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1-20 of 26
Alan Sher
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Journal Articles
In Special Collection:
2019: The Year in Experimental Medicine
,
Innate Immune Sensors in Health and Disease
Eduardo P. Amaral, Diego L. Costa, Sivaranjani Namasivayam, Nicolas Riteau, Olena Kamenyeva, Lara Mittereder, Katrin D. Mayer-Barber, Bruno B. Andrade, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2019) 216 (3): 556–570.
Published: 20 February 2019
Abstract
Necrotic cell death during Mycobacterium tuberculosis (Mtb) infection is considered host detrimental since it facilitates mycobacterial spread. Ferroptosis is a type of regulated necrosis induced by accumulation of free iron and toxic lipid peroxides. We observed that Mtb-induced macrophage necrosis is associated with reduced levels of glutathione and glutathione peroxidase-4 (Gpx4), along with increased free iron, mitochondrial superoxide, and lipid peroxidation, all of which are important hallmarks of ferroptosis. Moreover, necrotic cell death in Mtb-infected macrophage cultures was suppressed by ferrostatin-1 (Fer-1), a well-characterized ferroptosis inhibitor, as well as by iron chelation. Additional experiments in vivo revealed that pulmonary necrosis in acutely infected mice is associated with reduced Gpx4 expression as well as increased lipid peroxidation and is likewise suppressed by Fer-1 treatment. Importantly, Fer-1–treated infected animals also exhibited marked reductions in bacterial load. Together, these findings implicate ferroptosis as a major mechanism of necrosis in Mtb infection and as a target for host-directed therapy of tuberculosis.
Includes: Supplementary data
Journal Articles
Difeng Fang, Kairong Cui, Kairui Mao, Gangqing Hu, Rao Li, Mingzhu Zheng, Nicolas Riteau, Steven L. Reiner, Alan Sher, Keji Zhao, Jinfang Zhu
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2018) 215 (11): 2705–2714.
Published: 19 September 2018
Abstract
T follicular helper (Tfh) cells express transcription factor BCL-6 and cytokine IL-21. Mature Tfh cells are also capable of producing IFN-γ without expressing the Th1 transcription factor T-bet. Whether this IFN-γ–producing Tfh population represents a unique Tfh subset with a distinct differentiation pathway is poorly understood. By using T-bet fate–mapping mouse strains, we discovered that almost all the IFN-γ–producing Tfh cells have previously expressed T-bet and express high levels of NKG2D. DNase I hypersensitivity analysis indicated that the Ifng gene locus is partially accessible in this “ex–T-bet” population with a history of T-bet expression. Furthermore, multicolor tissue imaging revealed that the ex–T-bet Tfh cells found in germinal centers express IFN-γ in situ. Finally, we found that IFN-γ–expressing Tfh cells are absent in T-bet–deficient mice, but fully present in mice with T-bet deletion at late stages of T cell differentiation. Together, our findings demonstrate that transient expression of T-bet epigenetically imprints the Ifng locus for cytokine production in this Th1-like Tfh cell subset.
Includes: Supplementary data
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2018) 215 (5): 1273–1285.
Published: 17 April 2018
Abstract
Tuberculosis remains one of the leading causes of mortality worldwide, and, despite its clinical significance, there are still significant gaps in our understanding of pathogenic and protective mechanisms triggered by Mycobacterium tuberculosis infection. Type I interferons (IFN) regulate a broad family of genes that either stimulate or inhibit immune function, having both host-protective and detrimental effects, and exhibit well-characterized antiviral activity. Transcriptional studies have uncovered a potential deleterious role for type I IFN in active tuberculosis. Since then, additional studies in human tuberculosis and experimental mouse models of M. tuberculosis infection support the concept that type I IFN promotes both bacterial expansion and disease pathogenesis. More recently, studies in a different setting have suggested a putative protective role for type I IFN. In this study, we discuss the mechanistic and contextual factors that determine the detrimental versus beneficial outcomes of type I IFN induction during M. tuberculosis infection, from human disease to experimental mouse models of tuberculosis.
