Heat shock protein 70 is a positive regulator of airway inflammation and goblet cell hyperplasia in a mouse model of allergic airway inflammation.

Heat shock proteins (Hsps) are highly conserved molecular chaperones that are ubiquitously expressed in all species to aid the solubilization of misfolded proteins, protein degradation, and transport. Elevated levels of Hsp70 have been found in the sputum, serum, and bronchoalveolar lavage (BAL) fluid of asthma patients and are known to correlate with disease severity. However, the function of Hsp70 in allergic airway inflammation has remained largely unknown. This study aimed to determine the role of Hsp70 in airway inflammation and remodeling using a mouse model of allergic airway inflammation. WT and Hsp70 double-knockout (Hsp70.1/.3-/-) mice were sensitized and challenged intratracheally with Schistosoma mansoni soluble egg antigens (SEAs) to induce robust Th2 responses and airway inflammation in the lungs. The lack of Hsp70 resulted in a significant reduction in airway inflammation, goblet cell hyperplasia, and Th2 cytokine production, including IL-4, IL-5, and IL-13. An analysis of the BAL fluid suggested that Hsp70 is critically required for eosinophilic infiltration, collagen accumulation, and Th2 cytokine production in allergic airways. Furthermore, our bone marrow (BM) transfer studies show that SEA-induced airway inflammation, goblet cell hyperplasia, and Th2 cytokine production were attenuated in WT mice that were reconstituted with Hsp70-deficient BM, but these effects were not attenuated in Hsp70-deficient mice that were reconstituted with WT BM. Together, these studies identify a pathogenic role for Hsp70 in hematopoietic cells during allergic airway inflammation; this illustrates the potential utility of targeting Hsp70 to alleviate allergen-induced Th2 cytokines, goblet cell hyperplasia, and airway inflammation.

Unique functions of the type II interleukin 4 receptor identified in mice lacking the interleukin 13 receptor alpha1 chain.

The interleukin 4 receptor (IL-4R) is a central mediator of T helper type 2 (T(H)2)-mediated disease and associates with either the common gamma-chain to form the type I IL-4R or with the IL-13R alpha1 chain (IL-13Ralpha1) to form the type II IL-4R. Here we used Il13ra1-/- mice to characterize the distinct functions of type I and type II IL-4 receptors in vivo. In contrast to Il4ra-/- mice, which have weak T(H)2 responses, Il13ra1-/- mice had exacerbated T(H)2 responses. Il13ra1-/- mice showed much less mortality after infection with Schistosoma mansoni and much more susceptibility to Nippostrongylus brasiliensis. IL-13Ralpha1 was essential for allergen-induced airway hyperreactivity and mucus hypersecretion but not for fibroblast or alternative macrophage activation. Thus, type I and II IL-4 receptors exert distinct effects on immune responses.

Enhanced protection from fibrosis and inflammation in the combined absence of IL-13 and IFN-γ.

Persistent or dysregulated IL-13 responses are key drivers of fibrosis in multiple organ systems, and this identifies this cytokine as an important therapeutic target. Nevertheless, the mechanisms by which IL-13 blockade leads to the amelioration of fibrosis remain unclear. Because IFN-γ exhibits potent anti-fibrotic activity, and IL-4Rα signalling antagonizes IFN-γ effector function, compensatory increases in IFN-γ activity following IL-13/IL-4Rα blockade might contribute to the reduction in fibrosis. To investigate the role of IFN-γ, we developed novel IL-13(-/-) /IFN-γ(-/-) double cytokine-deficient mice and examined disease progression in models of type 2-driven fibrosis. As predicted, we showed that fibrosis in the lung and liver are both highly dependent on IL-13. We also observed increased IFN-γ production and inflammatory activity in the tissues of IL-13-deficient mice. Surprisingly, however, an even greater reduction in fibrosis was observed in IL-13/IFN-γ double deficient mice, most notably in the livers of mice chronically infected with Schistosoma mansoni. The increased protection was associated with marked decreases in Tgfb1, Mmp12, and Timp1 mRNA expression in the tissues; reduced inflammation; and decreased expression of important pro-inflammatory mediators such as TNF-α. Experiments conducted with neutralizing monoclonal antibodies to IL-13 and IFN-γ validated the findings with the genetically deficient mice. Together, these studies demonstrate that the reduction in fibrosis observed when IL-13 signalling is suppressed is not dependent on increased IFN-γ activity. Instead, by reducing compensatory increases in type 1-associated inflammation, therapeutic strategies that block IFN-γ and IL-13 activity simultaneously can confer greater protection from progressive fibrosis than IL-13 blockade alone. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Induction and activation of latent transforming growth factor-ß1 are carried out by two distinct domains of pregnancy-specific glycoprotein 1 (PSG1).

