathology at 10 wk posttransplant, but not at 20 wk compared with untreated mice, while nonmyeloablative BMT mice had significantly reduced pathology at both time intervals. The monocytosis characteristic of older BXSB mice was also reduced by BMT, but the treatment did not prevent production of Ab to dsDNA. A stable chimerism of 24–40% donor CD45-positive cells was achieved in spleen and bone marrow, and there was no evidence of clinical graft vs host disease. Donor cells were detected in most recipient organs, notably the thymus and renal glomeruli. The results suggest that complete depletion of mature lymphocytes or of progenitor stem cells is not required to control lupus nephritis in BXSB mice.
Helper Requirements for Generation of Effector CTL to Islet β Cell Antigens
Authors: Behrens Georg M. N. , Li Ming , Davey Gayle M. , Allison Janette , Flavell Richard A. , Carbone Francis R. , Heath William R.
Published: April 2014

We have dissected the helper requirements for converting a tolerogenic CD8 T cell response into one capable of causing destruction of the pancreatic islets. Injection of naive OVA-specific CD8 T cells into transgenic mice expressing OVA in the pancreas only resulted in islet destruction when activated CD4 Th cells were coinjected. This requirement for activated CD4 T cell help for induction of primary CD8 T cell-mediated immunity to tissue Ags contrasts recent reports suggesting that help is only important for CTL memory. Our findings show that signaling of CD40 on the dendritic cell presenting to CD8 T cells is important, but not sufficient, for induction of diabetes. Furthermore, once helpers are activated, they need not recognize Ag on the dendritic cells they license. This provides insight into the helper requirements for adoptive transfer immunotherapy of tumors and suggests key points for inhibition of CTL-mediated autoimmunity.
A Proline-Rich Motif in the C Terminus of Akt Contributes to Its Localization in the Immunological Synapse
Authors: Kane Lawrence P. , Mollenauer Marianne N. , Weiss Arthur
Published: April 2014

The serine/threonine kinases of the Akt/protein kinase B family are regulated in part by recruitment to the plasma membrane, which is accomplished by the binding of an N-terminal PH domain to the phosphatidylinositol 3-kinase products phosphoinositol 3,4,5-trisphosphate and phosphoinositol 3,4-bisphosphate. We have examined Akt localization in a murine T cell clone (D10) before and after stimulation by APC/Ag, and we found that whereas the pleckstrin homology domain is required for plasma membrane recruitment of Akt upon T cell activation, the C terminus of the kinase restricts its cellular localization to the immunologic synapse formed at the site of T cell/APC contact. A recently described proline-rich motif in this region appears to be important for proper localization of full-length Akt. Moreover, a form of Akt in which this motif was mutated acts as a potent dominant negative construct to block T cell activation. Therefore, multiple mechanisms are involved in the proper targeting of Akt during the early events of T cell activation.
Lymphocyte Activation Gene-3 (CD223) Regulates the Size of the Expanding T Cell Population Following Antigen Activation In Vivo
Authors: Workman Creg J. , Cauley Linda S. , Kim In-Jeong , Blackman Marcia A. , Woodland David L. , Vignali Dario A. A.
Published: April 2014

Lymphocyte activation gene-3 (LAG-3) is a CD4-related, activation-induced cell surface molecule that binds to MHC class II with high affinity. In this study, we used four experimental systems to reevaluate previous suggestions that LAG-3−/− mice had no T cell defect. First, LAG-3−/− T cells exhibited a delay in cell cycle arrest following in vivo stimulation with the superantigen staphylococcal enterotoxin B resulting in increased T cell expansion and splenomegaly. Second, increased T cell expansion was also observed in adoptive recipients of LAG-3−/− OT-II TCR transgenic T cells following in vivo Ag stimulation. Third, infection of LAG-3−/− mice with Sendai virus resulted in increased numbers of memory CD4+ and CD8+ T cells. Fourth, CD4+ T cells exhibited a delayed expansion in LAG-3−/− mice infected with murine gammaherpesvirus. In summary, these data suggest that LAG-3 negatively regulates T cell expansion and controls the size of the memory T cell pool.
IL-4 Protects Tumor Cells from Anti-CD95 and Chemotherapeutic Agents via Up-Regulation of Antiapoptotic Proteins
Authors: Conticello Concetta , Pedini Francesca , Zeuner Ann , Patti Mariella , Zerilli Monica , Stassi Giorgio , Messina Angelo , Peschle Cesare , De Maria Ruggero
Published: April 2014