Journal Articles
David G. Kugler, Francis A. Flomerfelt, Diego L. Costa, Karen Laky, Olena Kamenyeva, Paul R. Mittelstadt, Ronald E. Gress, Stephan P. Rosshart, Barbara Rehermann, Jonathan D. Ashwell, Alan Sher, Dragana Jankovic
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2016) 213 (13): 3041–3056.
Published: 14 November 2016
Abstract
Because antigen-stimulated naive T cells either die as effectors or enter the activated/memory pool, continuous egress of new T lymphocytes from thymus is essential for maintenance of peripheral immune homeostasis. Unexpectedly, we found that systemic infection with the protozoan Toxoplasma gondii triggers not only a transient increase in activated CD4 + Th1 cells but also a persistent decrease in the size of the naive CD4 + T lymphocyte pool. This immune defect is associated with decreased thymic output and parasite-induced destruction of the thymic epithelium, as well as disruption of the overall architecture of that primary lymphoid organ. Importantly, the resulting quantitative and qualitative deficiency in naive CD4 + T cells leads to an immunocompromised state that both promotes chronic toxoplasma infection and leads to decreased resistance to challenge with an unrelated pathogen. These findings reveal that systemic infectious agents, such as T. gondii , can induce long-term immune alterations associated with impaired thymic function. When accumulated during the lifetime of the host, such events, even when occurring at low magnitude, could be a contributing factor in immunological senescence.
Includes: Supplementary data
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2013) 210 (10): 1919–1927.
Published: 26 August 2013
Abstract
Synthetic glucocorticoids (GCs) are commonly used in the treatment of inflammatory diseases, but the role of endogenous GCs in the regulation of host-protective immune responses is poorly understood. Here we show that GCs are induced during acute Toxoplasma gondii infection and directly control the T cell response to the parasite. When infected with toxoplasma, mice that selectively lack GC receptor (GR) expression in T cells (GR lck-Cre ) rapidly succumb to infection despite displaying parasite burdens indistinguishable from control animals and unaltered levels of the innate cytokines IL-12 and IL-27. Mortality in the GR lck-Cre mice was associated with immunopathology and hyperactive Th1 cell function as revealed by enhanced IFN-γ and TNF production in vivo. Unexpectedly, these CD4 + T lymphocytes also overexpressed IL-10. Importantly, CD4 + T cell depletion in wild-type or GR lck-Cre mice led to ablation of the GC response to infection. Moreover, in toxoplasma-infected RAG −/− animals, adoptive transfer of CD4 + T lymphocytes was required for GC induction. These findings establish a novel IL-10–independent immunomodulatory circuit in which CD4 + T cells trigger a GC response that in turn dampens their own effector function. In the case of T. gondii infection, this self-regulatory pathway is critical for preventing collateral tissue damage and promoting host survival.
Journal Articles
Jacques Banchereau, Fern Cohn, Kayo Inaba, Bill Muller, Ira Mellman, Carl Nathan, Michel Nussenzweig, Anne O’Garra, Bob Seder, Gerold Schuler, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2011) 208 (12): 2343–2347.
Published: 21 November 2011
Abstract
As detailed in the Appreciation piece written by Carol Moberg , Ralph’s discovery and investigation of DCs constituted an enormous contribution to immunology. However, Ralph’s influence extended far beyond the strictly scientific. Below, some of Ralph’s closest colleagues and friends reflect on the long-lasting effects of his unwavering mentorship, enthusiasm, generosity, and friendship. Also in this issue is a Perspective, originally commissioned by Ralph and written by Robin Weiss and Peter Vogt . Ralph passed away before he could read this engaging piece, which celebrates the centennial of the publication in the JEM of the Nobel Prize-winning work of Peyton Rous. In addition to their Nobel Prizes, Ralph and Peyton Rous shared the distinctions of being long-time leaders of Rockefeller laboratories and editors of this journal.
Journal Articles
Svenja Steinfelder, John F. Andersen, Jennifer L. Cannons, Carl G. Feng, Manju Joshi, Dennis Dwyer, Pat Caspar, Pamela L. Schwartzberg, Alan Sher, Dragana Jankovic
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2009) 206 (8): 1681–1690.