Pregnancy-specific glycoproteins (PSGs) are a family of Ig-like proteins secreted by specialized placental cells. The PSG1 structure is composed of a single Ig variable region-like N-terminal domain and three Ig constant region-like domains termed A1, A2, and B2. Members of the human and murine PSG family have been shown to induce anti-inflammatory cytokines from monocytes and macrophages and to stimulate angiogenesis. We recently showed that recombinant forms of PSG1 (PSG1-Fc and PSG1-His) and PSG1 purified from the serum of pregnant women are associated with the immunoregulatory cytokine TGF-ß1 and activated latent TGF-ß1. Here, we sought to examine the requirement of specific PSG1 domains in the activation of latent TGF-ß1. Plasmon surface resonance studies showed that PSG1 directly bound to the small latent complex and to the latency-associated peptide of TGF-ß1 and that this binding was mediated through the B2 domain. Furthermore, the B2 domain alone was sufficient for activating the small latent complex. In separate experiments, we found that the PSG1-mediated induction of TGF-ß1 secretion in macrophages was dependent on the N-terminal domain. Mutagenesis analysis revealed that four amino acids (LYHY) of the CC' loop of the N-terminal domain were required for induction of latent TGF-ß1 secretion. Together, our results show that two distinct domains of PSG1 are involved in the regulation of TGF-ß1 and provide a mechanistic framework for how PSGs modulate the immunoregulatory environment at the maternal-fetal interface for successful pregnancy outcome.

RGS16 attenuates pulmonary Th2/Th17 inflammatory responses.

The regulators of G protein signaling (RGS) protein superfamily negatively controls G protein-coupled receptor signal transduction pathways. RGS16 is enriched in activated/effector T lymphocytes. In this paper, we show that RGS16 constrains pulmonary inflammation by regulating chemokine-induced T cell trafficking in response to challenge with Schistosoma mansoni. Naive Rgs16(-/-) mice were "primed" for inflammation by accumulation of CCR10(+) T cells in the lung. Upon pathogen exposure, these mice developed more robust granulomatous lung fibrosis than wild-type counterparts. Distinct Th2 or putative Th17 subsets expressing CCR4 or CCR10 accumulated more rapidly in Rgs16(-/-) lungs following challenge and produced proinflammatory cytokines IL-13 and IL-17B. CCR4(+)Rgs16(-/-) Th2 cells migrated excessively to CCL17 and localized aberrantly in challenged lungs. T lymphocytes were partially excluded from lung granulomas in Rgs16(-/-) mice, instead forming peribronchial/perivascular aggregates. Thus, RGS16-mediated confinement of T cells to Schistosome granulomas mitigates widespread cytokine-mediated pulmonary inflammation.

Accelerated and progressive and lethal liver fibrosis in mice that lack interleukin (IL)-10, IL-12p40, and IL-13Rα2.

BACKGROUND & AIMS: Progressive fibrosis contributes to the morbidity of several chronic diseases; it typically develops slowly, so the mechanisms that control its progression and resolution have been difficult to model. The proteins interleukin (IL)-10, IL-12p40, and IL-13Rα2 regulate hepatic fibrosis following infection with the helminth parasite Schistosoma mansoni. We examined whether these mediators interact to slow the progression of hepatic fibrosis in mice with schistosomiasis. METHODS: IL-10(-/-), IL-12/23(p40)(-/-), and IL-13Rα2(-/-) mice were crossed to generate triple knockout (TKO) mice. We studied these mice to determine whether the simultaneous deletion of these 3 negative regulators of the immune response accelerated mortality from liver fibrosis following infection with S mansoni. RESULTS: Induction of inflammation by S mansoni, liver fibrosis, and mortality increased greatly in TKO mice compared with wild-type mice; 100% of the TKO mice died by 10 weeks after infection. Morbidity and mortality were associated with the development of portal hypertension, hepatosplenomegaly, gastrointestinal bleeding, ascites, thrombocytopenia, esophageal and gastric varices, anemia, and increased levels of liver enzymes, all features of advanced liver disease. IL-10, IL-12p40, and IL-13Rα2 reduced the production and activity of the profibrotic cytokine IL-13. A neutralizing antibody against IL-13 reduced the morbidity and mortality of the TKO mice following S mansoni infection. CONCLUSIONS: IL-10, IL-12p40, and IL-13Rα2 act cooperatively to suppress liver fibrosis in mice following infection with S mansoni. This model rapidly reproduces many of the complications observed in patients with advanced cirrhosis, so it might be used to evaluate the efficacy of antifibrotic reagents being developed for schistosomiasis or other fibrotic diseases associated with a T-helper 2 cell-mediated immune response.