We recently proposed that Th1 and Th2 cytokines exert opposite effects on the pathogenesis and clinical outcome of organ-specific autoimmunity by altering the expression of genes involved in target cell survival. Because a Th2 response against tumors is associated with poor prognosis, we investigated the ability of IL-4 to protect tumor cells from death receptor- and chemotherapy-induced apoptosis. We found that IL-4 treatment significantly reduced CD95 (Fas/APO-1)- and chemotherapeutic drug-induced apoptosis in prostate, breast, and bladder tumor cell lines. Analysis of antiapoptotic protein expression revealed that IL-4 stimulation resulted in up-regulation of cellular (c) FLIP/FLAME-1 and Bcl-xL. Exogenous expression of cFLIP/FLAME-1 inhibited apoptosis induced by CD95 and to a lesser extent by chemotherapy, while tumor cells transduced with Bcl-xL were substantially protected both from CD95 and chemotherapeutic drug stimulation. Moreover, consistent IL-4 production and high expression of both cFLIP/FLAME-1 and Bcl-xL were observed in primary prostate, breast, and bladder cancer in vivo. Finally, primary breast cancer cells acquired sensitivity to apoptosis in vitro only in the absence of IL-4. Thus, IL-4 protects tumor cells from CD95- and chemotherapy-induced apoptosis through the up-regulation of antiapoptotic proteins such as cFLIP/FLAME-1 and Bcl-xL. These findings may provide useful information for the development of therapeutic strategies aimed at restoring the functionality of apoptotic pathways in tumor cells.
Mutational Analysis of Terminal Deoxynucleotidyltransferase- Mediated N-Nucleotide Addition in V(D)J Recombination
Authors: Repasky Jamie A. E. , Corbett Elizabeth , Boboila Cristian , Schatz David G.
Published: April 2014

The addition of nontemplated (N) nucleotides to coding ends in V(D)J recombination is the result of the action of a unique DNA polymerase, TdT. Although N-nucleotide addition by TdT plays a critical role in the generation of a diverse repertoire of Ag receptor genes, the mechanism by which TdT acts remains unclear. We conducted a structure-function analysis of the murine TdT protein to determine the roles of individual structural motifs that have been implicated in protein-protein and protein-DNA interactions important for TdT function in vivo. This analysis demonstrates that the N-terminal portion of TdT, including the BRCA-1 C-terminal (BRCT) domain, is not required for TdT activity, although the BRCT domain clearly contributes quantitatively to N-nucleotide addition activity. The second helix-hairpin-helix domain of TdT, but not the first, is required for activity. Deletional analysis also suggested that the entire C-terminal region of TdT is necessary for N-nucleotide addition in vivo. The long isoform of TdT was found to reduce N-nucleotide addition by the short form of TdT, but did not increase nucleotide deletion from coding ends in either human or rodent nonlymphoid cells. We consider these results in light of the recently reported structure of the catalytic region of TdT.
V Region Carbohydrate and Antibody Expression
Authors: Gala Françoise A. , Morrison Sherie L.
Published: April 2014