Published: 27 July 2009
Abstract
Schistosoma mansoni eggs contain factors that trigger potent Th2 responses in vivo and condition mouse dendritic cells (DCs) to promote Th2 lymphocyte differentiation. Using an in vitro bystander polarization assay as the readout, we purified and identified the major Th2-inducing component from soluble egg extract (SEA) as the secreted T2 ribonuclease, omega-1. The Th2-promoting activity of omega-1 was found to be sensitive to ribonuclease inhibition and did not require MyD88/TRIF signaling in DCs. In common with unfractioned SEA, the purified native protein suppresses lipopolysaccharide-induced DC activation, but unlike SEA, it fails to trigger interleukin 4 production from basophils. Importantly, omega-1–exposed DCs displayed pronounced cytoskeletal changes and exhibited decreased antigen-dependent conjugate formation with CD4 + T cells. Based on this evidence, we hypothesize that S. mansoni omega-1 acts by limiting the interaction of DCs with CD4 + T lymphocytes, thereby lowering the strength of the activation signal delivered.
Includes: Supplementary data
Journal Articles
Andrea la Sala, Jianping He, Leopoldo Laricchia-Robbio, Stefania Gorini, Akiko Iwasaki, Michael Braun, George S. Yap, Alan Sher, Keiko Ozato, Brian Kelsall
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2009) 206 (7): 1635.
Published: 29 June 2009
Journal Articles
Andrea la Sala, Jianping He, Leopoldo Laricchia-Robbio, Stefania Gorini, Akiko Iwasaki, Michael Braun, George S. Yap, Alan Sher, Keiko Ozato, Brian Kelsall
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2009) 206 (6): 1227–1235.
Published: 01 June 2009
Abstract
Prior studies have demonstrated that cholera toxin (CT) and other cAMP-inducing factors inhibit interleukin (IL)-12 production from monocytes and dendritic cells (DCs). We show that CT inhibits Th1 responses in vivo in mice infected with Toxoplasma gondii. This correlated with low serum IL-12 levels and a selective reduction in the numbers of CD8α + conventional DCs (cDCs) in lymphoid organs. CT inhibited the function of interferon (IFN) regulatory factor (IRF) 8, a transcription factor known to positively regulate IL-12p35 and p40 gene expression, and the differentiation of CD8α + and plasmacytoid DCs (pDCs). Fluorescence recovery after photobleaching analysis showed that exposure to CT, forskolin, or dibutyryl (db) cAMP blocked LPS and IFN-γ–induced IRF8 binding to chromatin. Moreover, CT and dbcAMP inhibited the binding of IRF8 to the IFN-stimulated response element (ISRE)–like element in the mouse IL-12p40 promoter, likely by blocking the formation of ISRE-binding IRF1–IRF8 heterocomplexes. Furthermore, CT inhibited the differentiation of pDCs from fms-like tyrosine kinase 3 ligand–treated bone marrow cells in vitro. Therefore, because IRF8 is essential for IL-12 production and the differentiation of CD8α + cDCs and pDCs, these data suggest that CT and other Gs-protein agonists can affect IL-12 production and DC differentiation via a common mechanism involving IRF8.
Includes: Supplementary data
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2009) 206 (2): 399–410.
Published: 19 January 2009
Abstract
Toxoplasma gondii tachyzoites infect host cells by an active invasion process leading to the formation of a specialized compartment, the parasitophorous vacuole (PV). PVs resist fusion with host cell endosomes and lysosomes and are thus distinct from phagosomes. Because the parasite remains sequestered within the PV, it is unclear how T. gondii –derived antigens (Ag’s) access the major histocompatibility complex (MHC) class I pathway for presentation to CD8 + T cells. We demonstrate that recruitment of host endoplasmic reticulum (hER) to the PV in T. gondii –infected dendritic cells (DCs) directly correlates with cross-priming of CD8 + T cells. Furthermore, we document by immunoelectron microscopy the transfer of hER components into the PV, a process indicative of direct fusion between the two compartments. In strong contrast, no association between hER and phagosomes or Ag presentation activity was observed in DCs containing phagocytosed live or dead parasites. Importantly, cross-presentation of parasite-derived Ag in actively infected cells was blocked when hER retrotranslocation was inhibited, indicating that the hER serves as a conduit for the transport of Ag between the PV and host cytosol. Collectively, these findings demonstrate that pathogen-driven hER–PV interaction can serve as an important mechanism for Ag entry into the MHC class I pathway and CD8 + T cell cross-priming.
