bluuebunny/crossref_metadata_2025 huggingface dataset:
HIV-Induced Changes in T Cell Signaling Pathways
Authors: Schweneker Marc , Favre David , Martin Jeffrey N. , Deeks Steven G. , McCune Joseph M.
Published: April 2014

Infection with HIV usually results in chronic activation of the immune system, with profound quantitative and qualitative changes in the T cell compartment. To better understand the mechanistic basis for T cell dysfunction and to discern whether such mechanisms are reversed after effective antiviral treatment, we analyzed changes in signaling pathways of human CD4+ and CD8+ T cells from 57 HIV-infected subjects in varying stages of disease progression and treatment, including long-term nonprogressors, progressors, and chronically infected subjects provided effective antiretroviral therapy (responders). A previously described PhosFlow method was adapted and optimized so that protein phosphorylation could be visualized in phenotypically defined subpopulations of CD4+ and CD8+ T cells (naive, memory, and effector) by flow cytometry. T cell signaling induced by TCR cross-linking, IL-2, or PMA/ionomycin was found to be blunted within all T cell subpopulations in those with progressive HIV disease compared with long-term nonprogressors and responders. Although alterations in cellular signaling correlated with levels of basal phosphorylation, viral load, and/or expression of programmed death-1, it was the level of basal phosphorylation that appeared to be the factor most dominantly associated with impaired signaling. Notably, provision of effective antiretroviral therapy was associated with a normalization of both basal phosphorylation levels and T cell signaling. These data, in aggregate, suggest that generalized dysfunction of the T cell compartment during progressive HIV disease may be in part dependent upon an increased basal level of phosphorylation, which itself may be due to the heightened state of immune activation found in advanced disease.
T Cell Ig and Mucin Domain-1-Mediated T Cell Activation Requires Recruitment and Activation of Phosphoinositide 3-Kinase
Authors: de Souza Anjali J. , Oak Jean S. , Jordanhazy Ryan , DeKruyff Rosemarie H. , Fruman David A. , Kane Lawrence P.
Published: April 2014

Ligation of the transmembrane protein T cell Ig and mucin domain (Tim)-1 can costimulate T cell activation. Agonistic Abs to Tim-1 are also capable of inducing T cell activation without additional stimuli. However, little is known about the biochemical mechanisms underlying T cell stimulation or costimulation through Tim-1. We show that a tyrosine in Tim-1 becomes phosphorylated in a lck-dependent manner, whereupon it can directly recruit p85 adaptor subunits of PI3K. This results in PI3K activation, which is required for Tim-1 function. We also provide genetic evidence that p85 expression is required for optimal Tim-1 function. Thus, we describe a pathway from Tim-1 tyrosine phosphorylation to the PI3K signaling pathway, which appears to be a major effector of Tim-1-mediated T cell activation.
Antiproliferative Activity of IL-27 on Melanoma
Authors: Yoshimoto Takayuki , Morishima Noriko , Mizoguchi Izuru , Shimizu Motomu , Nagai Hiroshi , Oniki Shuntaro , Oka Masahiro , Nishigori Chikako , Mizuguchi Junichiro
Published: April 2014

IL-27 is a member of the IL-6/IL-12 family and activates both STAT1 and STAT3 through its receptor, which consists of WSX-1 and gp130. We previously demonstrated that IL-27 has potent antitumor activities, which are mediated through CD8+ T cells, NK cells, or its own antiangiogenic activity. In this study, we demonstrate that IL-27 also possesses a direct antiproliferative activity on melanoma. Although WSX-1 expression was hardly detected in parental mouse melanoma B16F10 cells, IL-27 activated STAT1 and STAT3 and up-regulated MHC class I in B16F10 transfectants expressing wild-type WSX-1. In contrast, IL-27 failed to activate STAT1 and up-regulate MHC class I in those expressing mutant WSX-1, in which the putative STAT1-binding Tyr-609 of the cytoplasmic region was replaced by Phe. IL-27 inhibited the tumor growth of transfectants expressing wild-type WSX-1 in a dose-dependent manner. IL-27 augmented the expression of IFN regulatory factor (IRF)-1 and IRF-8, which possess tumor suppressor activities, in B16F10 transfectants expressing wild-type WSX-1. Down-regulation of IRF-1 but not IRF-8 with small interfering RNA partially blocked the IL-27-induced growth inhibition. A small, but significant, direct antiproliferative effect of IL-27 was also observed in vivo. Moreover, several human melanoma cells were revealed to express both IL-27 receptor subunits, and activation of STAT1 and STAT3 and growth inhibition by IL-27 were detected. These results suggest that IL-27 has an antiproliferative activity on melanomas through WSX-1/STAT1 signaling. Thus, IL-27 may be an attractive candidate as an antitumor agent applicable to cancer immunotherapy.
Preferential Costimulation by CD80 Results in IL-10-Dependent TGF-β1+-Adaptive Regulatory T Cell Generation
Authors: Perez Nicolas , Karumuthil-Melethil Subha , Li Ruobing , Prabhakar Bellur S. , Holterman Mark J. , Vasu Chenthamarakshan
Published: April 2014