N-Linked carbohydrates are frequently found in the V region of Ig H chains and can have a positive or negative effect on Ag binding affinity. We have studied a murine anti-α(1→6) dextran VH that contains a carbohydrate in complementarity-determining region 2 (CDR2). This carbohydrate remains high mannose rather than being processed to a complex form, as would be expected for glycans on exposed protein loops. We have shown that the glycan remained high mannose when murine-human chimeric Abs were produced in a variety of cell types. Also, when another carbohydrate was present in CDR1, CDR2, or CDR3 of the L chain, the VH CDR2 glycan remained high mannose. Importantly, we found that when the anti-dextran VH CDR2 replaced CDR2 of an anti-dansyl VH, the glycosylation site was used, but H chains were withheld in the endoplasmic reticulum and did not traffic to the Golgi apparatus. These results suggest that inappropriate V region glycosylation could contribute to ineffective Ab production from expressed Ig genes. In some cases, a carbohydrate addition sequence generated by either V region rearrangement or somatic hypermutation may result in an Ab that cannot be properly folded and secreted.
Cathepsin G, and Not the Asparagine-Specific Endoprotease, Controls the Processing of Myelin Basic Protein in Lysosomes from Human B Lymphocytes
Authors: Burster Timo , Beck Alexander , Tolosa Eva , Marin-Esteban Viviana , Rötzschke Olaf , Falk Kirsten , Lautwein Alfred , Reich Michael , Brandenburg Jens , Schwarz Gerold , Wiendl Heinz , Melms Arthur , Lehmann Rainer , Stevanovic Stefan , Kalbacher Hubert , Driessen Christoph
Published: April 2014

The asparagine-specific endoprotease (AEP) controls lysosomal processing of the potential autoantigen myelin basic protein (MBP) by human B lymphoblastoid cells, a feature implicated in the immunopathogenesis of multiple sclerosis. In this study, we demonstrate that freshly isolated human B lymphocytes lack significant AEP activity and that cleavage by AEP is dispensable for proteolytic processing of MBP in this type of cell. Instead, cathepsin (Cat) G, a serine protease that is not endogenously synthesized by B lymphocytes, is internalized from the plasma membrane and present in lysosomes from human B cells where it represents a major functional constituent of the proteolytic machinery. CatG initialized and dominated the destruction of intact MBP by B cell-derived lysosomal extracts, degrading the immunodominant MBP epitope and eliminating both its binding to MHC class II and a MBP-specific T cell response. Degradation of intact MBP by CatG was not restricted to a lysosomal environment, but was also performed by soluble CatG. Thus, the abundant protease CatG might participate in eliminating the immunodominant determinant of MBP. Internalization of exogenous CatG represents a novel mechanism of professional APC to acquire functionally dominant proteolytic activity that complements the panel of endogenous lysosomal enzymes.
Cathepsin E: A Novel Target for Regulation by Class II Transactivator
Authors: Yee Christina S. K. , Yao Yongxue , Li Ping , Klemsz Michael J. , Blum Janice S. , Chang Cheong-Hee
Published: April 2014

The aspartic proteinase cathepsin E (CatE) has been implicated in Ag processing. In this study we report that CatE expression is negatively regulated by the MHC class II transactivator (CIITA). CIITA-deficient murine and human B cells expressed greater CatE than wild-type B cells, whereas overexpression of CIITA in a human gastric carcinoma cell line, AGS, resulted in decreased CatE mRNA and protein. AGS cells expressing CIITA also exhibited decreased processing of OVA Ag. Inhibition of CatE expression is specific to the type III CIITA isoform and maps to the acidic and proline/serine/threonine-rich (PST) protein domains of CIITA. We found that CatE expression is inducible by PU.1 and p300, and that this induction can be reversed by CIITA. These findings demonstrate a novel phenomenon: regulation of CatE Ag processing by CIITA in an isoform-dependent manner.
Initial Stages of Mammary Tumor Virus Infection Are Superantigen Independent
Authors: Pobezinskaya Yelena , Chervonsky Alexander V. , Golovkina Tatyana V.
Published: April 2014

Exogenous mouse mammary tumor virus (MMTV) is transmitted via the milk from infected mothers to newborn pups. Efficient MMTV transmission is dependent on proliferation of T cells with particular TCR β-chains, which occurs upon recognition of virally encoded superantigen (SAg) bound to MHC class II molecules. It is assumed that infection of these dividing cells favors MMTV amplification. SAg is important for MMTV infection, as mice that lack SAg-cognate T cells due to expression of endogenous Mtv loci or mice that express inappropriate MHC haplotypes unable to present viral SAg efficiently were shown to be resistant to MMTV infection. However, this resistance was not absolute, as these mice developed late onset MMTV-induced mammary tumors. In this study, we show that the success of initial MMTV infection in neonates is independent of SAg function but depends on the developmentally regulated proliferation of target cells. However, SAg was absolutely required for virus spread following completion of this proliferative stage.
Immune-Deficient Drosophila melanogaster: A Model for the Innate Immune Response to Human Fungal Pathogens
Authors: Alarco Anne-Marie , Marcil Anne , Chen Jian , Suter Beat , Thomas David , Whiteway Malcolm
Published: April 2014