Includes: Supplementary data
Journal Articles
Wendy T. Watford, Bruce D. Hissong, Lydia R. Durant, Hidehiro Yamane, Linda M. Muul, Yuka Kanno, Cristina M. Tato, Haydeé L. Ramos, Alan E. Berger, Lisa Mielke, Marko Pesu, Benjamin Solomon, David M. Frucht, William E. Paul, Alan Sher, Dragana Jankovic, Philip N. Tsichlis, John J. O'Shea
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2008) 205 (12): 2803–2812.
Published: 10 November 2008
Abstract
Tpl2 (Tumor progression locus 2), also known as Cot/MAP3K8, is a hematopoietically expressed serine-threonine kinase. Tpl2 is known to have critical functions in innate immunity in regulating tumor necrosis factor–α, Toll-like receptor, and G protein–coupled receptor signaling; however, our understanding of its physiological role in T cells is limited. We investigated the potential roles of Tpl2 in T cells and found that it was induced by interleukin-12 in human and mouse T cells in a Stat4-dependent manner. Deficiency of Tpl2 was associated with impaired interferon (IFN)-γ production. Accordingly, Tpl2 −/− mice had impaired host defense against Toxoplasma gondii with reduced parasite clearance and decreased IFN-γ production. Furthermore, reconstitution of Rag2 −/− mice with Tpl2-deficient T cells followed by T. gondii infection recapitulated the IFN-γ defect seen in the Tpl2-deficient mice, confirming a T cell–intrinsic defect. CD4 + T cells isolated from Tpl2 −/− mice showed poor induction of T-bet and failure to up-regulate Stat4 protein, which is associated with impaired TCR-dependent extracellular signal-regulated kinase activation. These data underscore the role of Tpl2 as a regulator of T helper cell lineage decisions and demonstrate that Tpl2 has an important functional role in the regulation of Th1 responses.
Includes: Supplementary data
Journal Articles
Romina S. Goldszmid, Andre Bafica, Dragana Jankovic, Carl G. Feng, Pat Caspar, Robin Winkler-Pickett, Giorgio Trinchieri, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2007) 204 (11): 2591–2602.
Published: 08 October 2007
Abstract
To investigate if transporter associated with antigen processing (TAP)–1 is required for CD8 + T cell–mediated control of Toxoplasma gondii in vivo, we compared the resistance of TAP-1 −/− , CD8 −/− , and wild-type (WT) mice to infection with the parasite. Unexpectedly, TAP-1 −/− mice displayed greater susceptibility than CD8 −/− , β 2 -microglobulin −/− (β 2 m −/− ), or WT mice to infection with an avirulent parasite strain. The decreased resistance of the TAP-1 −/− mice correlated with a reduction in the frequency of activated (CD62L low CD44 hi ) and interferon (IFN)-γ–producing CD4 + T cells. Interestingly, infected TAP-1 −/− mice also showed reduced numbers of IFN-γ–producing natural killer (NK) cells relative to WT, CD8 −/− , or β 2 m −/− mice, and after NK cell depletion both CD8 −/− and WT mice succumbed to infection with the same kinetics as TAP-1 −/− animals and displayed impaired CD4 + T cell IFN-γ responses. Moreover, adoptive transfer of NK cells obtained from IFN-γ +/+ , but not IFN-γ −/− , animals restored the CD4 + T cell response of infected TAP-1 −/− mice to normal levels. These results reveal a role for TAP-1 in the induction of IFN-γ–producing NK cells and demonstrate that NK cell licensing can influence host resistance to infection through its effect on cytokine production in addition to its role in cytotoxicity.