Colitis and intestinal inflammation in IL10-/- mice results from IL-13Rα2-mediated attenuation of IL-13 activity.

BACKGROUND & AIMS: The cytokine interleukin (IL)-10 is required to maintain immune homeostasis in the gastrointestinal tract. IL-10 null mice spontaneously develop colitis or are more susceptible to induction of colitis by infections, drugs, and autoimmune reactions. IL-13 regulates inflammatory conditions; its activity might be compromised by the IL-13 decoy receptor (IL-13Rα2). METHODS: We examined the roles of IL-13 and IL-13Rα2 in intestinal inflammation in mice. To study the function of IL-13Rα2, il10(-/-) mice were crossed with il13rα2(-/-) to generate il10(-/-)il13rα2(-/-) double knockout (dKO) mice. Colitis was induced with the gastrointestinal toxin piroxicam or Trichuris muris infection. RESULTS: Induction of colitis by interferon (IFN)-γ or IL-17 in IL-10 null mice requires IL-13Rα2. Following exposure of il10(-/-) mice to piroxicam or infection with T muris, production of IL-13Rα2 increased, resulting in decreased IL-13 bioactivity and increased inflammation in response to IFN-γ or IL-17A. In contrast to il10(-/-) mice, dKO mice were resistant to piroxicam-induced colitis; they also developed less severe colitis during chronic infection with T muris infection. In both models, resistance to IFN-γ and IL-17-mediated intestinal inflammation was associated with increased IL-13 activity. Susceptibility to colitis was restored when the dKO mice were injected with monoclonal antibodies against IL-13, confirming its protective role. CONCLUSIONS: Colitis and intestinal inflammation in IL10(-/-) mice results from IL-13Rα2-mediated attenuation of IL-13 activity. In the absence of IL-13Rα2, IL-13 suppresses proinflammatory Th1 and Th17 responses. Reagents that block the IL-13 decoy receptor IL-13Rα2 might be developed for inflammatory bowel disease associated with increased levels of IFN-γ and IL-17.

Matrix metalloproteinase 12-deficiency augments extracellular matrix degrading metalloproteinases and attenuates IL-13-dependent fibrosis.

Infection with the parasitic helminth Schistosoma mansoni causes significant liver fibrosis and extracellular matrix (ECM) remodeling. Matrix metalloproteinases (MMP) are important regulators of the ECM by regulating cellular inflammation, extracellular matrix deposition, and tissue reorganization. MMP12 is a macrophage-secreted elastase that is highly induced in the liver and lung in response to S. mansoni eggs, confirmed by both DNA microarray and real-time PCR analysis. However, the function of MMP12 in chronic helminth-induced inflammation and fibrosis is unclear. In this study, we reveal that MMP12 acts as a potent inducer of inflammation and fibrosis after infection with the helminth parasite S. mansoni. Surprisingly, the reduction in liver and lung fibrosis in MMP12-deficient mice was not associated with significant changes in cytokine, chemokine, TGF-beta1, or tissue inhibitors of matrix metalloproteinase expression. Instead, we observed marked increases in MMP2 and MMP13 expression, suggesting that Mmp12 was promoting fibrosis by limiting the expression of specific ECM-degrading MMPs. Interestingly, like MMP12, MMP13 expression was highly dependent on IL-13 and type II-IL-4 receptor signaling. However, in contrast to MMP12, expression of MMP13 was significantly suppressed by the endogenous IL-13 decoy receptor, IL-13Ralpha2. In the absence of MMP12, expression of IL-13Ralpha2 was significantly reduced, providing a possible explanation for the increased IL-13-driven MMP13 activity and reduced fibrosis. As such, these data suggest important counter-regulatory roles between MMP12 and ECM-degrading enzymes like MMP2, MMP9, and MMP13 in Th2 cytokine-driven fibrosis.