We explored the host-pathogen interactions of the human opportunistic fungus Candida albicans using Drosophila melanogaster. We established that a Drosophila strain devoid of functional Toll receptor is highly susceptible to the human pathogen C. albicans. Using this sensitive strain, we have been able to show that a set of specific C. albicans mutants of different virulence in mammalian infection models are also impaired in virulence in Drosophila and remarkably display the same rank order of virulence. This immunodeficient insect model also revealed virulence properties undetected in an immunocompetent murine model of infection. The genetic systems available in both host and pathogen will enable the identification of host-specific components and C. albicans genes involved in the host-fungal interplay.
Specific Recognition of the Viral Protein UL18 by CD85j/LIR-1/ILT2 on CD8+ T Cells Mediates the Non-MHC-Restricted Lysis of Human Cytomegalovirus-Infected Cells
Authors: Saverino Daniele , Ghiotto Fabio , Merlo Andrea , Bruno Silvia , Battini Lorenzo , Occhino Marzia , Maffei Massimo , Tenca Claudya , Pileri Stefano , Baldi Lucia , Fabbi Marina , Bachi Angela , De Santanna Amleto , Grossi Carlo E. , Ciccone Ermanno
Published: April 2014

Immune evasion mechanisms of human CMV are known; however, the immune control of infection remains poorly elucidated. We show that interaction between the viral protein UL18 on infected cells and the invariant receptor CD85j/LIR-1/ILT2 expressed on CTL is relevant for the control of infection. Resting and activated CD8+ T cells lysed UL18 expressing cells, whereas cells infected with CMV defective for UL18 were not killed. Lysis was not dependent on CD8+ T cell Ag specificity, MHC-unrestricted and specifically blocked by anti-CD85j and anti-UL18 mAb. Moreover, soluble recombinant UL18Fc immunoprecipitated CD85j from T cells. Activation is mediated by CD85j and its pathway is unrelated to CD3/TCR engagement. UL18 is detected in immunocompromised patients with productive infection and the mechanism used in vivo by human CMV to ensure survival of the immunocompetent host may be mediated by activation signals delivered by infected cells to T lymphocytes via UL18/CD85j interactions.
Monosodium Urate Crystals Synergize with IFN-γ to Generate Macrophage Nitric Oxide: Involvement of Extracellular Signal-Regulated Kinase 1/2 and NF-κB
Authors: Jaramillo Maritza , Naccache Paul H. , Olivier Martin
Published: April 2014

Elevated NO production has been detected in patients suffering from various arthropathies; however, its role and regulation during gouty arthritis remain largely unexplored. Monosodium urate (MSU) crystals, the causative agent of gout, have been shown to induce NO generation in vivo and inducible NO synthase (iNOS) expression in human monocytes. The present study was designed to evaluate the ability of MSU crystals to modulate macrophage (Mφ) iNOS expression and NO synthesis and to investigate the molecular mechanisms underlying these cellular responses. We found that MSU crystals did not induce NO production in murine J774 Mφ. However, a synergistic effect on the level of iNOS expression and NO generation was observed in cells exposed to MSU crystals in combination with IFN-γ. Characterization of the second messengers involved revealed the requirement of IFN-γ-mediated Janus kinase 2/STAT1α activation even though MSU crystals did not modulate this signaling cascade by themselves. MSU crystals exerted their up-regulating effect by increasing extracellular signal-regulated kinase (ERK) 1/2 phosphorylation and NF-κB nuclear translocation in response to IFN-γ. The use of specific inhibitors against either NF-κB or the ERK1/2 pathway significantly reduced MSU + IFN-γ-inducible NF-κB activity, iNOS expression, and NO production. Altogether, these data indicate that MSU crystals exert a potent synergistic effect on the IFN-γ-inducible Mφ NO generation via ERK1/2- and NF-κB-dependent pathways. Understanding the molecular mechanisms through which MSU crystals amplify Mφ responses to proinflammatory cytokines such as IFN-γ will contribute to better define their role in NO regulation during gout, in particular, and inflammation, in general.
Metastable Tolerance to Rhesus Monkey Renal Transplants Is Correlated with Allograft TGF-β1+CD4+ T Regulatory Cell Infiltrates
Authors: Torrealba Jose R. , Katayama Masaaki , Fechner John H. , Jankowska-Gan Ewa , Kusaka Satoshi , Xu Qingyong , Schultz Jacqueline M. , Oberley Terry D. , Hu Huaizhong , Hamawy Majed M. , Jonker Margreet , Wubben Jacqueline , Doxiadis Gaby , Bontrop Ronald , Burlingham William J. , Knechtle Stuart J.
Published: April 2014