Costimulatory ligands CD80 and CD86 have different binding preferences and affinities to their receptors, CD28 and CTLA-4. Earlier, we demonstrated that CD80 binds to CTLA-4 with higher affinity and has a role in suppressing T cell response. The current study demonstrates that not only did blockade of CD86 upon Ag presentation by bone marrow-derived dendritic cells (DC) to OVA-specific T cells result in induction of hyporesponsive T cells but also that these T cells could suppress the proliferative response of effector T cells. These T cells showed TGF-β1 on their surface and secreted TGF-β1 and IL-10 upon restimulation. Although blockade of CTLA-4 and neutralization of IL-10 profoundly inhibited the induction of these TGF-β1+ T cells, their ability to suppress the effector T cell proliferation was abrogated by neutralization of TGF-β1 alone. Induction of TGF-β1+ and IL-10+ T cells was found to be independent of natural CD4+CD25+ regulatory T cells, demonstrating that preferential ligation of CTLA-4 by CD80 induced IL-10 production by effector T cells, which in turn promoted the secretion of TGF-β1. Treatment of prediabetic NOD mice with islet β cell Ag-pulsed CD86−/− DCs, but not CD80−/− DCs, resulted in the induction of TGF-β1- and IL-10-producing cells, significant suppression of insulitis, and delay of the onset of hyperglycemia. These observations demonstrate not only that CD80 preferentially binds to CTLA-4 but also that interaction during Ag presentation can result in IL-10-dependent TGF-β1+ regulatory T cell induction, reinstating the potential of approaches to preferentially engage CTLA-4 through CD80 during self-Ag presentation in suppressing autoimmunity.
The Chemokine Receptor CXCR3 Is Degraded following Internalization and Is Replenished at the Cell Surface by De Novo Synthesis of Receptor
Authors: Meiser Andrea , Mueller Anja , Wise Emma L. , McDonagh Ellen M. , Petit Sarah J. , Saran Namita , Clark Peter C. , Williams Timothy J. , Pease James E.
Published: April 2014

The chemokine receptor CXCR3 is expressed on the surface of both resting and activated T lymphocytes. We describe in this study the endocytosis of CXCR3 using T lymphocytes and CXCR3 transfectants. Chemokine-induced CXCR3 down-regulation occurred in a rapid, dose-dependent manner, with CXCL11 the most potent and efficacious ligand. Endocytosis was mediated in part by arrestins, but appeared to occur independently of clathrin and caveolae. In contrast to other chemokine receptors, which are largely recycled to the cell surface within an hour, cell surface replenishment of CXCR3 occurred over several hours and was dependent upon mRNA transcription, de novo protein synthesis, and transport through the endoplasmic reticulum and Golgi. Confocal microscopy and Western blotting confirmed the fate of endocytosed CXCR3 to be degradation, mediated in part by lysosomes and proteosomes. Site-directed mutagenesis of the CXCR3 C terminus revealed that internalization and degradation were independent of phosphorylation, ubiquitination, or a conserved LL motif. CXCR3 was found to be efficiently internalized in the absence of ligand, a process involving a YXXL motif at the extreme of the C terminus. Although freshly isolated T lymphocytes expressed moderate cell surface levels of CXCR3, they were only responsive to CXCL11 with CXCL9 and CXCL10 only having significant activity on activated T lymphocytes. Thus, the activities of CXCR3 are tightly controlled following mRNA translation. Because CXCR3+ cells are themselves a source of IFN-γ, which potently induces the expression of CXCR3 ligands, such tight regulation of CXCR3 may serve as a control to avoid the unnecessary amplification of activated T lymphocyte recruitment.
Novel KIR3DL1 Alleles and Their Expression Levels on NK Cells: Convergent Evolution of KIR3DL1 Phenotype Variation?
Authors: Thomas Rasmi , Yamada Eriko , Alter Galit , Martin Maureen P. , Bashirova Arman A. , Norman Paul J. , Altfeld Marcus , Parham Peter , Anderson Stephen K. , McVicar Daniel W. , Carrington Mary
Published: April 2014

KIR3DL1 shows extensive polymorphism, and its variation has functional significance in terms of cell-surface expression levels and inhibitory capacity. We characterized nine KIR3DL1 alleles (*022, *028, *029, *033, *035, *051, *052, *053, and *054), four of which were identified for the first time in this study, and compared them to known alleles in phylogenetic analysis. Blood was available from eight individuals with these alleles, and cell-surface expression on NK cells could be determined for six of them using the KIR3DL1-specific Ab DX9. Four of the alleles were expressed at clearly detectable levels, and two others showed exceptionally low levels of expression. Site-directed mutagenesis demonstrated that single amino acid changes can result in either diminished or enhanced DX9 staining compared with the respective related KIR3DL1 allotypes. These results raise the possibility that KIR3DL1 evolution maintains variation in KIR3DL1 cell-surface expression levels, potentially due to the effect of such variation on functional capacity.
Increasing the CD4+ T Cell Precursor Frequency Leads to Competition for IFN-γ Thereby Degrading Memory Cell Quantity and Quality
Authors: Whitmire Jason K. , Benning Nicola , Eam Boreth , Whitton J. Lindsay
Published: April 2014

The precursor frequency of naive CD4+ T cells shows an inverse relationship with the number of memory cells generated after exposure to cognate Ag. Using the lymphocytic choriomeningitis virus (LCMV) model, we show here that only when the initial number of naive virus-specific CD4+ T cell precursors is low (≤104 per spleen) do they give rise to abundant and homogeneous memory cells that are CD62Llow, IL-7Rhigh, and imbued with an enhanced capacity to produce cytokine, proliferate, and survive over time. Furthermore, memory cells derived from a high naive precursor number show functional deficits upon secondary exposure to virus. The negative effect of higher naive precursor frequency was not attributable to competition for limiting amounts of Ag, because LCMV-naive CD4+ TCR-transgenic CD4 T cells were recruited into the LCMV-induced response even when their initial number was high. Instead, the T cells appear to compete for direct IFN-γ signals as they differentiate into memory cells. These results are consistent with a model of T cell development in which the most fit effector T cells that receive sufficient direct IFN-γ signals are selected to differentiate further into memory cells.
Early Resolution of Acute Immune Activation and Induction of PD-1 in SIV-Infected Sooty Mangabeys Distinguishes Nonpathogenic from Pathogenic Infection in Rhesus Macaques
Authors: Estes Jacob D. , Gordon Shari N. , Zeng Ming , Chahroudi Ann M. , Dunham Richard M. , Staprans Silvija I. , Reilly Cavan S. , Silvestri Guido , Haase Ashley T.
Published: April 2014