Includes: Supplementary data
Journal Articles
Dragana Jankovic, Marika C. Kullberg, Carl G. Feng, Romina S. Goldszmid, Carmen M. Collazo, Mark Wilson, Thomas A. Wynn, Masahito Kamanaka, Richard A. Flavell, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2007) 204 (2): 273–283.
Published: 05 February 2007
Abstract
Although interferon γ (IFN-γ) secretion is essential for control of most intracellular pathogens, host survival often also depends on the expression of interleukin 10 (IL-10), a cytokine known to counteract IFN-γ effector functions. We analyzed the source of regulatory IL-10 in mice infected with the protozoan parasite Toxoplasma gondii . Unexpectedly, IFN-γ–secreting T-bet + Foxp3 − T helper type 1 (Th1) cells were found to be the major producers of IL-10 in these animals. Further analysis revealed that the same IL-10 + IFN-γ γ population displayed potent effector function against the parasite while, paradoxically, also inducing profound suppression of IL-12 production by antigen-presenting cells. Although at any given time point only a fraction of the cells appeared to simultaneously produce IL-10 and IFN-γ, IL-10 production could be stimulated in IL-10 − IFN-γ + cells by further activation in vitro. In addition, experiments with T. gondii– specific IL-10 + IFN-γ + CD4 clones revealed that although IFN-γ expression is imprinted and triggered with similar kinetics regardless of the state of Th1 cell activation, IL-10 secretion is induced more rapidly from recently activated than from resting cells. These findings indicate that IL-10 production by CD4 + T lymphocytes need not involve a distinct regulatory Th cell subset but can be generated in Th1 cells as part of the effector response to intracellular pathogens.
Includes: Supplementary data
Journal Articles
Marika C. Kullberg, Dragana Jankovic, Carl G. Feng, Sophie Hue, Peter L. Gorelick, Brent S. McKenzie, Daniel J. Cua, Fiona Powrie, Allen W. Cheever, Kevin J. Maloy, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2006) 203 (11): 2485–2494.
Published: 09 October 2006
Abstract
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract that is caused in part by a dysregulated immune response to the intestinal flora. The common interleukin (IL)-12/IL-23p40 subunit is thought to be critical for the pathogenesis of IBD. We have analyzed the role of IL-12 versus IL-23 in two models of Helicobacter hepaticus –triggered T cell–dependent colitis, one involving anti–IL-10R monoclonal antibody treatment of infected T cell–sufficient hosts, and the other involving CD4 + T cell transfer into infected Rag −/− recipients. Our data demonstrate that IL-23 and not IL-12 is essential for the development of maximal intestinal disease. Although IL-23 has been implicated in the differentiation of IL-17–producing CD4 + T cells that alone are sufficient to induce autoimmune tissue reactivity, our results instead support a model in which IL-23 drives both interferon γ and IL-17 responses that together synergize to trigger severe intestinal inflammation.
Journal Articles
Jennifer L. Cannons, Li J. Yu, Dragana Jankovic, Shane Crotty, Reiko Horai, Martha Kirby, Stacie Anderson, Allen W. Cheever, Alan Sher, Pamela L. Schwartzberg
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2006) 203 (6): 1551–1565.
Published: 05 June 2006
Abstract
X-linked lymphoproliferative disease is caused by mutations affecting SH2D1A / SAP , an adaptor that recruits Fyn to signal lymphocyte activation molecule (SLAM)-related receptors. After infection, SLAM-associated protein (SAP) −/− mice show increased T cell activation and impaired humoral responses. Although SAP −/− mice can respond to T-independent immunization, we find impaired primary and secondary T-dependent responses, with defective B cell proliferation, germinal center formation, and antibody production. Nonetheless, transfer of wild-type but not SAP-deficient CD4 cells rescued humoral responses in reconstituted recombination activating gene 2 −/− and SAP −/− mice. To investigate these T cell defects, we examined CD4 cell function in vitro and in vivo. Although SAP-deficient CD4 cells have impaired T cell receptor–mediated T helper (Th)2 cytokine production in vitro, we demonstrate that the humoral defects can be uncoupled from cytokine expression defects in vivo. Instead, SAP-deficient T cells exhibit decreased and delayed inducible costimulator (ICOS) induction and heightened CD40L expression. Notably, in contrast to Th2 cytokine defects, humoral responses, ICOS expression, and CD40L down-regulation were rescued by retroviral reconstitution with SAP-R78A, a SAP mutant that impairs Fyn binding. We further demonstrate a role for SLAM/SAP signaling in the regulation of early surface CD40L expression. Thus, SAP affects expression of key molecules required for T–B cell collaboration by mechanisms that are distinct from its role in cytokine regulation.
