Macrophages are critical to the maintenance of IL-13-dependent lung inflammation and fibrosis.

The roles of macrophages in type 2-driven inflammation and fibrosis remain unclear. Here, using CD11b-diphtheria toxin receptor (DTR) transgenic mice and three models of interleukin 13 (IL-13)-dependent inflammation, fibrosis, and immunity, we show that CD11b(+) F4/80(+) Ly6C(+) macrophages are required for the maintenance of type 2 immunity within affected tissues but not secondary lymphoid organs. Direct depletion of macrophages during the maintenance or resolution phases of secondary Schistosoma mansoni egg-induced granuloma formation caused a profound decrease in inflammation, fibrosis, and type 2 gene expression. Additional studies with CD11c-DTR and CD11b/CD11c-DTR double-transgenic mice suggested that macrophages but not dendritic cells were critical. Mechanistically, macrophage depletion impaired effector CD4(+) T helper type 2 (Th2) cell homing and activation within the inflamed lung. Depletion of CD11b(+) F4/80(+) Ly6C(+) macrophages similarly reduced house dust mite-induced allergic lung inflammation and suppressed IL-13-dependent immunity to the nematode parasite Nippostrongylus brasiliensis. Consequently, therapeutic strategies targeting macrophages offer a novel approach to ameliorate established type 2 inflammatory diseases.

The TNF-family cytokine TL1A promotes allergic immunopathology through group 2 innate lymphoid cells.

The tumor necrosis factor (TNF)-family cytokine TL1A (TNFSF15) costimulates T cells and promotes diverse T cell-dependent models of autoimmune disease through its receptor DR3. TL1A polymorphisms also confer susceptibility to inflammatory bowel disease. Here, we find that allergic pathology driven by constitutive TL1A expression depends on interleukin-13 (IL-13), but not on T, NKT, mast cells, or commensal intestinal flora. Group 2 innate lymphoid cells (ILC2) express surface DR3 and produce IL-13 and other type 2 cytokines in response to TL1A. DR3 is required for ILC2 expansion and function in the setting of T cell-dependent and -independent models of allergic disease. By contrast, DR3-deficient ILC2 can still differentiate, expand, and produce IL-13 when stimulated by IL-25 or IL-33, and mediate expulsion of intestinal helminths. These data identify costimulation of ILC2 as a novel function of TL1A important for allergic lung disease, and suggest that TL1A may be a therapeutic target in these settings.

IL-1α released from damaged epithelial cells is sufficient and essential to trigger inflammatory responses in human lung fibroblasts.

Activation of the innate immune system plays a key role in exacerbations of chronic lung disease, yet the potential role of lung fibroblasts in innate immunity and the identity of epithelial danger signals (alarmins) that may contribute to this process are unclear. The objective of the study was to identify lung epithelial-derived alarmins released during endoplasmic reticulum stress (ER stress) and oxidative stress and evaluate their potential to induce innate immune responses in lung fibroblasts. We found that treatment of primary human lung fibroblasts (PHLFs) with conditioned media from damaged lung epithelial cells significantly upregulated interleukin IL-6, IL-8, monocyte chemotactic protein-1, and granulocyte macrophage colony-stimulating factor expression (P<0.05). This effect was reduced with anti-IL-1α or IL-1Ra but not anti-IL-1ß antibody. Costimulation with a Toll-like receptor 3 ligand, polyinosinic-polycytidylic acid (poly I:C), significantly accentuated the IL-1α-induced inflammatory phenotype in PHLFs, and this effect was blocked with inhibitor of nuclear factor kappa-B kinase subunit beta and TGFß-activated kinase-1 inhibitors. Finally, Il1r1-/- and Il1a-/- mice exhibit reduced bronchoalveolar lavage (BAL) neutrophilia and collagen deposition in response to bleomycin treatment. We conclude that IL-1α plays a pivotal role in triggering proinflammatory responses in fibroblasts and this process is accentuated in the presence of double-stranded RNA. This mechanism may be important in the repeated cycles of injury and exacerbation in chronic lung disease.

The TNF-family cytokine TL1A drives IL-13-dependent small intestinal inflammation.

