Interleukin 4 and 13 participation in mycobacterial (type-1) and schistosomal (type-2) antigen-elicited pulmonary granuloma formation: multiparameter analysis of cellular recruitment, chemokine expression and cytokine networks

The Formation and Function of Granulomas

Granulomas are organized aggregates of macrophages, often with characteristic morphological changes, and other immune cells. These evolutionarily ancient structures form in response to persistent particulate stimuli-infectious or noninfectious-that individual macrophages cannot eradicate. Granulomas evolved as protective responses to destroy or sequester particles but are frequently pathological in the context of foreign bodies, infections, and inflammatory diseases. We summarize recent findings that suggest that the granulomatous response unfolds in a stepwise program characterized by a series of macrophage activations and transformations that in turn recruit additional cells and produce structural changes. We explore why different granulomas vary and the reasons that granulomas are protective and pathogenic. Understanding the mechanisms and role of granuloma formation may uncover new therapies for the multitude of granulomatous diseases that constitute serious medical problems while enhancing the protective function of granulomas in infections.

A randomized, controlled dose-finding Phase II study of the M72/AS01 candidate tuberculosis vaccine in healthy PPD-positive adults

Purpose

In this dose-finding Phase II study (NCT00621322), we evaluated the safety and immunogenicity of different formulations of the candidate tuberculosis vaccine containing the M72 antigen (10/20/40 μg doses) and the liposome-based AS01 Adjuvant System. We aimed to select the lowest-dose combination of M72 and AS01 that was clinically well tolerated with immunogenicity comparable to that of the previously tested M72/AS01_B (40 μg) candidate vaccine.

Methods

Healthy PPD-positive (induration 3–10 mm) adults (18–45 years) in The Philippines were randomized (4:4:4:4:1:1) to receive 2 injections, 1 month apart, of M72/AS01_B (40 μg), M72/AS01_E (10 μg), M72/AS01_E (20 μg), M72/AS02_D (10 μg), M72/Saline (40 μg) or AS01_B alone, and were followed up for 6 months. AS01_E and AS02_D contain half the quantities of the immunostimulants present in AS01_B. AS02_D is an oil-in-water emulsion. Vaccine selection was based on the CD4⁺ T-cell responses at 1 month post vaccination.

Results

All formulations had a clinically acceptable safety profile with no vaccine-related serious adverse events reported. Two vaccinations of each adjuvanted M72 vaccine induced M72-specific CD4⁺ T-cell and humoral responses persisting at 6 months post vaccination. No responses were observed with AS01_B alone. One month post second vaccination, CD4⁺ T-cell responses induced by each of the three M72/AS01 vaccine formulations were of comparable magnitudes, and all were significantly higher than those induced by M72/AS02_D (10 μg) and M72/Saline.

Conclusions

The formulation with the lowest antigen and adjuvant dose, M72/AS01_E (10 μg), fulfilled our pre-defined selection criteria and has been selected for further clinical development.

The linkage of innate and adaptive immune response during granulomatous development

Granulomas represent a spectrum of inflammatory sequestration responses that may be initiated by a variety of agents, including non-infectious environmental factors and infectious microbial pathogens. Although this reaction is designed to be protective, the associated tissue injury is often responsible for a profound degree of pathology. While many of the mechanisms that sustain the development of the granuloma are enigmatic, it is accepted that the maintenance of this inflammatory process is dependent upon dynamic interactions between an inciting agent, inflammatory mediators, various immune and inflammatory cells, and structural cells of the involved tissue. The best studied of the host-dependent processes during granuloma development is the innate and adaptive immune response. The innate immune response by antigen-presenting cells [APCs; dendritic cells (DCs) and macrophages] is initiated quickly to protect from overwhelming pathogens, but with time, can also activate the adaptive immune response. APCs, essential regulators of the innate immune response, can respond to microbial ligands through Toll-like receptors (TLRs), which function in the recognition of microbial components and play an important role to link the innate and adaptive immune responses. CD4(+) T helper (Th) cells are essential regulators of adaptive immune responses and inflammatory diseases. Recently, the Notch system has been shown to be an important bridge between APCs and T cell communication circuits. In the present review, we discuss recent findings that explore the mechanisms in the linkage of innate and adaptive immunity, including granulomatous formation though TLRs and Notch activation.

Dysregulated cytokine expression by CD4+ T cells from post-septic mice modulates both Th1 and Th2-mediated granulomatous lung inflammation

Previous epidemiological studies in humans and experimental studies in animals indicate that survivors of severe sepsis exhibit deficiencies in the activation and effector function of immune cells. In particular, CD4+ T lymphocytes can exhibit reduced proliferative capacity and improper cytokine responses following sepsis. To further investigate the cell-intrinsic defects of CD4+ T cells following sepsis, splenic CD4+ T cells from sham surgery and post-septic mice were transferred into lymphopenic mice. These recipient mice were then subjected to both TH1-(purified protein derivative) and TH2-(Schistosoma mansoni egg antigen) driven models of granulomatous lung inflammation. Post-septic CD4+ T cells mediated smaller TH1 and larger TH2 lung granulomas as compared to mice receiving CD4+ T cells from sham surgery donors. However, cytokine production by lymph node cells in antigen restimulation assays indicated increased pan-specific cytokine expression by post-septic CD4+ T cell recipient mice in both TH1 and TH2 granuloma models. These include increased production of T_H2 cytokines in TH1 inflammation, and increased production of T_H1 cytokines in TH2 inflammation. These results suggest that cell-intrinsic defects in CD4+ T cell effector function can have deleterious effects on inflammatory processes post-sepsis, due to a defect in the proper regulation of TH-specific cytokine expression.