Primate lentiviruses are typically apathogenic in their evolutionarily coadapted host species but can be lethal when transferred to new host species. Why such infections are pathogenic in humans and rhesus macaques (RMs) but not in sooty mangabeys (SMs), a natural host, remains unclear. Studies of chronically infected animals point to the importance of diminished immune activation in response to the infection in SMs. In this study, we sought the causes and timing of the differences in immune activation in a comparative study of acute SIV infection in RMs and SMs. Surprisingly, we show that in acute infection immune activation is comparable in SMs and RMs but thereafter, SMs quickly resolve immune activation, whereas RMs did not. Early resolution of immune activation in SMs correlated with increased expression of PD-1 and with preservation of CD4+ T cell counts and lymphatic tissue architecture. These findings point to early control of immune activation by host immunoregulatory mechanisms as a major determinant of the different disease outcomes in SIV infection of natural vs non-natural hosts.
NAIP and Ipaf Control Legionella pneumophila Replication in Human Cells
Authors: Vinzing Maya , Eitel Julia , Lippmann Juliane , Hocke Andreas C. , Zahlten Janine , Slevogt Hortense , N′Guessan Philippe Dje , Günther Stefan , Schmeck Bernd , Hippenstiel Stefan , Flieger Antje , Suttorp Norbert , Opitz Bastian
Published: April 2014

In mice, different alleles of the mNAIP5 (murine neuronal apoptosis inhibitory protein-5)/mBirc1e gene determine whether macrophages restrict or support intracellular replication of Legionella pneumophila, and whether a mouse is resistant or (moderately) susceptible to Legionella infection. In the resistant mice strains, the nucleotide-binding oligomerization domain (Nod)-like receptor (NLR) family member mNAIP5/mBirc1e, as well as the NLR protein mIpaf (murine ICE protease-activating factor), are involved in recognition of Legionella flagellin and in restriction of bacterial replication. Human macrophages and lung epithelial cells support L. pneumophila growth, and humans can develop severe pneumonia (Legionnaires disease) after Legionella infection. The role of human orthologs to mNAIP5/mBirc1e and mIpaf in this bacterial infection has not been elucidated. Herein we demonstrate that flagellin-deficient L. pneumophila replicate more efficiently in human THP-1 macrophages, primary monocyte-derived macrophages, and alveolar macrophages, and in A549 lung epithelial cells compared with wild-type bacteria. Additionally, we note expression of the mNAIP5 ortholog hNAIP in all cell types examined, and expression of hIpaf in human macrophages. Gene silencing of hNAIP or hIpaf in macrophages or of hNAIP in lung epithelial cells leads to an enhanced bacterial growth, and overexpression of both molecules strongly reduces Legionella replication. In contrast to experiments with wild-type L. pneumophila, hNAIP or hIpaf knock-down affects the (enhanced) replication of flagellin-deficient Legionella only marginally. In conclusion, hNAIP and hIpaf mediate innate intracellular defense against flagellated Legionella in human cells.
Cutting Edge: Soluble IL-6R Is Produced by IL-6R Ectodomain Shedding in Activated CD4 T Cells
Authors: Briso Eva M. , Dienz Oliver , Rincon Mercedes
Published: April 2014

IL-6 trans-signaling via the soluble IL-6R (sIL-6R) plays an important role in the progression of several autoimmune diseases and cancer by providing IL-6-responsiveness to cells lacking IL-6R. However, the potential sources of sIL-6R are less understood. In this study we show that sIL-6R is produced by both naive and memory CD4 T cells upon TCR activation. The production of sIL-6R by activated CD4 T cells is mediated by shedding of the membrane-bound IL-6R, and this process correlates with the expression of the metalloproteinase ADAM17 in these cells. In contrast to CD4 T cells, CD8 T cells do not express ADAM17 and their production of sIL-6R is negligible. Thus, during an immune response CD4 T cells are an important source of sIL-6R. Production of sIL-6R by autoreactive CD4 T cells may contribute to their role in the development of autoimmune disease by conferring IL-6-responsiveness to cells lacking IL-6R such as synoviocytes.
Both Radioresistant and Hemopoietic Cells Promote Innate and Adaptive Immune Responses to Flagellin
Authors: Sanders Catherine J. , Moore Daniel A. , Williams Ifor R. , Gewirtz Andrew T.
Published: April 2014

The TLR5 agonist flagellin induces innate and adaptive immune responses in a MyD88-dependent manner and is under development as a vaccine adjuvant. In vitro studies indicate that, compared with other bacteria-derived adjuvants, flagellin is a very potent activator of proinflammatory gene expression and cytokine production from cells of nonhemopoietic origin. However, the role of nonhemopoietic cells in promoting flagellin-induced immune responses in vivo remains unclear. To investigate the relative contributions of the nonhemopoietic (radioresistant) and the hemopoietic (radiosensitive) compartments, we measured both innate and adaptive immune responses of flagellin-treated MyD88 radiation bone marrow chimeras. We observed that radiosensitive and radioresistant cells played distinct roles in the innate response to flagellin, with the radiosensitive cells producing the majority of the TNF-α, IL-12, and IL-6 cytokines and the radioresistant cells most of the KC, IP-10, and MCP-1 cytokines. Direct activation of either compartment alone by flagellin initiated dendritic cell costimulatory molecule up-regulation and induced a significant humoral immune response to the protein itself as well as to coinjected OVA. However, robust humoral responses were only observed when MyD88 was present in both cell compartments. Further studies revealed that hemopoietic and nonhemopoietic expression of the cytokines TNF-α and IL-6, but not IL-1, played an important role in promoting flagellin-induced Ab responses. Thus, in vivo both radioresistant and hemopoietic cells play key nonredundant roles in mediating innate and adaptive immune responses to flagellin.
Late Expression of Granulysin by Microbicidal CD4+ T Cells Requires PI3K- and STAT5-Dependent Expression of IL-2Rβ That Is Defective in HIV-Infected Patients
Authors: Zheng Chun Fu , Jones Gareth J. , Shi Meiqing , Wiseman Jeremy C. D. , Marr Kaleb J. , Berenger Byron M. , Huston Shaunna M. , Gill M. John , Krensky Alan M. , Kubes Paul , Mody Christopher H.
Published: April 2014