Approaches that prevent acute rejection of renal transplants in a rhesus monkey model were studied to determine a common mechanism of acceptance. After withdrawal of immunosuppression, all 14 monkeys retained normal allograft function for >6 mo. Of these, nine rejected their renal allograft during the study, and five maintained normal function throughout the study period. The appearance of TGF-β1+ interstitial mononuclear cells in the graft coincided with a nonrejection histology, whereas the absence/disappearance of these cells was observed with the onset of rejection. Analysis with a variety of TGF-β1-reactive Abs indicated that the tolerance-associated infiltrates expressed the large latent complex form of TGF-β1. Peripheral leukocytes from rejecting monkeys lacking TGF-β1+ allograft infiltrates responded strongly to donor Ags in delayed-type hypersensitivity trans-vivo assays. In contrast, allograft acceptors with TGF-β1+ infiltrates demonstrated a much weaker peripheral delayed-type hypersensitivity response to donor alloantigens (p < 0.01 vs rejectors), which could be restored by Abs that either neutralized active TGF-β1 or blocked its conversion from latent to active form. Anti-IL-10 Abs had no restorative effect. Accepted allografts had CD8+ and CD4+ interstitial T cell infiltrates, but only the CD4+ subset included cells costaining for TGF-β1. Our data support the hypothesis that the recruitment of CD4+ T regulatory cells to the allograft interstitium is a final common pathway for metastable renal transplant tolerance in a non-human primate model.
Identification of Anti-Plasmin Antibodies in the Antiphospholipid Syndrome That Inhibit Degradation of Fibrin
Authors: Yang Cheng-De , Hwang Kwan-Ki , Yan Weihong , Gallagher Kerry , FitzGerald John , Grossman Jennifer M. , Hahn Bevra H. , Chen Pojen P.
Published: April 2014

The combined presence of anti-phospholipid Ab (aPL) and thrombosis is recognized as the antiphospholipid syndrome (APS). The aPL represent a heterogeneous group of Ab that recognize various phospholipids (PL), PL-binding plasma proteins, and/or PL-protein complexes. Recently, we found the presence of antithrombin Ab in some APS patients and that some of these anti-thrombin Ab could inhibit thrombin inactivation by antithrombin. Considering that thrombin is homologous to plasmin, which dissolves fibrin, we hypothesize that some APS patients may have Ab that react with plasmin, and that some anti-plasmin Ab may interfere with the plasmin-mediated lysis of fibrin clots. To test this hypothesis, we searched for anti-plasmin Ab in APS patients and then studied those found for their effects on the fibrinolytic pathway. The results revealed that seven of 25 (28%) APS patients have IgG anti-plasmin Ab (using the mean OD plus 3 SD of 20 normal controls as the cutoff) and that six of six patient-derived IgG anti–thrombin mAb bind to plasmin with relative Kd values ranging from 5.6 × 10−8 to 1 × 10−6 M. These Kd values probably represent affinities in the higher ranges known for human IgG autoantibodies against protein autoantigens. Of these mAb, one could reduce the plasmin-mediated lysis of fibrin clots. These findings suggest that plasmin may be an important driving Ag for some aPL B cells in APS patients, and that the induced anti-plasmin Ab may act either directly, by binding to plasmin and inhibiting its fibrinolytic activity, or indirectly, by cross-reacting with other homologous proteins in the coagulation cascade to promote thrombosis.
An IL-12-Independent Role for CD40-CD154 in Mediating Effector Responses: Studies in Cell-Mediated Glomerulonephritis and Dermal Delayed-Type Hypersensitivity
Authors: Ruth Amanda-Jane , Kitching A. Richard , Li Ming , Semple Timothy J. , Timoshanko Jennifer R. , Tipping Peter G. , Holdsworth Stephen R.
Published: April 2014