Transgenic modelling of cytokine polarization in the lung

The lung is one of the commonest sites of exposure to environmental allergen or pathogen, so the expression of a variety of cytokines in the lung is dynamically regulated by inflammatory or structural cells in the lung. In the last decades, characterization of the local lung cytokine milieu in allergic or injury models has identified a collective role of certain cytokines, such as type 1 or type 2 cytokines, driving polarized inflammatory and tissue phenotypes. With the development of transgenic mouse modelling systems, the effector function of individual cytokine and the pathophysiological consequences of cytokine polarization in the lung have been effectively evaluated. Here, we present an overview of the transgenic systems currently used to assess the biological function of cytokine or other mediators in the lung. We discuss the inflammatory and tissue phenotypes detected in the lungs of transgenic mice over-expressing representative T helper type 1 (interferon-γ, interleukin-12), T helper type 2 (interleukins -4, -5, -9, -10 and -13), and T helper type 17 cytokines. The effects of genetic modification of cytokine receptors or transcriptional factors such as GATA-3 and T-bet in pulmonary inflammation and remodelling tissue responses are also discussed because these transcription factors are regarded as essential regulators of cytokine polarization. Finally, we discuss the limitations and future application of transgenic approaches in the studies of human lung diseases characterized by cytokine polarization.

Toll-like receptor 9 activation is a key mechanism for the maintenance of chronic lung inflammation

RATIONALE

Accumulating evidence supports the hypothesis that the continuous host response to a persistent challenge can polarize the cytokine environment toward a Th2 cytokine phenotype, but the mechanisms responsible for this skewing are not clear.

OBJECTIVES

We investigated the role of Toll-like receptor 9 (TLR9) in a Th2-driven pulmonary granulomatous response initiated via the embolization of Schistosoma mansoni eggs to the lungs of mice.

METHODS

Mice were intravenously injected with S. mansoni eggs. Histological and flow cytometric analysis, cytokine measurement, adoptive transfer of bone marrow (BM)-derived dendritic cells (DCs), and in vitro T-cell treatments with antigen-presenting cells were examined.

MEASUREMENTS AND MAIN RESULTS

In comparison to wild-type mice, TLR9(-/-) mice showed increased pulmonary granuloma size, augmented collagen deposition, increased Th2 cytokine phenotype, and impaired accumulation of DCs. BM-derived DCs, but not macrophages, recovered from animals with developed Th2-type lung granulomas promoted the production of type 2 cytokines from CD4(+) T cells. BM-derived DCs from TLR9(-/-) mice induced impaired Th1 cytokine and enhanced Th2 cytokine production by T cells, compared with DCs from WT mice. Macrophages from TLR9(-/-) mice expressed a significantly higher alternatively activated (M2) phenotype characterized by increased "found in inflammatory zone-1" (FIZZ1) and arginase-1 expression. The adoptive transfer of BM-derived DCs from syngeneic WT mice into TLR9(-/-) mice restored the granuloma phenotype seen in WT mice.

CONCLUSIONS

These studies suggest that TLR9 plays an important mechanistic role in the maintenance of the pulmonary granulomatous response.

Toll-like receptors, Notch ligands, and cytokines drive the chronicity of lung inflammation

Current dogma supports the concept that the expression of a disease-inducing signature cytokine phenotype is important to the maintenance stage of chronic lung disorders. This cytokine phenotype has been characterized as a polarization toward type 2 cytokines, which are profibrotic and immunoregulatory. The biology of this latter activity could mechanistically explain pathogen-induced exacerbation of chronic lung inflammation, as a skewed cytokine profile in the lung alters dendritic cell function, activates fibroblasts, and facilitates a subsequent "second hit" by an infectious pathogen. In this setting, cytokine biology is also linked to Toll-like receptors (TLRs) in the maintenance of lung immunity, as the activity of this receptor-ligand system by both leukocytes and stromal cells is likely an important component of disease chronicity. The participation of dendritic cells via TLRs in chronic lung disease could facilitate communication circuits established between antigen-presenting cells and lymphocytes. Data suggest that TLR activation via myeloid differentiation factor 88 adaptor protein leads to the induction of a Notch ligand known as Delta-like-4 on dendritic cells that activate the Notch receptor on T cells, promoting a helper T-cell type 1 cytokine response. It is likely that the evolution of host defense signals designed to recognize patterns emitted from a hostile microbial environment may now be superimposed on adaptive immunity and provide the underpinning to support the maintenance of chronic lung disease.