Includes: Supplementary data
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2005) 202 (12): 1715–1724.
Published: 19 December 2005
Abstract
To investigate the role of Toll-like receptor (TLR)9 in the immune response to mycobacteria as well as its cooperation with TLR2, a receptor known to be triggered by several major mycobacterial ligands, we analyzed the resistance of TLR9 − / − as well as TLR2/9 double knockout mice to aerosol infection with Mycobacterium tuberculosis . Infected TLR9 − / − but not TLR2 − / − mice displayed defective mycobacteria-induced interleukin (IL)-12p40 and interferon (IFN)- γ responses in vivo, but in common with TLR2 − / − animals, the TLR9 − / − mice exhibited only minor reductions in acute resistance to low dose pathogen challenge. When compared with either of the single TLR-deficient animals, TLR2/9 − / − mice displayed markedly enhanced susceptibility to infection in association with combined defects in proinflammatory cytokine production in vitro, IFN- γ recall responses ex vivo, and altered pulmonary pathology. Cooperation between TLR9 and TLR2 was also evident at the level of the in vitro response to live M. tuberculosis , where dendritic cells and macrophages from TLR2/9 − / − mice exhibited a greater defect in IL-12 response than the equivalent cell populations from single TLR9-deficient animals. These findings reveal a previously unappreciated role for TLR9 in the host response to M. tuberculosis and illustrate TLR collaboration in host resistance to a major human pathogen.
Includes: Supplementary data
Journal Articles
Makoto Arita, Francesca Bianchini, Julio Aliberti, Alan Sher, Nan Chiang, Song Hong, Rong Yang, Nicos A. Petasis, Charles N. Serhan
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2005) 201 (5): 713–722.
Published: 07 March 2005
Abstract
The essential fatty acid eicosapentaenoic acid (EPA) present in fish oils displays beneficial effects in a range of human disorders associated with inflammation including cardiovascular disease. Resolvin E1 (RvE1), a new bioactive oxygenated product of EPA, was identified in human plasma and prepared by total organic synthesis. Results of bioaction and physical matching studies indicate that the complete structure of RvE1 is 5S,12R,18R-trihydroxy-6Z,8E,10E,14Z,16E-EPA. At nanomolar levels, RvE1 dramatically reduced dermal inflammation, peritonitis, dendritic cell (DC) migration, and interleukin (IL) 12 production. We screened receptors and identified one, denoted earlier as ChemR23, that mediates RvE1 signal to attenuate nuclear factor–κB. Specific binding of RvE1 to this receptor was confirmed using synthetic [ 3 H]-labeled RvE1. Treatment of DCs with small interference RNA specific for ChemR23 sharply reduced RvE1 regulation of IL-12. These results demonstrate novel counterregulatory responses in inflammation initiated via RvE1 receptor activation that provide the first evidence for EPA-derived potent endogenous agonists of antiinflammation.
Includes: Supplementary data
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2004) 199 (4): 515–523.