The tumor necrosis factor (TNF)-family cytokine TL1A (TNFSF15) costimulates T cells through its receptor DR3 (TNFRSF25) and is required for autoimmune pathology driven by diverse T-cell subsets. TL1A has been linked to human inflammatory bowel disease (IBD), but its pathogenic role is not known. We generated transgenic mice that constitutively express TL1A in T cells or dendritic cells. These mice spontaneously develop IL-13-dependent inflammatory small bowel pathology that strikingly resembles the intestinal response to nematode infections. These changes were dependent on the presence of a polyclonal T-cell receptor (TCR) repertoire, suggesting that they are driven by components in the intestinal flora. Forkhead box P3 (FoxP3)-positive regulatory T cells (Tregs) were present in increased numbers despite the fact that TL1A suppresses the generation of inducible Tregs. Finally, blocking TL1A-DR3 interactions abrogates 2,4,6 trinitrobenzenesulfonic acid (TNBS) colitis, indicating that these interactions influence other causes of intestinal inflammation as well. These results establish a novel link between TL1A and interleukin 13 (IL-13) responses that results in small intestinal inflammation, and also establish that TL1A-DR3 interactions are necessary and sufficient for T cell-dependent IBD.

Pulmonary fibrosis: pathogenesis, etiology and regulation.

Pulmonary fibrosis and architectural remodeling of tissues can severely disrupt lung function, often with fatal consequences. The etiology of pulmonary fibrotic diseases is varied, with an array of triggers including allergens, chemicals, radiation and environmental particles. However, the cause of one of the most common pulmonary fibrotic conditions, idiopathic pulmonary fibrosis (IPF), is still unclear. This review examines common mechanisms of pulmonary wound-healing responses following lung injury, and highlights the pathogenesis of some of the most widespread pulmonary fibrotic diseases. A three phase model of wound repair is reviewed that includes; (1) injury; (2) inflammation; and (3) repair. In most pulmonary fibrotic conditions dysregulation at one or more of these phases has been reported. Chronic inflammation can lead to an imbalance in the production of chemokines, cytokines, growth factors, and disrupt cellular recruitment. These changes coupled with excessive pro-fibrotic IL-13 and/or TGFbeta1 production can turn a well-controlled healing response into a pathogenic fibrotic response. Endogenous regulatory mechanisms are discussed including novel areas of therapeutic intervention. Restoring homeostasis to these dysregulated healing responses, or simply neutralizing the key pro-fibrotic mediators may prevent or slow the progression of pulmonary fibrosis.

Characterization of the divergent eosinophil ribonuclease, mEar 6, and its expression in response to Schistosoma mansoni infection in vivo.

The eosinophil-associated ribonucleases (Ears) are rapidly evolving proteins found in multigene clusters that are unique to each rodent species. Of the 15 independent genes in the Mus musculus cluster, only mEars 1 and 2 are expressed at significant levels at homeostasis. Here we characterize the expression of mEar 6 in the liver and spleen in mice in response to infection with the helminthic parasite, Schistosoma mansoni. Interestingly, expression of mEar 6 is not directly related to the elevated levels of serum IL-5 or tissue eosinophilia characteristic of this disease, as no mEar 6 transcripts were detected in the liver or the spleen from uninfected IL-5-transgenic mice. The coding sequence of mEar 6 has diverged under positive selection pressure (K(a)/K(s) > 1.0) and has a unique unpaired cysteine near the carboxy-terminus of the protein. The high catalytic efficiency of recombinant mEar 6 (k(cat)/K(m) = 0.9 x 10(6)/M/s) is similar to that of the cluster's closest human ortholog, eosinophil-derived neurotoxin (EDN/RNase 2). In summary, we have identified mEar 6 as one of only two RNase A superfamily ribonucleases known to be expressed specifically in response to pathophysiologic stress in vivo.

Differential regulation of nitric oxide synthase-2 and arginase-1 by type 1/type 2 cytokines in vivo: granulomatous pathology is shaped by the pattern of L-arginine metabolism.