TLR9 activation is a key event for the maintenance of a mycobacterial antigen-elicited pulmonary granulomatous response

Type 1 (Th1) granulomas can be studied in mice sensitized with mycobacterium antigens followed by challenge of agarose beads covalently coupled to purified protein derivative. TLR9 is known to play a role in the regulation of Th1 responses; thus, we investigated the role of TLR9 in granuloma formation during challenge with mycobacterium antigens and demonstrated that mice deficient in TLR9 had increased granuloma formation, but a dramatically altered cytokine phenotype. Th1 cytokine levels of IFN-gamma and IL-12 in the lungs were decreased in TLR9(-/-) mice when compared to wild-type mice. In contrast, Th2 cytokine levels of IL-4, IL-5, and IL-13 were increased in TLR9(-/-) mice. The migration of CD4(+) T cells in the granuloma was impaired, while the number of F4/80(+) macrophages was increased in TLR9(-/-) mice. Macrophages in the lungs of the TLR9-deficient animals with developing granulomas expressed significantly lower levels of the classically activated macrophage marker, nitric oxide synthase, but higher levels of the alternatively activated macrophage markers such as 'found in inflammatory zone-1' antigen and Arginase-1. These results suggest that TLR9 plays an important role in maintaining the appropriate phenotype in a Th1 granulomatous response.

Mechanisms underlying reduced expulsion of a murine nematode infection during protein deficiency

Balb/c mice infected with the gastrointestinal nematode Heligmosomoides bakeri were fed protein sufficient (PS, 24%) or deficient (PD, 3%) diets to investigate whether diet, infection or dose of larval challenge (0, 100 or 200 larvae) influenced gut pathophysiology and inflammation. Among the PS mice, worms were more posteriorad in the intestine of mice infected with 200 compared with 100 larvae, suggesting active expulsion in the more heavily infected mice. This was consistent with the positive correlation between worm numbers and fluid leakage in PS mice; similar patterns were not detected in the PD mice. Infection also induced villus atrophy, which was more pronounced in PS than in PD mice. Our cytokine screening array indicated that infection in PD mice elevated a wide range of pro-inflammatory cytokines and chemokines. Whereas serum leptin concentrations were higher in PD mice, monocyte chemotactic protein-5 (MCP-5) in serum increased with increasing larval dose and concentrations were lower in PD than PS mice. We suggest that elevated MCP-5 together with villus atrophy may contribute to the apparent dose-dependent expulsion of H. bakeri from PS mice but that delayed expulsion in PD mice appeared related to a predominant Th1 cytokine profile that may be driven by leptin.

IL-13 is pivotal in the fibro-obliterative process of bronchiolitis obliterans syndrome

Acute allograft rejection is considered to be a predominately type 1 immune mediated response to the donor alloantigen. However, the type 2 immune mediated response has been implicated in multiple fibroproliferative diseases. Based on the fibro-obliterative lesion found during bronchiolitis obliterans syndrome (BOS), we hypothesized that the type 2 immune mediated response is involved in chronic lung allograft rejection. Specifically, whereas acute rejection is, in part, a type 1 immune response, chronic rejection is, in part, a type 2 immune response. We found the type 2 cytokine, IL-13, to be elevated and biologically active in human bronchoalveolar lavage fluid during BOS. Translational studies using a murine model of BOS demonstrated increased expression of IL-13 and its receptors that paralleled fibro-obliteration. In addition, in vivo neutralization of IL-13 reduced airway allograft matrix deposition and murine BOS, by a mechanism that was independent of IL-4. Furthermore, using IL-13Ralpha2(-/-) mice, we found increased fibro-obliteration. Moreover, anti-IL-13 therapy in combination with cyclosporin A had profound effects on reducing murine BOS. This supports the notion that IL-13 biological axis plays an important role during the pathogenesis of BOS independent of the IL-4 biological axis.

AMD3465, a novel CXCR4 receptor antagonist, abrogates schistosomal antigen-elicited (type-2) pulmonary granuloma formation

CXCR4 is a major receptor for CXCL12 and is known to participate in multiple physiological systems. The present study tested a second generation CXCR4 antagonist, AMD3465, for effects on highly defined models of Th1- and Th2-cell-mediated hypersensitivity-type pulmonary granuloma formation. Type-1 and type-2 granulomas were induced, respectively, by intravenous challenge of sensitized CBA/J mice with Mycobacteria bovis purified protein derivative- or Schistosoma mansoni egg antigen-coated beads. Before challenge, mice were implanted with osmotic pumps releasing AMD3465 at 5 microg/hour (6 mg/kg/day). Compared to vehicle, AMD3465 had minimal effect on type-1 inflammation or cytokine responses in draining lymph nodes, but the type-2 inflammation was significantly abrogated with reductions in lesion size and eosinophil content as well as abrogated interleukin (IL)-5, IL-10, and IL-13 cytokine production in draining lymph nodes. The biased effect of AMD3465 correlated with greater CXCR4 ligand expression in the type-2 model. Treatment during a primary response impaired lymph node IL-2 production after both Mycobacteria bovis purified protein derivative and Schistosoma mansoni egg antigen challenge indicating an unbiased effect during immune induction. In summary, CXCR4 blockade inhibited eosinophil recruitment during type-2 granuloma formation and interfered with primary and secondary T-cell activation events in lymphoid tissue, suggesting potential therapeutic application for chronic hypersensitivity diseases.