Crescentic glomerulonephritis (GN) results from IL-12-driven Th1-directed cell-mediated responses (akin to delayed-type hypersensitivity (DTH)) directed against glomerular Ags. CD40-CD154 interactions are critical for IL-12 production and Th1 polarization of immune responses. Crescentic anti-glomerular basement membrane GN was induced in C57BL/6 (wild-type (WT)) mice (sensitized to sheep globulin) by planting this Ag (as sheep anti-mouse glomerular basement membrane globulin) in their glomeruli. Crescentic GN did not develop in CD40−/− mice due to significantly reduced nephritogenic Th1 responses. IL-12 was administered to CD40−/− mice with GN to dissect interactions between IL-12 and CD40 in inducing nephritogenic immunity and injury. Administration of IL-12 to CD40−/− mice restored Th cell IFN-γ production, and up-regulated intrarenal chemokines and glomerular T cell and macrophage accumulation compared with WT control mice. Despite this, renal macrophages were not activated and renal injury and dermal DTH were not restored. Thus, CD40-directed IL-12 drives Th1 generation and effector cell recruitment but CD40 is required for activation. To test this hypothesis, activated OT-II OVA-specific CD4+ cells and OVA323–339-loaded nonresponsive APCs were transferred into footpads of WT, CD40−/−, and macrophage-depleted WT mice. WT mice developed significant DTH compared with CD40−/− and macrophage-depleted WT mice. This study demonstrated that CD40-induced IL-12 is required for generation of systemic Th1 immunity to nephritogenic Ags, and that IL-12 enhances Th1 effector cell recruitment to peripheral sites of Ag presentation via generation of local chemokines. Effector cell activation, renal DTH-like injury, and dermal DTH require direct Th1 CD154/macrophage CD40 interactions.
A Novel Therapy of Murine Collagen-Induced Arthritis with Soluble T1/ST2
Authors: Leung Bernard P. , Xu Damo , Culshaw Shauna , McInnes Iain B. , Liew Foo Y.
Published: April 2014

Rheumatoid arthritis is characterized by chronic inflammatory infiltration of the synovium, leading to eventual cartilage and bone destruction. Previously, we have reported that soluble T1/ST2 (sST2), a member of the IL-1R gene family, inhibits LPS-induced macrophage proinflammatory cytokine production. In this study, we report the therapeutic effect of sST2-Fc in the murine model of collagen-induced arthritis. A short term administration of sST2-Fc fusion protein significantly attenuated disease severity compared with controls treated with normal IgG. Histological examination revealed that while control IgG-treated mice developed severe cellular infiltration in the joints, synovial hyperplasia, and joint erosion, this pathology was profoundly reduced in sST2-Fc-treated animals. Treatment of sST2-Fc also down-regulated serum levels of IL-6, IL-12, and TNF-α. Spleen cells from the sST2-Fc-treated mice produced significantly less IFN-γ, TNF-α, IL-6, and IL-12 compared with cells from the control mice when cultured with collagen in vitro. Finally, pretreatment with ST2-Fc markedly inhibited the ability of human monocytic THP1 cells to release TNF-α when cocultured with peripheral blood T cells from rheumatoid patients. Together these results demonstrate that sST2-Fc may provide a novel approach in treating chronic autoimmune conditions by inhibiting the release of proinflammatory cytokines.
The Regulatory C-Terminal Determinants within Mycobacterial Heat Shock Protein 65 Are Cryptic and Cross-Reactive with the Dominant Self Homologs: Implications for the Pathogenesis of Autoimmune Arthritis
Authors: Durai Malarvizhi , Kim Hong Ro , Moudgil Kamal D.
Published: April 2014