Type 2 cytokines regulate fibrotic liver pathology in mice infected with Schistosoma mansoni. Switching the immune response to a type 1-dominant reaction has proven highly effective at reducing the pathologic response. Activation of NOS-2 is critical, because type 1-deviated/NO synthase 2 (NOS-2)-deficient mice completely fail to control their response. Here, we demonstrate the differential regulation of NOS-2 and arginase type 1 (Arg-1) by type 1/type 2 cytokines in vivo and for the first time show a critical role for arginase in the pathogenesis of schistosomiasis. Using cytokine-deficient mice and two granuloma models, we show that induction of Arg-1 is type 2 cytokine dependent. Schistosome eggs induce Arg-1, while Mycobacterium avium-infected mice develop a dominant NOS-2 response. IFN-gamma suppresses Arg-1 activity, because type 1 polarized IL-4/IL-10-deficient, IL-4/IL-13-deficient, and egg/IL-12-sensitized animals fail to up-regulate Arg-1 following egg exposure. Notably, granuloma size decreases in these type-1-deviated/Arg-1-unresponsive mice, suggesting an important regulatory role for Arg-1 in schistosome egg-induced pathology. To test this hypothesis, we administered difluoromethylornithine to block ornithine-aminodecarboxylase, which uses the product of arginine metabolism, L-ornithine, to generate polyamines. Strikingly, granuloma size and hepatic fibrosis increased in the ornithine-aminodecarboxylase-inhibited mice. Furthermore, we show that type 2 cytokine-stimulated macrophages produce proline under strict arginase control. Together, these data reveal an important regulatory role for the arginase biosynthetic pathway in the regulation of inflammation and demonstrate that differential activation of Arg-1/NOS-2 is a critical determinant in the pathogenesis of granuloma formation.

Patterns of chemokine expression in models of Schistosoma mansoni inflammation and infection reveal relationships between type 1 and type 2 responses and chemokines in vivo.

To explore the roles of chemokines in type 1 and type 2 responses in vivo, we examined mRNA expression for a panel of up to 17 chemokines in experimental mouse models using Schistosoma mansoni. These studies revealed that Mig (monokine induced by gamma interferon), cytokine-responsive gene 2/10-kDa interferon-inducible protein, RANTES, lymphotactin, macrophage inflammatory protein 1beta (MIP-1beta), JE/monocyte chemoattractant protein 1, and MIP-2 are associated with type 1 egg-induced responses and that thymus-derived chemotactic agent 3 (TCA3), eotaxin, MIP-1alpha, and MIP-1gamma are associated with type 2 egg-induced responses. After cercarial infection, both type 1-associated and type 2-associated chemokines were elevated in the livers of infected mice presensitized with eggs and recombinant interleukin-12 (rIL-12), a regimen that diminishes pathology. Neutralization of IL-12 or gamma interferon during egg deposition reversed the effects of prior treatment with rIL-12, leading to a return to larger granulomas; persistently elevated expression of TCA3, eotaxin, and MIP-1alpha; and a marked reduction in the expression of type 1-associated chemokines despite the maintenance of a dominant type 1 cytokine response in the draining lymph nodes. Our findings suggest that there are patterns of coordinate chemokine expression characteristic of type 1 and type 2 responses in vivo; that the cells recruited by a given pattern of chemokines may differ, depending on the composition of peripheral populations; and that patterns of tissue expression of chemokines may determine the character of an inflammatory response independently of the dominant pattern of differentiation of antigen-specific T cells. Our data reveal new relationships between chemokines and polarized immune responses and suggest that end organ inflammation might be altered by chemokine blockade without necessitating reversal of the phenotype of the majority of differentiated T cells.

Disease fingerprinting with cDNA microarrays reveals distinct gene expression profiles in lethal type 1 and type 2 cytokine-mediated inflammatory reactions.

Development of polarized immune responses controls resistance and susceptibility to many microorganisms. However, studies of several infectious, allergic, and autoimmune diseases have shown that chronic type-1 and type-2 cytokine responses can also cause significant morbidity and mortality if left unchecked. We used mouse cDNA microarrays to molecularly phenotype the gene expression patterns that characterize two disparate but equally lethal forms of liver pathology that develop in Schistosoma mansoni infected mice polarized for type-1 and type-2 cytokine responses. Hierarchical clustering analysis identified at least three groups of genes associated with a polarized type-2 response and two linked with an extreme type-1 cytokine phenotype. Predictions about liver fibrosis, apoptosis, and granulocyte recruitment and activation generated by the microarray studies were confirmed later by traditional biological assays. The data show that cDNA microarrays are useful not only for determining coordinated gene expression profiles but are also highly effective for molecularly "fingerprinting" diseased tissues. Moreover, they illustrate the potential of genome-wide approaches for generating comprehensive views on the molecular and biochemical mechanisms regulating infectious disease pathogenesis.