Analysis of inducible costimulatory molecule participation during the induction and elicitation of granulomatous responses to mycobacterial and schistosomal antigens

The contribution of inducible costimulatory molecule (ICOS) to Th1 and Th2 cell-mediated immune responses was examined in well-defined pathogen antigen-elicited models of cell-mediated granuloma formation. Th1 and Th2 granulomas were respectively induced by intravenous challenge of CBA/J mice with Mycobacteria bovis purified protein derivative (PPD) or Schistosoma mansoni egg (SEA) antigen-coated beads. Effects of anti-ICOS blocking antibody on granulomas and lymphoid responses were assessed during elicitation and sensitization. Anti-ICOS treatment during the elicitation abrogated Th1- but not Th2-cell-mediated granuloma formation. Treatment during sensitization augmented SEA-bead granulomas and Th2 cytokines in lymphoid tissue. Anti-ICOS reduced the primary inflammatory response to PPD- but not to SEA-beads, despite comparable induction of ICOS-ligand and ICOS+ T cells. Treatment did not prevent early development of IFNgamma producing cells. Thus, post-activation effector Th1 activity was subject to ICOS blockade and chronic treatment caused diversion to Th2 dominance likely by eroding Th1 effector function or survival.

Interleukin-25 and Interleukin-13 Production by Alveolar Macrophages in Response to Particles

Particle inhalation-induced lung inflammation acts as an adjuvant to allergens or respiratory viral infection in a process that is mediated by macrophages and epitheliums. The production of interleukin (IL)-4 and IL-13 by activated T cells is involved in the augmentation of Th2-type immune responses to particles, and IL-25 induces the synthesis of IL-4 and IL-13. However, whether IL-13 and IL-25 are directly regulated by particle instillation in the lung has not been studied. The aim of this study was to reveal particle induction of IL-13 and IL-25 in the lung. TiO(2) instillation potently induced the mRNA expression for IL-25 and IL-13 in lung tissue extracts 24 h after treatment, as compared with the sham group. Immunostaining for IL-25 and IL-13 showed strong positivity for macrophages in the inflammatory lung lesions of TiO(2)-treated rats. The alveolar macrophages expressed IL-25 and IL-13 24 h after in vitro stimulation with TiO(2) particles in dose- and time-dependent manners, with maximal induction at 24 and 48 h after stimulation, respectively. The sequence of the rat IL-25 gene is 95% homologous with the mouse IL-25 gene. These findings indicate that alveolar macrophages play an important role in particle-induced lung inflammation via direct induction of IL-13 and IL-25 production.

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.

Glycans of Schistosoma mansoni and keyhole limpet haemocyanin induce hepatic granulomas in vivo

Schistosoma mansoni eggs trapped in the liver of an infected host cause the major pathological manifestations of schistosomiasis. Miracidia within the deposited eggs secrete soluble egg antigens (SEA) that induce periovular granuloma formation, which may lead to severe hepatic fibrosis. Several reports have highlighted the immunomodulatory capacities of carbohydrate determinants present in the glycoproteins of SEA. These glycans contain among others the immunogenic Galbeta1-4(Fucalpha1-3)GlcNAc (LewisX) and GalNAcbeta1-4(Fucalpha1-2Fucalpha1-3)GlcNAc (LDN-DF) elements. Due to cross-reactivity with schistosomal glycan antigens, keyhole limpet haemocyanin (KLH) has been used extensively for diagnostic and therapeutic studies on schistosomiasis. In the present study, a granulomatous response with numerous eosinophils towards SEA- and KLH-coated beads implanted in the liver by mesenteric injection was observed. Immunophenotyping of these experimentally induced granulomas for cellular recruitment, chemokines, adhesion and extracellular matrix proteins revealed very close resemblance with hepatic lesions evoked by native schistosome eggs, hence demonstrating the usefulness of the bead model, in general, as well as of KLH as a model antigen to study the immunopathological mechanisms of schistosome infections. While trypsin digestion of KLH did not alter its antigenic characteristics, beads coated with SEA or KLH treated with sodium periodate to destroy the immunological properties of their carbohydrate chains, yielded only a monolayer of macrophages similar to negative control beads. Up-regulation of ICAM-1, LFA-1 and fibronectin in SEA-induced granulomas and in native and trypsinised KLH-induced granulomas indicates a major role of the carbohydrate elements of SEA and KLH in the initiation and homeostasis of the inflammatory response. These data provide new insights in the complex and multifactorial carbohydrate-dependent host-parasite immunological interactions.

The innate pulmonary granuloma: characterization and demonstration of dendritic cell recruitment and function

Granulomas are innate sequestration responses that can be modified by superimposed acquired immune mechanisms. The present study examined the innate stage of pulmonary granuloma responses to bead-immobilized Th1- and Th2-inducing pathogen antigens (Ags), Mycobacteria bovis purified protein derivative (PPD) and Schistosoma mansoni soluble egg Ags (SEA). Compared to a nonpathogen Ag, PPD and SEA bead elicited larger lesions with the former showing accelerated inflammation. Temporal analyses of cytokine and chemokine transcripts showed all Ag beads induced tumor necrosis factor-alpha mRNA but indicated biased interleukin (IL)-1, IL-6, and IL-12 expression with PPD challenge. All beads elicited comparable levels of CXCL9, CXL10, CCL2, CCL17, and CCL22 mRNA, but PPD beads caused biased CXCL2 CXCL5, CCL3, and CCL4 expression whereas both pathogen Ags induced CCL7. Immunohistochemical, electron microscopic, and flow cytometric analyses showed that Ag beads mobilized CD11c+ dendritic cells (DCs) of comparable maturation. Transfer of DCs from PPD Ag-challenged lungs conferred a Th1 anamnestic cytokine response in recipients. Surprisingly, transfer of DCs from the helminth SEA-challenged lungs did not confer the expected Th2 response, but instead rendered recipients incapable of Ag-elicited IL-4 production. These results provide in vivo evidence that lung DCs recruited under inflammatory conditions favor Th1 responses and alternative mechanisms are required for Th2 commitment.