Mapping mouse IL-13 binding regions using structure modeling, molecular docking, and high-density peptide microarray analysis.

Interleukin-13 is a Th2-associated cytokine responsible for many pathological responses in allergic asthma including mucus production, inflammation, and extracellular matrix remodeling. In addition, IL-13 is required for immunity to many helminth infections. IL-13 signals via the type-II IL-4 receptor, a heterodimeric receptor of IL-13Rα1 and IL-4Rα, which is also used by IL-4. IL-13 also binds to IL-13Rα2, but with much higher affinity than the type-II IL-4 receptor. Binding of IL-13 to IL-13Rα2 has been shown to attenuate IL-13 signaling through the type-II IL-4 receptor. However, molecular determinants that dictate the specificity and affinity of mouse IL-13 for the different receptors are largely unknown. Here, we used high-density overlapping peptide arrays, structural modeling, and molecular docking methods to map IL-13 binding sequences on its receptors. Predicted binding sequences on mouse IL-13Rα1 and IL-13Rα2 were in agreement with the reported human IL-13 receptor complex structures and site-directed mutational analysis. Novel structural differences were identified between IL-13 receptors, particularly at the IL-13 binding interface. Notably, additional binding sites were observed for IL-13 on IL-13Rα2. In addition, the identification of peptide sequences that are unique to IL-13Rα1 allowed us to generate a monoclonal antibody that selectively binds IL-13Rα1. Thus, high-density peptide arrays combined with molecular docking studies provide a novel, rapid, and reliable method to map cytokine-receptor interactions that may be used to generate signaling and decoy receptor-specific antagonists.

Arginase-1-expressing macrophages suppress Th2 cytokine-driven inflammation and fibrosis.

Macrophage-specific expression of Arginase-1 is commonly believed to promote inflammation, fibrosis, and wound healing by enhancing L-proline, polyamine, and Th2 cytokine production. Here, however, we show that macrophage-specific Arg1 functions as an inhibitor of inflammation and fibrosis following infection with the Th2-inducing pathogen Schistosoma mansoni. Although susceptibility to infection was not affected by the conditional deletion of Arg1 in macrophages, Arg1(-/flox);LysMcre mice died at an accelerated rate. The mortality was not due to acute Th1/NOS2-mediated hepatotoxicity or endotoxemia. Instead, granulomatous inflammation, liver fibrosis, and portal hypertension increased in infected Arg1(-/flox);LysMcre mice. Similar findings were obtained with Arg1(flox/flox);Tie2cre mice, which delete Arg1 in all macrophage populations. Production of Th2 cytokines increased in the infected Arg1(-/flox);LysMcre mice, and unlike alternatively activated wild-type macrophages, Arg1(-/flox);LysMcre macrophages failed to inhibit T cell proliferation in vitro, providing an underlying mechanism for the exacerbated Th2 pathology. The suppressive activity of Arg1-expressing macrophages was independent of IL-10 and TGF-beta1. However, when exogenous L-arginine was provided, T cell proliferation was restored, suggesting that Arg1-expressing macrophages deplete arginine, which is required to sustain CD4(+) T cell responses. These data identify Arg1 as the essential suppressive mediator of alternatively activated macrophages (AAM) and demonstrate that Arg1-expressing macrophages function as suppressors rather than inducers of Th2-dependent inflammation and fibrosis.

Retnla (relmalpha/fizz1) suppresses helminth-induced Th2-type immunity.