The 65-kDa mycobacterial heat shock protein (Bhsp65) has been invoked in the pathogenesis of both adjuvant arthritis (AA) in the Lewis rat (RT.1l) and human rheumatoid arthritis. Arthritic Lewis rats in the late phase of AA show diversification of the T cell response to Bhsp65 C-terminal determinants (BCTD), and pretreatment of naive Lewis rats with a mixture of peptides representing these neoepitopes affords protection against AA. However, the fine specificity and physiologic significance of the BCTD-directed T cell repertoire, and the role of homologous self (rat) hsp65 (Rhsp65), if any, in spreading of the T cell response to Bhsp65 have not yet been examined. We observed that T cells primed by peptides comprising BCTD can adoptively transfer protection against AA to the recipient Lewis rats. However, these T cells can be activated by preprocessed (peptide) form of BCTD, but not native Bhsp65, showing that BCTD are cryptic epitopes. The BCTD-reactive T cells can be activated by the naturally generated (dominant) C-terminal epitopes of both exogenous and endogenous Rhsp65 and vice versa. Furthermore, certain individual peptides constituting BCTD and their self homologs can also induce protection against AA. These results support a model for the diversification of T cell response to Bhsp65 during the course of AA involving up-regulation of the display of cryptic BCTD coupled with spontaneous induction of T cell response to the cross-reactive dominant C-terminal epitopes of Rhsp65. The identification of disease-regulating cryptic determinants in Ags implicated in arthritis provides a novel approach for immunotherapy of rheumatoid arthritis.
Distinct Maturation of, but Not Migration between, Human Monocyte-Derived Dendritic Cells upon Ingestion of Apoptotic Cells of Early or Late Phases
Authors: Ip Wai-Kee , Lau Yu-Lung
Published: April 2014

Cell death via apoptosis is a normal physiological process. Rapid, but silent, removal of apoptotic cells (ACs) plays an essential role in maintaining homeostasis in the immune system. Defective clearance of ACs allows ACs to accumulate and undergo late phase apoptosis, also known as secondary necrosis, which may generate danger signals, leading to inflammation or autoimmunity. In this study we investigate the outcome of dendritic cells (DCs), which are potent APCs, on the interaction with ACs of early or late phase. Immature DCs internalized ACs of both early and late phases with similar efficiency. However, DCs that had taken up ACs of early phase acquired a non-fully mature DC phenotype, expressing low MHC class II complex, costimulatory molecule CD40, and mature DC-restricted marker CD83, and had a low capacity to stimulate allogeneic CD4+ T cell proliferation, whereas DCs that had taken up ACs of late phase acquired a mature DC phenotype with enhanced T cell stimulatory capacity. Ingestion of either early or late ACs induced minimal production of IL-12 and modulated CC chemokine and CCR expression in DCs. In particular, there was down-regulation of CCR5 and up-regulation of CCR7, resulting in switches in responsiveness from inflammatory to lymphoid chemokines. We conclude from these data that after taking up ACs of either early or late phases, DCs acquire the capability of homing to draining lymph nodes, and the distinct maturation between DCs taking up early or late ACs may contribute to DC function in the induction of T cell tolerance or Ag-specific T cell response, respectively.
Maintenance of Peritoneal B-1a Lymphocytes in the Absence of the Spleen
Authors: Kretschmer Karsten , Stopkowicz Jana , Scheffer Stephan , Greten Tim F. , Weiss Siegfried
Published: April 2014