P-selectin suppresses hepatic inflammation and fibrosis in mice by regulating interferon gamma and the IL-13 decoy receptor

The selectin family of cell adhesion molecules is widely thought to promote inflammatory reactions by facilitating leukocyte recruitment. However, it was unexpectedly found that mice with targeted deletion of the P-selectin gene (PsKO mice) developed unpolarized type 1/type 2 cytokine responses and severely aggravated liver pathology following infection with the type 2-promoting pathogen Schistosoma mansoni. In fact, liver fibrosis, which is dependent on interleukin 13 (IL-13), increased by a factor of more than 6, despite simultaneous induction of the antifibrotic cytokine interferon gamma (IFN-gamma). Inflammation, as measured by granuloma size, also increased significantly in the absence of P-selectin. When infected PsKO mice were treated with neutralizing anti-IFN-gamma monoclonal antibodies, however, granuloma size was restored to wild-type levels; this finding revealed the potent proinflammatory role of IFN-gamma when expressed concomitantly with IL-13. Untreated PsKO mice also exhibited a significant (sixfold) reduction in decoy IL-13 receptor (IL-13 receptor alpha-2) expression when compared with infected wild-type animals. It is noteworthy, however, that when decoy receptor activity was restored in PsKO mice by treatment with soluble IL-13 receptor alpha-2-Fc, the exacerbated fibrotic response was completely inhibited. Thus, reduced expression of the decoy IL-13 receptor mediated by the elevated type 1 cytokine response probably accounts for the enhanced activity of IL-13 in PsKO mice and for the resultant increase in collagen deposition. In conclusion, the current study has revealed the critical role of P-selectin in the progression of chronic liver disease caused by schistosome parasites. By suppressing IFN-gamma and up-regulating the decoy IL-13 receptor, P-selectin dramatically inhibits the pathologic tissue remodeling that results from chronic type 2 cytokine-mediated inflammation.

IL-13 effector functions

IL-13 was first recognized for its effects on B cells and monocytes, where it upregulated class II expression, promoted IgE class switching and inhibited inflammatory cytokine production. It was also thought to be functionally redundant with IL-4. However, studies conducted with knockout mice, neutralizing antibodies, and novel antagonists demonstrate that IL-13 possesses several unique effector functions that distinguish it from IL-4. Resistance to most gastrointestinal nematodes is mediated by type-2 cytokine responses, in which IL-13 plays a dominant role. By regulating cell-mediated immunity, IL-13 modulates resistance to intracellular organisms including Leishmania major, Leishmania mexicana, and Listeria monocytogenes. In the lung, IL-13 is the central mediator of allergic asthma, where it regulates eosinophilic inflammation, mucus secretion, and airway hyperresponsiveness. Manipulation of IL-13 effector function may also prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth. IL-13 can also inhibit tumor immunosurveillance. As such, inhibitors of IL-13 might be effective as cancer immunotherapeutics by boosting type-1-associated anti-tumor defenses. Finally, IL-13 was revealed as a potent mediator of tissue fibrosis in both schistosomiasis and asthma, which indicates that it is a key regulator of the extracellular matrix. The mechanisms that regulate IL-13 production and/or function have also been investigated, and IL-4, IL-12, IL-18, IFN-gamma, IL-10, TGF-beta, TNF-alpha, and the IL-4/IL-13 receptor complex play important roles. This review highlights the effector functions of IL-13 and describes multiple pathways for modulating its activity in vivo.

Cytokine expression pattern in benign prostatic hyperplasia infiltrating T cells and impact of lymphocytic infiltration on cytokine mRNA profile in prostatic tissue