Retnla (Resistin-like molecule alpha/FIZZ1) is induced during Th2 cytokine immune responses. However, the role of Retnla in Th2-type immunity is unknown. Here, using Retnla(-/-) mice and three distinct helminth models, we show that Retnla functions as a negative regulator of Th2 responses. Pulmonary granuloma formation induced by the eggs of the helminth parasite Schistosoma mansoni is dependent on IL-4 and IL-13 and associated with marked increases in Retnla expression. We found that both primary and secondary pulmonary granuloma formation were exacerbated in the absence of Retlna. The number of granuloma-associated eosinophils and serum IgE titers were also enhanced. Moreover, when chronically infected with S. mansoni cercariae, Retnla(-/-) mice displayed significant increases in granulomatous inflammation in the liver and the development of fibrosis and progression to hepatosplenic disease was markedly augmented. Finally, Retnla(-/-) mice infected with the gastrointestinal (GI) parasite Nippostrongylus brasiliensis had intensified lung pathology to migrating larvae, reduced fecundity, and accelerated expulsion of adult worms from the intestine, suggesting Th2 immunity was enhanced. When their immune responses were compared, helminth infected Retnla(-/-) mice developed stronger Th2 responses, which could be reversed by exogenous rRelmalpha treatment. Studies with several cytokine knockout mice showed that expression of Retnla was dependent on IL-4 and IL-13 and inhibited by IFN-gamma, while tissue localization and cell isolation experiments indicated that eosinophils and epithelial cells were the primary producers of Retnla in the liver and lung, respectively. Thus, the Th2-inducible gene Retnla suppresses resistance to GI nematode infection, pulmonary granulomatous inflammation, and fibrosis by negatively regulating Th2-dependent responses.

Schistosomiasis-induced experimental pulmonary hypertension: role of interleukin-13 signaling.

The mechanisms underlying schistosomiasis-induced pulmonary hypertension (PH), one of the most common causes of PH worldwide, remain unclear. We sought to determine whether Schistosoma mansoni causes experimental PH associated with pulmonary vascular remodeling in an interleukin (IL)-13-dependent manner. IL-13Ralpha1 is the canonical IL-13 signaling receptor, whereas IL-13Ralpha2 is a competitive nonsignaling decoy receptor. Wild-type, IL-13Ralpha1(-/-), and IL-13Ralpha2(-/-) C57BL/6J mice were percutaneously infected with S. mansoni cercariae, followed by i.v. injection of eggs. We assessed PH with right ventricular catheterization, histological evaluation of pulmonary vascular remodeling, and detection of IL-13 and transforming growth factor-beta signaling. Infected mice developed pulmonary peri-egg granulomas and arterial remodeling involving predominantly the vascular media. In addition, gain-of-function IL-13Ralpha2(-/-) mice had exacerbated vascular remodeling and PH. Mice with loss of IL-13Ralpha1 function did not develop PH and had reduced pulmonary vascular remodeling. Moreover, the expression of resistin-like molecule-alpha, a target of IL-13 signaling, was increased in infected wild-type and IL-13Ralpha2(-/-) but not IL-13Ralpha1(-/-) mice. Phosphorylated Smad2/3, a target of transforming growth factor-beta signaling, was increased in both infected mice and humans with the disease. Our data indicate that experimental schistosomiasis causes PH and potentially relies on up-regulated IL-13 signaling.

Regulation of helminth-induced Th2 responses by thymic stromal lymphopoietin.

Thymic stromal lymphopoietin was recently identified as a master switch for the development of allergen-driven Th2 responses. However, the role of thymic stromal lymphopoietin (TSLP) in the development of helminth-induced Th2 responses is unclear. Here, using TSLPR(-/-) mice, we show that while TSLPR signaling participates in the development of Schistosoma mansoni egg-induced CD4(+) Th2 responses, it plays only a transient role in the development of Th2-dependent pathology in the lung, liver, and intestine. Studies conducted in a pulmonary granuloma model showed that while a reduction in IL-4/IL-13-dependent granulomatous inflammation and tissue eosinophilia was observed in TSLPR(-/-) mice undergoing a primary response, lesion formation was not affected during a secondary granulomatous response, even though IL-5 and IL-13 were modestly reduced in the knockout mice. To evaluate the importance of TSLPR signaling in the development of a chronic Th2-dependent response, TSLPR(-/-) mice were also infected with S. mansoni cercariae. Here, the only significant difference noted in TSLPR(-/-) mice was a modest decrease in liver fibrosis in acutely infected animals. The transient decrease in fibrosis was associated with increased production of the antifibrotic cytokine IFN-gamma and decreased production of the profibrotic cytokine IL-13. Although the altered cytokine response persisted in chronically infected TSLPR(-/-) mice, it failed to reduce granuloma formation or fibrosis, confirming that TSLPR signaling plays a limited role in the development of chronic Th2-dependent pathology. Collectively, these findings suggest that while TSLPR signaling serves a key role in allergen-driven Th2 responses, it exerts minor regulatory activity during this chronic helminth infection.