Granulysin is a cytolytic effector molecule used by lymphocytes to kill tumor and microbial cells. Regulation of granulysin production is complex. A significant delay (5 days) following stimulation of CD4+ T cells with IL-2 occurs before granulysin is produced. Unfortunately, the mechanisms responsible for this delay are unknown. We have recently demonstrated that granulysin-mediated killing of Cryptococcus neoformans by CD4+ T cells is defective during HIV infection. This is because CD4+ T cells from HIV-infected patients fail to produce granulysin in response to IL-2 activation. The present studies examined the mechanism of delayed production of granulysin and the mechanism of the defect in HIV patients. We demonstrate that IL-2 initially requires both STAT5 and PI3K activation to increase expression of IL-2Rβ, produce granulysin, and kill C. neoformans. The increased expression of IL-2Rβ precedes granulysin, and preventing the increased expression of IL-2Rβ using small interfering RNA knockdown abrogates granulysin expression. Moreover, following the increased expression of IL-2Rβ, blocking subsequent signaling by IL-2 using IL-2Rβ-specific blocking Abs abrogates expression of granulysin. Finally, CD4+ T cells from HIV-infected patients, who are defective in both STAT5 and PI3K signaling, fail to express IL-2Rβ and fail to produce granulysin. These results suggest that IL-2 signals via PI3K and STAT5 to increase expression of IL-2Rβ, which in turn is required for production of granulysin. These results provide a mechanism to explain the “late” production of granulysin during normal T cell responses, as well as for defective granulysin production by CD4+ T cells in HIV-infected patients.
The Macrophage-Inducible C-Type Lectin, Mincle, Is an Essential Component of the Innate Immune Response to Candida albicans
Authors: Wells Christine A. , Salvage-Jones Judith A. , Li Xin , Hitchens Kelly , Butcher Suzanne , Murray Rachael Z. , Beckhouse Anthony G. , Lo Yu-Lan-Sandra , Manzanero Silvia , Cobbold Christian , Schroder Kate , Ma Bo , Orr Sally , Stewart Lauren , Lebus Daniel , Sobieszczuk Peter , Hume David A. , Stow Jennifer , Blanchard Helen , Ashman Robert B.
Published: April 2014

The recognition of carbohydrate moieties by cells of the innate immune system is emerging as an essential element in antifungal immunity, but despite the number and diversity of lectins expressed by innate immune cells, few carbohydrate receptors have been characterized. Mincle, a C-type lectin, is expressed predominantly on macrophages, and is here shown to play a role in macrophage responses to the yeast Candida albicans. After exposure to the yeast in vitro, Mincle localized to the phagocytic cup, but it was not essential for phagocytosis. In the absence of Mincle, production of TNF-α by macrophages was reduced, both in vivo and in vitro. In addition, mice lacking Mincle showed a significantly increased susceptibility to systemic candidiasis. Thus, Mincle plays a novel and nonredundant role in the induction of inflammatory signaling in response to C. albicans infection.
Genetic Differences in Bone Marrow-Derived Lymphoid Lineages Control Susceptibility to Experimental Autoimmune Myocarditis
Authors: Li Haiyan S. , Ligons Davinna L. , Rose Noel R. , Guler Mehmet L.
Published: April 2014

Bone marrow (BM) transplantation has been used to study the cellular basis of genetic control of autoimmune diseases, but conclusions remain elusive due to the contradictory findings in different animal models. In the current study, we found that BM cells from myocarditis-susceptible A.SW mice can render irradiated, myocarditis-resistant B10.S recipient mice susceptible to myosin-induced myocarditis, indicating that hematopoietic cells express the genetic differences controlling susceptibility to autoimmune myocarditis. We then sought to differentiate the role of lymphoid vs nonlymphoid components of BM in the pathogenesis of myocarditis by comparing mixed chimeras receiving BM from A.SW wild-type or RAG−/− mice mixed with BM from B10.S wild-type mice. This experiment clearly demonstrated that T and B lymphocytes were indispensable for transferring the susceptible phenotype to disease-resistant recipients. Our findings significantly narrow the cellular expression of genetic polymorphisms controlling the EAM phenotype.
Glycoprotein-Dependent and TLR2-Independent Innate Immune Recognition of Herpes Simplex Virus-1 by Dendritic Cells
Authors: Reske Adi , Pollara Gabriele , Krummenacher Claude , Katz David R. , Chain Benjamin M.
Published: April 2014

Innate immune recognition is an important early event in the host response to herpes simplex virus-1 (HSV-1) infection. Dendritic cells (DC) play an important sentinel role in this recognition. Previous studies have shown that monocyte-derived DC (MDDC) respond to HSV-1 by up-regulation of costimulatory molecules and type I IFN release, but the molecular targets on the virus recognized by the DC have not been defined. In this study we show that MDDC recognize and respond to the four essential viral glycoproteins, gB, gD, and gHgL, independent of other viral proteins or nucleic acids. DC recognition of these four glycoproteins leads to the up-regulation of CD40, CD83, CD86, and HLA-DR and to the production of IFN-α and IL-10, but not IL-12p70. Glutaraldehyde-fixation and nonfunctional gH mutants were used to show that recognition of glycoproteins does not require membrane fusion. The nature of the recognition event was probed further by transfecting glycoproteins individually or in combination, by blocking individual proteins with Abs, or by using mutant gD constructs unable to bind to their known cognate receptors. Unexpectedly, MDDC responses were found to require expression of all four glycoproteins. Furthermore, gD mutants that cannot bind nectin-1 and/or herpesvirus entry mediator can still induce DC maturation. Finally, although HSV-1 can signal via the TLR2 receptor, this receptor does not mediate recognition of glycoproteins. Thus, the complex of the four essential HSV-1 entry glycoproteins on the cell surface can provide a target for innate immune recognition of this virus.
Properdin Binds to Late Apoptotic and Necrotic Cells Independently of C3b and Regulates Alternative Pathway Complement Activation
Authors: Xu Wei , Berger Stefan P. , Trouw Leendert A. , de Boer Hetty C. , Schlagwein Nicole , Mutsaers Chantal , Daha Mohamed R. , van Kooten Cees
Published: April 2014