The aim of the study is to characterize the type of immune response in benign prostatic hyperplasia (BPH) tissue. BPH tissue-derived T cells (n = 10) were isolated, activated (PMA + ionomycin), and analyzed for intracellular reactivity with anti-IFN-gamma and IL-2, -4, -5, -6, -10, and -13, as well as TNF-alpha and -beta by four-color flow cytometry. Lymphokine release was tested using Th1/Th2 cytokine bead arrays. The amount of IFN-gamma and IL-2, -4, -13, and TGF-beta mRNA expressed in normal prostate (n = 5) was compared with that in BPH tissue separated into segments with normal histology (n = 5), BPH histology with (n = 10) and without (n = 10) lymphocytic infiltration, and BPH nodules (n = 10). Expression of lymphokine receptors was analyzed by immunohistology, flow cytometry, and RT-PCR. We found that 28 +/- 18% of BPH T helper cells were IFN-gamma(+)/IL-4(-) Th1 cells, 10 +/- 2% were IFN-gamma(-)/IL-4(+) Th2, and 12 +/- 6% were IFN-gamma(+)/IL-4(+) Th0 cells. In relation, cytotoxic and double-negative BPH T lymphocytes showed a slight decrease in Th1 and Th0 in favor of Th2. In double-positive BPH T lymphocytes, the trend toward Th2 (35 +/- 15%) was significant (Th1: 12 +/- 7%; Th0: 5 +/- 4%). Lymphokine release upon stimulation was found in the case of IL-2, IL-5, IFN-gamma, and TNF-alpha > 4 microg; of IL-4 > 2 microg; and of IL-10 > 1 microg/ml. Expression of lymphokine mRNA in tissue was increased (2- to 10-fold) in infiltrated BPH specimens with and without BPH histology. The infiltrated BPH specimens with normal histology differed from those with BPH histology, most evident by the significant decrease in IFN-gamma and the increase in TGF-beta mRNA expression. Infiltrated BPH specimens with BPH histology expressed significantly more IFN-gamma (5-fold), IL-2 (10-fold), and IL-13 (2.8-fold) when compared with noninfiltrated BPH specimens. BPH nodules, however, showed the highest level of expression of IL-4 and IL-13, with only intermediate levels of IFN-gamma and very low levels of IL-2 mRNA. Immune response in histologically less transformed BPH specimens is primarily of type 1, whereas in chronically infiltrated nodular BPH and especially within BPH nodules, it is predominantly of type 0 or type 2.

Cytokine-chemokine networks in experimental mycobacterial and schistosomal pulmonary granuloma formation

Type-1 and type-2 lung granulomas, respectively, elicited by bead immobilized Mycobacteria bovis and Schistosoma mansoni egg antigens (Ags) display different patterns of chemokine expression. This study tested the hypothesis that chemokine expression patterns were related to upstream cytokine signaling. Using quantitative transcript analysis, we defined expression profiles for 16 chemokines and then examined the in vivo effects of neutralizing antibodies against interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-10, IL-12, and IL-13. Transcripts for CXCL2, -5, -9, -10, and -11 and the CCL chemokine, CCL3, and lymphotactin (XCL1), were largely enhanced by Th1-related cytokines, IFN-gamma or IL-12. Transcripts for CCL11, CCL22, CCL17, and CCL1 were enhanced largely by Th2-related cytokines, IL-4, IL-10, or IL-13. Transcripts for CCL4, CCL2, CCL8, CCL7, and CCL12 were potentially induced by either Th1- or Th2-related cytokines, although some of these showed biased expression. IFN-gamma and IL-4 enhanced the greatest complement of transcripts, and their neutralization had the greatest anti-inflammatory effect on type-1 and type-2 granulomas, respectively. Th1/Th2 cross-regulation was evident because endogenous Th2 cytokines inhibited type-1, whereas Th1 cytokines inhibited type-2 biased chemokines. These findings reveal a complex cytokine-chemokine regulatory network that dictates profiles of local chemokine expression during T cell-mediated granuloma formation.

Alternative activation of macrophages

The classical pathway of interferon-gamma-dependent activation of macrophages by T helper 1 (T(H)1)-type responses is a well-established feature of cellular immunity to infection with intracellular pathogens, such as Mycobacterium tuberculosis and HIV. The concept of an alternative pathway of macrophage activation by the T(H)2-type cytokines interleukin-4 (IL-4) and IL-13 has gained credence in the past decade, to account for a distinctive macrophage phenotype that is consistent with a different role in humoral immunity and repair. In this review, I assess the evidence in favour of alternative macrophage activation in the light of macrophage heterogeneity, and define its limits and relevance to a range of immune and inflammatory conditions.

Experimental models of Schistosoma mansoni infection

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly to our understanding of the pathology and pathogenesis of infection. We consider here hepatic and extrahepatic disease in models of acute and chronic infection. Experimental schistosome infections have also contributed more broadly to our understanding of granulomatous inflammation and our understanding of Th1 versus Th2 related inflammation and particularly to Th2-mediated fibrosis of the liver.

Interleukin-13 fusion cytotoxin arrests Schistosoma mansoni egg-induced pulmonary granuloma formation in mice

Schistosoma mansoni egg-induced lung pathology requires the actions of interleukin (IL)-4 and IL-13. Because receptors for IL-4 and IL-13 share chains, we examined the effect of a fusion protein comprised of IL-13 and Pseudomonas exotoxin (IL13-PE) on the development of pulmonary granulomas in mice. At day 8 after an intravenous injection of live S. mansoni eggs, whole lung samples from IL13-PE-treated mice exhibited significantly lower IL-4 and IL-13 gene expression, smaller granulomas, decreased collagen levels, and increased IL-13 receptor alpha2 gene expression compared to controls. The therapeutic effects of IL13-PE were also observed at day 16 despite the termination of IL13-PE treatment at day 8. These studies demonstrate that targeting IL-4- and IL-13- responsive cells with IL13-PE effectively arrests S. mansoni egg granuloma formation.