IL-13Ralpha2 and IL-10 coordinately suppress airway inflammation, airway-hyperreactivity, and fibrosis in mice.

Development of persistent Th2 responses in asthma and chronic helminth infections are a major health concern. IL-10 has been identified as a critical regulator of Th2 immunity, but mechanisms for controlling Th2 effector function remain unclear. IL-10 also has paradoxical effects on Th2-associated pathology, with IL-10 deficiency resulting in increased Th2-driven inflammation but also reduced airway hyperreactivity (AHR), mucus hypersecretion, and fibrosis. We demonstrate that increased IL-13 receptor alpha 2 (IL-13Ralpha2) expression is responsible for the reduced AHR, mucus production, and fibrosis in BALB/c IL-10(-/-) mice. Using models of allergic asthma and chronic helminth infection, we demonstrate that IL-10 and IL-13Ralpha2 coordinately suppress Th2-mediated inflammation and pathology, respectively. Although IL-10 was identified as the dominant antiinflammatory mediator, studies with double IL-10/IL-13Ralpha2-deficient mice illustrate an indispensable role for IL-13Ralpha2 in the suppression of AHR, mucus production, and fibrosis. Thus, IL-10 and IL-13Ralpha2 are both required to control chronic Th2-driven pathological responses.

Programmed genome editing of the omega-1 ribonuclease of the blood fluke, Schistosoma mansoni.

CRISPR/Cas9-based genome editing has yet to be reported in species of the Platyhelminthes. We tested this approach by targeting omega-1 (ω1) of Schistosoma mansoni as proof of principle. This secreted ribonuclease is crucial for Th2 polarization and granuloma formation. Schistosome eggs were exposed to Cas9 complexed with guide RNA complementary to ω1 by electroporation or by transduction with lentiviral particles. Some eggs were also transfected with a single stranded donor template. Sequences of amplicons from gene-edited parasites exhibited Cas9-catalyzed mutations including homology directed repaired alleles, and other analyses revealed depletion of ω1 transcripts and the ribonuclease. Gene-edited eggs failed to polarize Th2 cytokine responses in macrophage/T-cell co-cultures, while the volume of pulmonary granulomas surrounding ω1-mutated eggs following tail-vein injection into mice was vastly reduced. Knock-out of ω1 and the diminished levels of these cytokines following exposure showcase the novel application of programmed gene editing for functional genomics in schistosomes.

The NIH-NIAID Schistosomiasis Resource Center at the Biomedical Research Institute: Molecular Redux.

Schistosomiasis remains a health burden in many parts of the world. The complex life cycle of Schistosoma parasites and the economic and societal conditions present in endemic areas make the prospect of eradication unlikely in the foreseeable future. Continued and vigorous research efforts must therefore be directed at this disease, particularly since only a single World Health Organization (WHO)-approved drug is available for treatment. The National Institutes of Health (NIH)-National Institute of Allergy and Infectious Diseases (NIAID) Schistosomiasis Resource Center (SRC) at the Biomedical Research Institute provides investigators with the critical raw materials needed to carry out this important research. The SRC makes available, free of charge (including international shipping costs), not only infected host organisms but also a wide array of molecular reagents derived from all life stages of each of the three main human schistosome parasites. As the field of schistosomiasis research rapidly advances, it is likely to become increasingly reliant on omics, transgenics, epigenetics, and microbiome-related research approaches. The SRC has and will continue to monitor and contribute to advances in the field in order to support these research efforts with an expanding array of molecular reagents. In addition to providing investigators with source materials, the SRC has expanded its educational mission by offering a molecular techniques training course and has recently organized an international schistosomiasis-focused meeting. This review provides an overview of the materials and services that are available at the SRC for schistosomiasis researchers, with a focus on updates that have occurred since the original overview in 2008.

T cell-specific deletion of the inositol phosphatase SHIP reveals its role in regulating Th1/Th2 and cytotoxic responses.