Cells that undergo apoptosis or necrosis are promptly removed by phagocytes. Soluble opsonins such as complement can opsonize dying cells, thereby promoting their removal by phagocytes and modulating the immune response. The pivotal role of the complement system in the handling of dying cells has been demonstrated for the classical pathway (via C1q) and lectin pathway (via mannose-binding lectin and ficolin). Herein we report that the only known naturally occurring positive regulator of complement, properdin, binds predominantly to late apoptotic and necrotic cells, but not to early apoptotic cells. This binding occurs independently of C3b, which is additional to the standard model wherein properdin binds to preexisting clusters of C3b on targets and stabilizes the convertase C3bBb. By binding to late apoptotic or necrotic cells, properdin serves as a focal point for local amplification of alternative pathway complement activation. Furthermore, properdin exhibits a strong interaction with DNA that is exposed on the late stage of dying cells. Our data indicate that direct recognition of dying cells by properdin is essential to drive alternative pathway complement activation.
Acute Lung Injury Induced by Lipopolysaccharide Is Independent of Complement Activation
Authors: Rittirsch Daniel , Flierl Michael A. , Day Danielle E. , Nadeau Brian A. , McGuire Stephanie R. , Hoesel Laszlo M. , Ipaktchi Kyros , Zetoune Firas S. , Sarma J. Vidya , Leng Lin , Huber-Lang Markus S. , Neff Thomas A. , Bucala Richard , Ward Peter A.
Published: April 2014

Although acute lung injury (ALI) is an important problem in humans, its pathogenesis is poorly understood. Airway instillation of bacterial LPS, a known complement activator, represents a frequently used model of ALI. In the present study, pathways in the immunopathogenesis of ALI were evaluated. ALI was induced in wild-type, C3−/−, and C5−/− mice by airway deposition of LPS. To assess the relevant inflammatory mediators, bronchoalveolar lavage fluids were evaluated by ELISA analyses and various neutralizing Abs and receptor antagonists were administered in vivo. LPS-induced ALI was neutrophil-dependent, but it was not associated with generation of C5a in the lung and was independent of C3, C5, or C5a. Instead, LPS injury was associated with robust generation of macrophage migration inhibitory factor (MIF), leukotriene B4 (LTB4), and high mobility group box 1 protein (HMGB1) and required engagement of receptors for both MIF and LTB4. Neutralization of MIF or blockade of the MIF receptor and/or LTB4 receptor resulted in protection from LPS-induced ALI. These findings indicate that the MIF and LTB4 mediator pathways are involved in the immunopathogenesis of LPS-induced experimental ALI. Most strikingly, complement activation does not contribute to the development of ALI in the LPS model.
The Mer Receptor Tyrosine Kinase Is Required for the Loss of B Cell Tolerance in the Chronic Graft-versus-Host Disease Model of Systemic Lupus Erythematosus
Authors: Shao Wen-Hai , Eisenberg Robert A. , Cohen Philip L.
Published: April 2014

The Mer receptor tyrosine kinase mediates apoptotic cell phagocytosis and modulates macrophage cytokine production. Mer−/− mice have defective clearance of apoptotic debris and develop a systemic lupus erythematosus-like autoimmune syndrome. It was surprising then that B6-Mer−/− recipients of bm12 spleen cells failed to develop anti-dsDNA and anti-chromatin autoantibodies, whereas B6 hosts produced the expected autoimmune chronic graft-vs-host (cGVH) reaction. The lack of autoantibody formation in cGVH was not due to the failure of Mer-deficient hosts to provoke alloreactivity, because Mer−/− spleen cells were recognized by bm12 T cells in MLR. Cell transfer experiments in Rag-knockout mice indicated that the lack of autoantibody production in Mer−/− cGVH disease hosts was due to an intrinsic B cell defect. This defect did not cause a global inability to produce autoantibodies, because in vivo exposure to LPS stimulated production of autoantibodies in both B6 and Mer−/− mice. We further observed that wild-type B6 B cells up-regulated Mer upon activation in cGVH, and that B cells from mice lacking Mer showed a decreased up-regulation of activation-associated cell surface markers. These findings indicate that Mer serves an important role in the activation of self-reactive B cells in systemic autoimmunity.
Lysophospholipids and ATP Mutually Suppress Maturation and Release of IL-1β in Mouse Microglial Cells Using a Rho-Dependent Pathway
Authors: Takenouchi Takato , Iwamaru Yoshifumi , Sugama Shuei , Sato Mitsuru , Hashimoto Makoto , Kitani Hiroshi
Published: April 2014