Eosinophil recruitment in type-2 hypersensitivity pulmonary granulomas: source and contribution of monocyte chemotactic protein-3 (CCL7)

Monocyte chemotactic protein-3 (MCP-3/CCL7) has potent eosinophil chemoattractant properties. The present study determined its relative contribution to the formation of Th2 cytokine-mediated (type-2) eosinophil-rich interstitial lung granulomas induced by antigens of Schistosoma mansoni eggs. Both MCP-3 transcripts and protein levels were more strongly expressed in lungs with type-2 than with type-1 (mycobacterial antigen-elicited Th1-mediated) granulomas. In vivo treatment with neutralizing antibodies demonstrated that MCP-3 abrogated eosinophil accumulation in type-2 lesions by 40 to 50%. Immunohistochemical staining revealed that MCP-3 localized to vessels in or near granulomas suggesting that endothelial cells were an important in situ source of MCP-3. Maximal MCP-3 transcript expression was abrogated by anti-interleukin-4 treatment. Furthermore, cultured mouse lung endothelial cells displayed augmented MCP-3 production in response to interleukin-4. Together, these results suggest that MCP-3 contributes to a significant component of eosinophil recruitment in the type-2 interstitial granuloma formation and Th2 cytokines promote its production.

Chemokine responses in schistosomal antigen-elicited granuloma formation

Host immune systems have evolved specialized responses to multicellular parasites. This is well represented by the type 2 granulomatous response to Schistosoma mansoni egg antigens, which is an eosinophil-rich inflammatory response mediated by Th2-associated cytokines. Using Ag-bead models of pulmonary granuloma formation in mice, we defined characteristic chemokine (CK) profiles in the granulomatous lungs. Our findings point to a role for C-C chemokine receptor-2 (CCR2) and CCR3 agonists such as monocyte chemotactic proteins (MCPs) 1/CCL2, 3/CCL7 and 5/CCL12 as important participants that are subject to regulation by Th2 cytokines interleukin (IL)-4 and IL-13. CCR4 and CCR8 agonists are also likely contributors. Analysis of CK receptor knockout mice revealed that CCR2 ligands (e.g. MCP-1 and 5) promoted early phase granuloma macrophage accumulation, whereas anti-MCP-3 (CCL7) antibody treatment abrogated eosinophil recruitment. CCR8 knockout mice also demonstrated impaired eosinophil recruitment but this appeared to be related to impaired Th2 cell function. Transcript analysis of CD4+ T cells generated during schistosome granuloma formation failed to show biased CCR8 expression but, having a more limited receptor repertoire, these cells were likely more dependent on CCR8 ligands. Together, these studies indicate an intricate involvement of chemokines in various stages and aspects of schistosomal egg Ag-elicited granuloma formation.

Differential effects of ageing on cytokine and chemokine responses during type-1 (mycobacterial) and type-2 (schistosomal) pulmonary granulomatous inflammation in mice

Cytokine and chemokine responses during anamnestic type-1 and type-2 lung granuloma formation were evaluated in mice at 6,12,18 and 24-months of age. Lesions were induced by embolizing Sepharose beads coupled to Mycobacterium bovis purified protein derivative or soluble Schistosoma mansoni egg antigens. Type-1 inflammation was reduced by 18 months, whereas type-2 granulomas not until 24 months of age. In type-1 draining lymph nodes cultures, interferon-gamma (IFNgamma) declined to a nadir by 18, and then partly recovered at 24 months. In contrast, IL-4 was not significantly impaired in type-2 cultures until 24 months. Type-1 and 2 node cultures also displayed decreased IL-13, but paradoxically enhanced IL-5 production at 24 months. Chemokine transcripts in granulomatous lungs displayed age-related alterations. In the type-1 response, CXCL9 (monokine-induced by IFNgamma) declined with age then partly recovered at 24 months parallelling lymph node IFNgamma levels. Transcripts for MIP-2/CXCL2, IP-10/CXCL10, MCP-1/CCL2, and MCP-5/CCL12 increased at 24 months. In the type-2 response MCP-1/CCL2, MCP-3/CCL7, MCP-5/CCL12 and TARC/CCL17 collapsed at 24 months paralleling local IL-4 transcript levels, yet some chemokine transcripts such as KC/CXCL1 and eotaxin/CCL11 were unaffected. These findings suggest that cytokine and chemokine responses degrade differentially with age shifting Th1/Th2 crossregulatory pressures and local expression of chemokines.

Interleukin-4 receptor-Stat6 signaling in murine infections with a tissue-dwelling nematode parasite

Interleukin-4 (IL-4) has been shown to be crucial in parasite expulsion in several gastrointestinal nematode infection models. Data from both epidemiological studies with humans and experimental infections in animals imply a critical role for the type II helper response, dominated by IL-4, in host protection. Here we utilized inbred mice on two distinct backgrounds to document the involvement of IL-4 in the clearance of a primary infection of Brugia from the murine host. Our data from infections of IL-4 receptor(-/-) and Stat6(-/-) mice further indicate that IL-4 exerts its effects by activating the Stat6 molecule in host target cells, a finding which links clearance requirements of a gastrointestinal tract-dwelling nematode with those of a tissue-dwelling nematode. Additionally, we show that the requirements for IL-4 receptor binding and Stat6 activation extend to accelerated clearance of a secondary infection as well. The data shown here, including analysis of cell populations at the site of infection and infection of immunoglobulin E (IgE)(-/-) mice, lead us to suggest that deficiencies in eosinophil recruitment and isotype switching to IgE production may be at least partially responsible for slower parasite clearance in the absence of IL-4.