The 5'-phosphoinositol phosphatase SHIP negatively regulates signaling pathways triggered by antigen, cytokine and Fc receptors in both lymphocytes and myeloid cells. Mice with germ-line (null) deletion of SHIP develop a myeloproliferative-like syndrome that causes early lethality. Lymphocyte anomalies have been observed in SHIP-null mice, but it is unclear whether they are due to an intrinsic requirement of SHIP in these cells or a consequence of the severe myeloid pathology. To precisely address the function of SHIP in T cells, we have generated mice with T cell-specific deletion of SHIP. In the absence of SHIP, we found no differences in thymic selection or in the activation state and numbers of regulatory T cells in the periphery. In contrast, SHIP-deficient T cells do not skew efficiently to Th2 in vitro. Mice with T cell-specific deletion of SHIP show poor antibody responses on Alum/NP-CGG immunization and diminished Th2 cytokine production when challenged with Schistosoma mansoni eggs. The failure to skew to Th2 responses may be the consequence of increased basal levels of the Th1-associated transcriptional factor T-bet, resulting from enhanced sensitivity to cytokine-mediated T-bet induction. SHIP-deficient CD8(+) cells show enhanced cytotoxic responses, consistent with elevated T-bet levels in these cells. Overall our experiments indicate that in T cells SHIP negatively regulates cytokine-mediated activation in a way that allows effective Th2 responses and limits T cell cytotoxicity.

Immunopathology of schistosomiasis.

Waterborne parasitic diseases plague tropical regions of the world with the development of water resources often increasing transmission. Skin-penetrating cercariae (infectious stages of schistosome parasites) mature within their mammalian host, form sexual pairs and produce several hundred eggs per day. Many eggs are swept within the circulation and in the case of Schistosoma mansoni and S. japonicum, become lodged within hepatic sinusoids, invoking a fibrotic granulomatous response. Animal studies have identified a moderate type 1 helper (Th1) response to parasite antigens; however, a robust Th2 response to egg-derived antigens dominates and propagates fibrogenesis within the liver. Elegant T helper cell polarization studies have highlighted that critical control of Th1, Th2 and interleukin (IL)-17-secreting lymphocytes is necessary to prevent severe liver pathology. Alternatively activated macrophages develop in the Th2 milieu and upregulate Fizz1, Ym-1 and Arg-1. The possible contribution of macrophages to fibrogenesis and their role in immune regulation are discussed. Within the liver, natural (CD4(+)CD25(+) Forkhead box protein 3 (Foxp3)(+)) and inducible (CD4(+)Foxp3(-)) Treg's are recruited, providing an essential regulatory arm to stabilize the immune response and limit immunopathology. This review ties together current thinking of how the granulomatous response develops, causing much of the associated immunopathology, with extensive discussions on how regulatory cells and cytokine decoy receptors serve to limit the extent of immune-mediated pathology during schistosomiasis.

Opposing roles for IL-13 and IL-13 receptor alpha 2 in health and disease.

Interleukin (IL)-13 is a key inducer of several type-2 cytokine-dependent pathologies. It regulates inflammation, mucus production, tissue remodeling, and fibrosis. Consequently, it has become an important therapeutic target for a number of debilitating illnesses, including asthma, idiopathic pulmonary fibrosis, ulcerative colitis, as well as several other diseases in which IL-13 is believed to be overproduced. In the murine model of schistosomiasis, IL-13 has emerged as a central mediator of chronic infection-induced liver pathology. Although IL-4, IL-5, IL-10, and IL-13 each regulate distinct aspects of the granulomatous inflammatory response, IL-13 was identified as the primary mediator of liver fibrosis. Thus, elucidating the mechanisms that regulate the production and function of IL-13 has become an intensive area of research. IL-13 signaling is mediated by the type-2 IL-4 receptor, which consists of the IL-4R alpha and IL-13R alpha 1 chains. However, another IL-13-binding chain, IL-13R alpha 2, appears to strongly inhibit the activity of IL-13. Animals deficient in IL-13R alpha 2 fail to downmodulate granuloma formation in the chronic phase of infection. They also develop severe IL-13-dependent fibrosis and portal hypertension and quickly succumb to the infection. Here, we summarize findings from the schistosomiasis model, which illustrate opposing activities for IL-13 and IL-13R alpha 2 in health and disease.