The P2X7 receptor (P2X7R), an ATP-gated ion channel, plays essential roles in the release and maturation of IL-1β in microglial cells in the brain. Previously, we found that lysophosphatidylcholine (LPC) potentiated P2X7R-mediated intracellular signals in microglial cells. In this study, we determined whether the lysophospholipids, i.e., LPC and sphingosylphosphorylcholine (SPC), modulate the ATP-induced release and processing of IL-1β mediated by P2X7R in mouse MG6 microglial cells. LPC or SPC alone induced the release of precursor (pro-IL-1β) and mature IL-1β (mIL-1β) from LPS-primed MG6 cells, possibly due to lytic functions. However, these lysophospholipids inhibited ATP-induced caspase-1 activation that is usually followed by the release of mIL-1β. Conversely, ATP inhibited the release of pro-IL-1β and mIL-1β induced by LPC/SPC. This suggests that lysophospholipids and ATP mutually suppressed each function to release IL-1β. P2X7R activation resulted in microtubule reorganization in the MG6 cells that was blocked in the presence of LPC and SPC. LPC/SPC reduced the amount of activated RhoA after stimulation with ATP, implying that these lysophospholipids block ATP-induced microtubule reorganization by interfering with RhoA activation. In addition, the microtubule inhibitor colchicine inhibited ATP-induced release of mIL-1β similar to that of LPC and SPC. This suggests that the impairment of the microtubule reassembly may be associated with the inhibitory effects of LPC/SPC on ATP-induced mIL-1β release. Mutual suppression by ATP and LPC/SPC on the maturation of IL-1β was observed in LPS-primed primary microglia. Collectively, these data suggest opposing functions by lysophospholipids, either proinflammatory or anti-inflammatory, in regard to the maturation and release of IL-1β from microglial cells.
IFN-γ and STAT1 Arrest Monocyte Migration and Modulate RAC/CDC42 Pathways
Authors: Hu Yang , Hu Xiaoyu , Boumsell Laurence , Ivashkiv Lionel B.
Published: April 2014

Positive regulation of cell migration by chemotactic factors and downstream signaling pathways has been extensively investigated. In contrast, little is known about factors and mechanisms that induce migration arrest, a process important for retention of cells at inflammatory sites and homeostatic regulation of cell trafficking. In this study, we found that IFN-γ directly inhibited monocyte migration by suppressing remodeling of the actin cytoskeleton and cell polarization in response to the chemokine CCL2. Inhibition was dependent on STAT1 and downstream genes, whereas STAT3 promoted migration. IFN-γ altered monocyte responses to CCL2 by modulating the activity of Pyk2, JNK, and the GTPases Rac and Cdc42, and inhibiting CCL2-induced activation of the downstream p21-activated kinase that regulates the cytoskeleton and cell polarization. These results identify a new role for IFN-γ in arresting monocyte chemotaxis by a mechanism that involves modulation of cytoskeleton remodeling. Crosstalk between Jak-STAT and Rac/Cdc42 GTPase-mediated signaling pathways provides a molecular mechanism by which cytokines can regulate cell migration.
c-Rel Is Essential for the Development of Innate and T Cell-Induced Colitis
Authors: Wang Yanyan , Rickman Barry H. , Poutahidis Theofilos , Schlieper Katherine , Jackson Erin A. , Erdman Susan E. , Fox James G. , Horwitz Bruce H.
Published: April 2014

Inflammatory bowel disease is a chronic inflammatory response of the gastrointestinal tract mediated in part by an aberrant response to intestinal microflora. Expression of IL-23 subunits p40 and p19 within cells of the innate immune system plays a central role in the development of lower bowel inflammation in response inflammatory challenge. The NF-κB subunit c-Rel can regulate expression of IL-12/23 subunits suggesting that it could have a critical role in mediating the development of chronic inflammation within the lower bowel. In this study, we have analyzed the role of c-Rel within the innate immune system in the development of lower bowel inflammation, in two well-studied models of murine colitis. We have found that the absence of c-Rel significantly impaired the ability of Helicobacter hepaticus to induce colitis upon infection of RAG-2-deficient mice, and ameliorated the ability of CD4+CD45RBhigh T cells to induce disease upon adoptive transfer into RAG-deficient mice. The absence of c-Rel interfered with the expression of IL-12/23 subunits both in cultured primary macrophages and within the colon. Thus, c-Rel plays a critical role in regulating the innate inflammatory response to microflora within the lower bowel, likely through its ability to modulate expression of IL-12/23 family members.
Tolerization of a Type I Allergic Immune Response through Transplantation of Genetically Modified Hematopoietic Stem Cells
Authors: Baranyi Ulrike , Linhart Birgit , Pilat Nina , Gattringer Martina , Bagley Jessamyn , Muehlbacher Ferdinand , Iacomini John , Valenta Rudolf , Wekerle Thomas
Published: April 2014

Allergy represents a hypersensitivity disease that affects >25% of the population in industrialized countries. The underlying type I allergic immune reaction occurs in predisposed atopic individuals in response to otherwise harmless Ags (i.e., allergens) and is characterized by the production of allergen-specific IgE, an allergen-specific T cell response, and the release of biologically active mediators such as histamine from mast cells and basophils. Regimens permanently tolerizing an allergic immune response still need to be developed. We therefore retrovirally transduced murine hematopoietic stem cells to express the major grass pollen allergen Phl p 5 on their cell membrane. Transplantation of these genetically modified hematopoietic stem cells led to durable multilineage molecular chimerism and permanent immunological tolerance toward the introduced allergen at the B cell, T cell, and effector cell levels. Notably, Phl p 5-specific serum IgE and IgG remained undetectable, and T cell nonresponsiveness persisted throughout follow-up (40 wk). Besides, mediator release was specifically absent in in vitro and in vivo assays. B cell, T cell, and effector cell responses to an unrelated control allergen (Bet v 1) were unperturbed, demonstrating specificity of this tolerance protocol. We thus describe a novel cell-based strategy for the prevention of allergy.
ALeishmaniaOrtholog of Macrophage Migration Inhibitory Factor Modulates Host Macrophage Responses
Authors: Kamir Daniela , Zierow Swen , Leng Lin , Cho Yoonsang , Diaz Yira , Griffith Jason , McDonald Courtney , Merk Melanie , Mitchell Robert A. , Trent John , Chen Yibang , Kwong Yuen-Kwan Amy , Xiong Huabao , Vermeire Jon , Cappello Michael , McMahon-Pratt Diane , Walker John , Bernhagen Jurgen , Lolis Elias , Bucala Richard
Published: April 2014