Published: 17 February 2004
Abstract
Lipoxin A 4 (LXA 4 ) is a potent endogenous lipoxygenase-derived eicosanoid with antiinflammatory and proresolving properties. Supraphysiological levels of LXA 4 are generated during infection by Toxoplasma gondii , which in turn reduces interleukin (IL) 12 production by dendritic cells, thus dampening Th1-type cell-mediated immune responses and host immunopathology. In the present work, we sought evidence for the structural basis of T. gondii 's ability to activate LXA 4 biosynthesis. Proteomic analysis of T. gondii extract (soluble tachyzoite antigen [STAg]), which preserves the immunosuppressive and antiinflammatory activity of the parasite, yielded several peptide matches to known plant lipoxygenases. Hence, we incubated STAg itself with arachidonic acid and found using LC-UV-MS-MS–based lipidomics that STAg produced both 15-HETE and 5,15-diHETE, indicating that T. gondii carries 15-lipoxygenase activity. In addition, T. gondii tachyzoites (the rapidly multiplying and invasive stage of the parasite) generated LXA 4 when provided with arachidonic acid. Local administration of a plant (soybean) lipoxygenase itself reduced neutrophilic infiltration in murine peritonitis, demonstrating that 15-lipoxygenase possesses antiinflammatory properties. Administration of plant 15-lipoxygenase generated endogenous LXA 4 and mimicked the suppression of IL-12 production by splenic dendritic cells observed after T. gondii infection or STAg administration. Together, these results indicate that 15-lipoxygenase expressed by a pathogen as well as exogenously administered 15-lipoxygenase can interact with host biosynthetic circuits for endogenous “stop signals” that divert the host immune response and limit acute inflammation.
Journal Articles
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2002) 196 (9): 1253–1262.
Published: 04 November 2002
Abstract
The production of interleukin (IL)-12 is critical for the development of interferon (IFN)-γ–dependent resistance to Toxoplasma gondii . Nevertheless, when this response is dysregulated, such as occurs in the absence of IL-10, the uncontrolled inflammation that results can have lethal consequences for the host. Recently, we demonstrated that lipoxin (LX)A 4 , an eicosanoid mediator that depends on 5-lipoxygenase (LO) for its biosynthesis, exerts a regulatory role on dendritic cell IL-12 production triggered artificially by a T. gondii extract. We now formally establish the physiological relevance of this pathway in the systemic control of IL-12 production induced by live T. gondii infection and demonstrate its function to be distinct from that of IL-10. Thus, T. gondii –exposed wild-type, but not 5-LO–deficient animals, produced high levels of serum LXA 4 beginning at the onset of chronic infection. Moreover, 5-LO −/− , in contrast to wild-type mice, succumbed during the same period displaying a marked encephalitis. The increased mortality of the 5-LO −/− animals was also associated with significant elevations of IL-12 and IFN-γ and was completely prevented by the administration of a stable LXA 4 analogue. Together, these findings demonstrate a new pathway involving the induction of host LXs for the in vivo regulation of proinflammatory responses during microbial infection.
Journal Articles
Marika C. Kullberg, Dragana Jankovic, Peter L. Gorelick, Patricia Caspar, John J. Letterio, Allen W. Cheever, Alan Sher
Journal:
Journal of Experimental Medicine
Journal of Experimental Medicine (2002) 196 (4): 505–515.
Published: 19 August 2002
Abstract
We have previously demonstrated that interleukin (IL)-10–deficient (IL-10 knockout [KO]) but not wild-type (WT) mice develop colitis after infection with Helicobacter hepaticus . Here, we show that infected recombination activating gene (RAG) KO mice develop intestinal inflammation after reconstitution with CD4 + T cells from IL-10 KO animals and that the cotransfer of CD4 + T cells from H. hepaticus –infected but not uninfected WT mice prevents this colitis. The disease-protective WT CD4 + cells are contained within the CD45RB low fraction and unexpectedly were found in both the CD25 + and the CD25 − subpopulations of these cells, their frequency being higher in the latter. The mechanism by which CD25 + and CD25 − CD45RB low CD4 + cells block colitis involves IL-10 and not transforming growth factor (TGF)-β, as treatment with anti–IL-10R but not anti–TGF-β monoclonal antibody abrogated their protective effect. In vitro, CD45RB low CD4 + cells from infected WT mice were shown to produce IL-10 and suppress interferon-γ production by IL-10 KO CD4 + cells in an H. hepaticus antigen–specific manner. Together, our data support the concept that H. hepaticus infection results in the induction in WT mice of regulatory T cells that prevent bacteria-induced colitis. The induction of such cells in response to gut flora may be a mechanism protecting normal individuals against inflammatory bowel disease.