Positive selection by autoantigens is believed to play an important role in the generation/maintenance of B-1a cells. Recently, it has been described that splenectomy results in the loss of an already established B-1a cell pool. To elucidate whether the spleen influences the peritoneal B-1a repertoire, we have analyzed the consequences of splenectomy in the recently established IgL-transgenic L2 mouse model. L2 mice are characterized by a severe block of B-2 development and predominance of B-1a cells, which exhibit a pronounced IgH oligoclonality, presumably due to positive selection by autoantigens. In this study, we show that, in striking contrast to splenectomized normal mice, L2 mice exhibit unchanged frequencies of peritoneal B-1a cells. The IgH repertoire of these B-1a cells, however, was severely perturbed in that the previously described predominant B-1a H chains were no longer present. The repertoire changes were partial since phosphatidylcholine-specific B-1a cells were present in similar numbers before and after splenectomy. Thus, splenic Ags appear to act as “survival factors” for major subsets of peritoneal B cells. The loss of B-1a cells in the absence of such factors is compensated by repertoire changes among B-1a cells in B cell lymphopenic L2 but not normal mice.
Reduction in the Developmental Potential of Intrathymic T Cell Progenitors with Age
Authors: Min Hyeyoung , Montecino-Rodriguez Encarnacion , Dorshkind Kenneth
Published: April 2014

Current models of thymic involution propose that intrinsic developmental defects in intrathymic T cell precursors do not contribute to age-related declines in thymopoiesis. This premise was reassessed in a murine model in light of the recent definition of the early T lineage progenitor (ETP), which appears to be the earliest intrathymic precursor defined to date. The results demonstrate that the frequency of ETP declines with age and their potential to reconstitute the thymus is diminished. These findings are consistent with the fact that ETP from aged mice proliferate less and have a higher rate of apoptosis than their counterparts from young animals. Taken together, these data suggest that age-associated changes in T cell precursors should be considered when attempts to rejuvenate the involuted thymus are made.
Expansion and Contraction of the NK Cell Compartment in Response to Murine Cytomegalovirus Infection
Authors: Robbins Scott H. , Tessmer Marlowe S. , Mikayama Toshifumi , Brossay Laurent
Published: April 2014

NK cells are capable of responding quickly to infectious challenge and contribute to the early defense against a wide variety of pathogens. Although the innate NK cell response to murine CMV (MCMV) has been extensively characterized, its resolution and the fate of the activated NK cell population remains unexplored. Herein, we characterize both the expansion and contraction phases of the NK cell response to MCMV. We demonstrate that NK cell recruitment into the immune response to MCMV infection is restricted to the first 3 days of infection and as the peripheral NK cell compartment expands, NK cells undergo accelerated phenotypic maturation. During the resolution of the immune response, NK cell compartmental contraction is marked by the selective death of responding NK cells. Additionally, throughout the infection, a naive NK cell pool that remains responsive to additional stimuli is actively maintained. These findings illustrate the plasticity of the NK cell compartment in response to pathogens and underscore the homeostatic maintenance of the resting peripheral NK cell pool.
Differential Regulatory Capacity of CD25+ T Regulatory Cells and Preactivated CD25+ T Regulatory Cells on Development, Functional Activation, and Proliferation of Th2 Cells
Authors: Stassen Michael , Jonuleit Helmut , Müller Christian , Klein Matthias , Richter Christoph , Bopp Tobias , Schmitt Steffen , Schmitt Edgar
Published: April 2014

CD25+ T regulatory (Treg) cells play a central role regarding the maintenance of peripheral tolerance via suppression of autoaggressive CD4+ T cells, CD8+ T cells, and Th1 cells. In this study we demonstrate that CD25+ Treg cells can also suppress the differentiation of murine conventional CD4+ T cells toward Th2 cells in a contact-dependent manner. However, the cytokine production and proliferation of established Th2 cells could not be inhibited by freshly isolated CD25+ Treg cells, whereas a strong inhibition of differentiated Th2 cells by in vitro preactivated CD25+ Treg cells could be observed. Inhibition of both conventional CD4+ T cells and Th2 cells is accompanied by a strong enhancement of the expression of FoxP3 in the suppressed T cells. Hence, our study indicates that CD25+ Treg cells have a therapeutic potential for Th2-mediated diseases and suggests a novel mechanism of suppression mediated by the transcriptional repressor FoxP3.