Parasitic organisms have evolved specialized strategies to evade immune defense mechanisms. We describe herein an ortholog of the cytokine, macrophage migration inhibitory factor (MIF), which is produced by the obligate intracellular parasite, Leishmania major. The Leishmania MIF protein, Lm1740MIF, shows significant structural homology with human MIF as revealed by a high-resolution x-ray crystal structure (1.03 Å). Differences between the two proteins in the N-terminal tautomerization site are evident, and we provide evidence for the selective, species-specific inhibition of MIF by small-molecule antagonists that target this site. Lm1740MIF shows significant binding interaction with the MIF receptor, CD74 (Kd = 2.9 × 10−8 M). Like its mammalian counterpart, Lm1740MIF induces ERK1/2 MAP kinase activation in a CD74-dependent manner and inhibits the activation-induced apoptosis of macrophages. The ability of Lm1740MIF to inhibit apoptosis may facilitate the persistence of Leishmania within the macrophage and contribute to its evasion from immune destruction.
Pattern of Proinflammatory Cytokine Induction in RAW264.7 Mouse Macrophages Is Identical for Virulent and AttenuatedBorrelia burgdorferi
Authors: Wang Guiqing , Petzke Mary M. , Iyer Radha , Wu Hongyan , Schwartz Ira
Published: April 2014

Lyme disease pathogenesis results from a complex interaction between Borrelia burgdorferi and the host immune system. The intensity and nature of the inflammatory response of host immune cells to B. burgdorferi may be a determining factor in disease progression. Gene array analysis was used to examine the expression of genes encoding cytokines, chemokines, and related factors in the joint tissue of infected C3H/HeJ mice and in a murine macrophage-like cell line in response to a disseminating or attenuated clinical isolate of B. burgdorferi. Both isolates elicited a robust proinflammatory response in RAW264.7 cells characterized by an increase in transcript levels of genes encoding CC and CXC chemokines, proinflammatory cytokines, and TNF superfamily members. Transcription of genes encoding IL-1β, IL-6, MCP-1, MIP-1α, CXCR4, and TLR2 induced in RAW264.7 cells by either live or heat-killed spirochetes did not differ significantly at any time point over a 24-h period, nor was there a difference in the protein levels of IL-10, TNF-α, IL-6, and IL-12p70 in culture supernatants. Thus, induction of host macrophage expression of proinflammatory mediators by host macrophages does not contribute to the differential pathogenicity of different B. burgdorferi strains.
Role of the RNA-Binding Protein Tristetraprolin in Glucocorticoid-Mediated Gene Regulation
Authors: Ishmael Faoud T. , Fang Xi , Galdiero Maria Rosaria , Atasoy Ulus , Rigby William F. C. , Gorospe Myriam , Cheadle Chris , Stellato Cristiana
Published: April 2014

Glucocorticoids (GCs) are the mainstay of anti-inflammatory therapy. Modulation of posttranscriptional regulation (PTR) of gene expression by GCs is a relevant yet poorly characterized mechanism of their action. The RNA-binding protein tristetraprolin (TTP) plays a central role in PTR by binding to AU-rich elements in the 3′-untranslated region of proinflammatory transcripts and accelerating their decay. We found that GCs induce TTP expression in primary and immortalized human bronchial epithelial cells. To investigate the importance of PTR and the role of TTP in GC function, we compared the effect of GC treatment on genome-wide gene expression using mouse embryonic fibroblasts (MEFs) obtained from wild-type and TTP−/− mice. We confirmed that GCs induce TTP in MEFs and observed in TTP−/− MEFs a striking loss of up to 85% of GC-mediated gene expression. Gene regulation by TNF-α was similarly affected, as was the antagonistic effect of GC on TNF-α-induced response. Inflammatory genes, including cytokines and chemokines, were among the genes whose sensitivity to GCs was affected by lack of TTP. Silencing of TTP in WT MEFs by small interfering RNA confirmed loss of GC response in selected targets. Immunoprecipitation of ribonucleoprotein complexes revealed binding of TTP to several validated transcripts. Changes in the rate of transcript degradation studied by actinomycin D were documented for only a subset of transcripts bound to TTP. These results reveal a strong and previously unrecognized contribution of PTR to the anti-inflammatory action of GCs and point at TTP as a key factor mediating this process through a complex mechanism of action.
CD4+ T Cells Target Epitopes Residing within the RNA-Binding Domain of the U1-70-kDa Small Nuclear Ribonucleoprotein Autoantigen and Have Restricted TCR Diversity in an HLA-DR4-Transgenic Murine Model of Mixed Connective Tissue Disease
Authors: Greidinger Eric L. , Zang Yun Juan , Jaimes Kimberly , Martinez Laisel , Nassiri Mehdi , Hoffman Robert W.
Published: April 2014

Mixed connective tissue disease (MCTD) is a systemic autoimmune disease with significant morbidity and premature mortality of unknown pathogenesis. In the present study, we characterized U1-70-kDa small nuclear ribonucleoprotein (70-kDa) autoantigen-specific T cells in a new murine model of MCTD. These studies defined 70-kDa-reactive T cell Ag fine specificities and TCR gene usage in this model. Similar to patients with MCTD, CD4+ T cells can be readily identified from 70-kDa/U1-RNA-immunized HLA-DR4-transgenic mice. Using both freshly isolated CD4+ T cells from spleen and lung, and T cell lines, we found that the majority of these T cells were directed against antigenic peptides residing within the RNA-binding domain of 70 kDa. We also found that TCR-β (TRB) V usage was highly restricted among 70-kDa-reactive T cells, which selectively used TRBV subgroups 1, 2, 6, 8.1, 8.2, and 8.3, and that the TRB CDR3 had conserved sequence motifs which were shared across different TRBV subgroups. Finally, we found that the TRBV and CDR3 regions used by both murine and human 70-kDa-specific CD4+ T cells were homologous. Thus, T cell recognition of the 70-kDa autoantigen by HLA-DR4-transgenic mice is focused on a limited number of T cell epitopes residing primarily within the RBD of the molecule, using a restricted number of TRBV and CDR3 motifs that are homologous to T cells isolated from MCTD patients.
Distinct Structural Requirements of GATA-3 for the Regulation of Thymocyte and Th2 Cell Differentiation
Authors: Pai Sung-Yun , Kang Bok Yun , Sabadini Amelia M. , Parisini Emilio , Truitt Morgan L. , Ho I-Cheng
Published: April 2014