IL-13 transgene state impairs mycobacterial (type-1) and schistosomal (type-2) antigen-elicited responses

Transgenic technology provides one approach for examining cytokine properties in vivo. This study directly tested the effect of a lung-targeted IL-13 transgene on the induction and elicitation of Th1 and Th2 cell-mediated immuno-inflammatory responses. Induction of Th1 (type 1) and Th2 (type 2) responses were tested by sensitization of IL-13 transgenics and littermates with purified protein derivative (PPD) of Mycobacterium bovis or Schistosoma mansoni eggs. Secondary elicitation of pulmonary granulomas was examined in adoptively sensitized transgenics and littermates challenged with bead-bound PPD or S. mansoni egg antigens. Parameters included lymphoid tissue cytokine profiles and granuloma sizes. Results showed that induction and elicitation of both type 1 and type 2 cytokines and granulomas were significantly abrogated in transgenics. Systemic effects were possible, as transgenic serum contained high levels of circulating IL-13. These findings support the concept that IL-13 impairs effector functions and provide novel information regarding its role in regulating Th2 cytokines.

Recombinant herpes simplex virus type 1 expressing murine interleukin-4 is less virulent than wild-type virus in mice

The effect of interleukin-4 (IL-4) on herpes simplex virus type 1 (HSV-1) infection in mice was evaluated by construction of a recombinant HSV-1 expressing the gene for murine IL-4 in place of the latency-associated transcript (LAT). The mutant virus (HSV-IL-4) expressed high levels of IL-4 in cultured cells. The replication of HSV-IL-4 in tissue culture and in trigeminal ganglia was similar to that of wild-type virus. In contrast, HSV-IL-4 appeared to replicate less well in mouse eyes and brains. Although BALB/c mice are highly susceptible to HSV-1 infection, ocular infection with HSV-IL-4 resulted in 100% survival. Furthermore, 57% of the mice survived coinfection with a mixture of HSV-IL-4 and a lethal dose of wild-type McKrae, compared with only 10% survival following infection with McKrae alone. Similar to wild-type BALB/c mice, 100% of IL-4(-/-) mice also survived HSV-IL-4 infection. T-cell depletion studies suggested that protection against HSV-IL-4 infection was mediated by a CD4(+)-T-cell response.

Chemokine expression dynamics in mycobacterial (type-1) and schistosomal (type-2) antigen-elicited pulmonary granuloma formation

Transcript expression of 24 chemokines (CKs) was examined throughout 8 days in mouse lungs with type-1 (Th1) or type-2 (Th2) cytokine-mediated granulomas induced by bead-immobilized mycobacterial purified protein derivative or Schistosoma mansoni egg antigens. Where possible, CK protein levels were also measured. In addition, we examined effects of in vivo cytokine depletions. Findings were as follows: 1) bead challenge induced increases in 18 of 24 CK transcripts with type-1 and type-2 responses displaying different patterns. CKs fell into four categories: a) type-1-dominant (gamma-interferon-inducible protein (IP-10), monokine induced by INF-gamma (MIG), macrophage inflammatory protein-2 (MIP-2), lipopolysaccharide-induced chemokine (LIX), rodent growth-related oncogene homologue (KP), macrophage inflammatory protein-1alpha (MIP-1alpha) and -1beta (MIP-1beta), lymphotactin), b) type-2-dominant (eotaxin, monocyte chemotactic protein-2 (MCP-2) and -3 (MCP-3), liver and activation-regulated chemokine (LARC), T cell activation protein-3 (TCA-3), c) type-1 and type-2 co-dominant (MCP-1, MCP-5, monocyte-derived chemokine (MDC), thymus and activation-related chemokine (TARC), C10), and d) constitutive (lungkine, secondary lymphoid-tissue chemokine (SLC), EBI1-ligand chemokine (ELC), fractalkine, macrophage inflammatory protein-1gamma (MIP1-gamma), and stromal cell derived factor-1alpha (SDF1-alpha). 2) CKs displayed characteristic temporal patterns. CXC (IP-10, MIG, MIP-2, LIX, KC) and certain CC (MCP-1, MCP-5, MIP-1alpha, MIP-1beta) CKs were produced maximally within 1 to 2 days. Others (MCP-2, MCP-3, eotaxin, lymphotactin, LARC, TCA-3) displayed peak expression later. 3) Interferon-gamma neutralization profoundly abrogated MIG, but had little effect on other CKs. Tumor necrosis factor-alpha neutralization caused up to 50% reduction in a range of CKs. These findings indicate that type-1 and type-2 granulomas display characteristic CK profiles with coordinated expression that is under cytokine-mediated regulation.

Contribution of Th1 and Th2 cells to protection and pathology in experimental models of granulomatous lung disease

Mice that had received adoptive transfer of DO11.10 TCR transgenic T cells polarized toward a Th1 or a Th2 phenotype were challenged with Ag-coated beads or with recombinant Mycobacterium tuberculosis expressing the OVA determinant. The resulting bead-induced pulmonary granulomas reflected the phenotype of the adoptively transferred T cells, with the Th2 cells promoting a fibrotic reaction. Mice receiving Th1 cells mounted an epitope-specific protective response to challenge with recombinant M. tuberculosis. Th2 recipients were characterized by enhanced weight loss and lung fibrosis during acute high-dose infection. The combination of TCR transgenic T cells and epitope-tagged mycobacteria provides a novel experimental model for investigation of the pathogenesis of tuberculosis.