GATA-3, the only T cell-specific member of the GATA family of transcription factors, is essential for the intrathymic development of CD4+ T cells and for the differentiation of Th2 cells. However, whether distinct biochemical features, unique to GATA-3 compared with other GATA family members, are required to drive T cell transcriptional programs or whether the T cell-specific functions of GATA-3 can simply be ascribed to its expression pattern is unclear. Nor do we understand the protein structural requirements for each individual function of GATA-3. In this study, we report that a heterologous GATA factor, GATA-4, was competent in supporting the development of CD4+ T cells but could not fully compensate for GATA-3 in regulating the expression of Th cytokines. Specifically, GATA-3 was more potent than GATA-4 in driving the production of IL-13 due to a mechanism independent of DNA binding or chromatin remodeling of the IL-13 locus. The difference was mapped to a partially conserved region C-terminal to the second zinc finger. Converting a single proline residue located in this region of GATA-4 to its counterpart, a methionine of GATA-3, was sufficient to enhance the IL-13-promoting function of GATA-4 but had no effect on other cytokines. Taken together, our data demonstrate that the unique function of GATA-3 is conferred by both its cell type-specific expression and distinct protein structure.
Differential Activation of Human TLR4 by Escherichia coli and Shigella flexneri 2a Lipopolysaccharide: Combined Effects of Lipid A Acylation State and TLR4 Polymorphisms on Signaling
Authors: Rallabhandi Prasad , Awomoyi Agnes , Thomas Karen E. , Phalipon Armelle , Fujimoto Yukari , Fukase Koichi , Kusumoto Shoichi , Qureshi Nilofer , Sztein Marcelo B. , Vogel Stefanie N.
Published: April 2014

The lipid A of LPS activates TLR4 through an interaction with myeloid differentiation protein-2 (MD-2) and the degree of lipid A acylation affects TLR4 responsiveness. Two TLR4 single nucleotide polymorphisms (Asp299Gly and Thr399Ile) have been associated with LPS hyporesponsiveness. We hypothesized that the combination of hypoacylation and these single nucleotide polymorphisms would exhibit a compounded effect on TLR4 signaling. HEK293T transfectants expressing wild-type or polymorphic TLR4 were stimulated with Escherichia coli (predominantly hexaacylated lipid A) or Shigella flexneri 2a (a mixture of hexaacylated, pentaacylated, and predominantly tetraacylated lipid A) LPS, or hexaacylated vs pentaacylated synthetic lipid As. NF-κB-reporter activity was significantly lower in response to S. flexneri 2a than E. coli LPS and further decreased in polymorphic transfectants. Neither hexaacylated nor pentaacylated synthetic lipid A induced NF-κB activity in wild-type transfectants under the identical transfection conditions used for LPS; however, increasing human MD-2 expression rescued responsiveness to hexaacylated lipid A only, while murine MD-2 was required to elicit a response to pentaacylated lipid A. Adherent PBMC of healthy volunteers were also compared for LPS-induced TNF-α, IL-6, IL-1β, and IL-10 production. Cytokine levels were significantly lower (∼20–90%) in response to S. flexneri than to E. coli LPS/lipid A and PBMC from polymorphic individuals secreted decreased cytokine levels in response to both LPS types and failed to respond to pentaacylated lipid A. Thus, the combination of acylation state and host genetics may significantly impact vaccine immunogenicity and/or efficacy, whether LPS is an integral component of a whole organism vaccine or included as an adjuvant.
Syk Associates with Clathrin and Mediates Phosphatidylinositol 3-Kinase Activation during Human Rhinovirus Internalization
Authors: Lau Christine , Wang Xiaomin , Song Lihua , North Michelle , Wiehler Shahina , Proud David , Chow Chung-Wai
Published: April 2014

Human rhinovirus (HRV) causes the common cold. The most common acute infection in humans, HRV is a leading cause of exacerbations of asthma and chronic obstruction pulmonary disease because of its ability to exacerbate airway inflammation by altering epithelial cell biology upon binding to its receptor, ICAM-1. ICAM-1 regulates not only viral entry and replication but also signaling pathways that lead to inflammatory mediator production. We recently demonstrated the Syk tyrosine kinase to be an important mediator of HRV-ICAM-1 signaling: Syk regulates replication-independent p38 MAPK activation and IL-8 expression. In leukocytes, Syk regulates receptor-mediated internalization via PI3K. Although PI3K has been shown to regulate HRV-induced IL-8 expression and clathrin-mediated endocytosis of HRV, the role of airway epithelial Syk in this signaling pathway is not known. We postulated that Syk regulates PI3K activation and HRV endocytosis in the airway epithelium. Using confocal microscopy and immunoprecipitation, we demonstrated recruitment of the normally cytosolic Syk to the plasma membrane upon HRV16-ICAM-1 binding, along with Syk-clathrin coassociation. Subsequent incubation at 37°C to permit internalization revealed redistribution of Syk to punctate structures resembling endosomes and colocalization with HRV16. Internalized HRV was not detected in cells overexpressing the kinase inactive SykK396R mutant, indicating that kinase activity was necessary for endocytosis. HRV-induced PI3K activation was dependent on Syk; Syk knockdown by small interfering RNA significantly decreased phosphorylation of the PI3K substrate Akt. Together, these data reveal Syk to be an important mediator of HRV endocytosis and HRV-induced PI3K activation.