Helicobacter hepaticus-induced colitis in interleukin-10-deficient mice: cytokine requirements for the induction and maintenance of intestinal inflammation.

We have previously shown that specific-pathogen-free interleukin-10 (IL-10)-deficient (IL-10 KO) mice reconstituted with Helicobacter hepaticus develop severe colitis associated with a Th1-type cytokine response. In the present study, we formally demonstrate that IL-12 is crucial for disease induction, because mice deficient for both IL-10 and IL-12 p40 show no intestinal pathology following H. hepaticus infection. By using monoclonal antibodies (MAbs) to IL-12, gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha), we have further analyzed the role of these cytokines in the maintenance of the Th1 response and inflammation in IL-10 KO mice with established H. hepaticus-induced colitis. Treatment of infected colitic IL-10 KO mice with anti-IL-12 p40 resulted in markedly reduced intestinal inflammation, colonic IFN-gamma, TNF-alpha, and inducible nitric oxide synthase (iNOS) mRNA levels, and H. hepaticus-specific IFN-gamma secretion by mesenteric lymph node (MLN) cells compared to the findings in control MAb-treated mice. Moreover, the diminished pathology was associated with decreased numbers of colonic CD3(+) T cells and significantly reduced frequencies of Helicobacter-reactive CD4(+) Th1 cells in MLN. In contrast, anti-IFN-gamma and/or anti-TNF-alpha had no effect on intestinal inflammation in IL-10 KO mice with established colitis. Using IL-10/IFN-gamma double-deficient mice, we further show that IFN-gamma is not required for the development of colitis following H. hepaticus infection. MLN cells from infected IL-10/IFN-gamma KO animals secreted elevated amounts of IL-12 and TNF-alpha following bacterial antigen stimulation, indicating alternative pathways of disease induction. Taken together, our results demonstrate a crucial role for IL-12 in both inducing and sustaining intestinal inflammation through recruitment and maintenance of a pool of pathogenic Th1 cells.

NOS-2 mediates the protective anti-inflammatory and antifibrotic effects of the Th1-inducing adjuvant, IL-12, in a Th2 model of granulomatous disease.

Mice sensitized with SCHISTOSOMA: mansoni eggs and IL-12 develop liver granulomas, on subsequent infection, which are smaller and less fibrotic than those in nonsensitized mice. The protective response is accompanied by a shift in the type-2 cytokine profile to one dominated by type-1 cytokines. The deviated response is associated with marked increases in inducible nitric oxide synthase (NOS-2) activity. Here, we demonstrate, by using NOS-2-deficient mice, that the anti-inflammatory and anti-fibrotic effects of the type-1 response are completely NOS-2-dependent. Strikingly, despite developing a polarized type-1 cytokine response that was similar in magnitude, the egg/IL-12-sensitized NOS-deficient mice developed granulomas 8 times larger than WT mice did. There was also no decrease in hepatic fibrosis in the sensitized mutant animals. Interferon-gamma-deficient mice failed to exhibit the exacerbated inflammatory response, despite displaying a marked deficiency in nitric oxide production. However, immune deviation was unsuccessful in the latter animals, which suggested that the increase in inflammation in NOS-deficient mice resulted from a polarized but nitric oxide-deficient type-1 response. These results reveal a beneficial role for NOS-2 in the regulation of inflammation and suggest that the ultimate success of Th2-to-Th1 immune deviation strategies will rely on the efficient activation of NOS-2 expression in downstream effector cells.

IL-10 and the dangers of immune polarization: excessive type 1 and type 2 cytokine responses induce distinct forms of lethal immunopathology in murine schistosomiasis.

To dissect the controversial roles of type 1 and type 2 cytokines to the pathogenesis of schistosomiasis, we generated IL-10/IL-4- and IL-10/IL-12-deficient mice that develop highly polarized type 1 and type 2 cytokine responses, respectively. Interestingly, the Th1-polarized IL-10/IL-4-deficient mice rapidly lost weight at the onset of egg-laying and displayed 100% mortality by wk 9 postinfection. This acute mortality was linked to overexpression of the proinflammatory mediators IFN-gamma, TNF-alpha, and inducible NO and the formation of nonfibrotic granulomas. Elevated serum aspartate transaminase levels confirmed that mortality was in part attributable to acute hepatotoxicity. In contrast, the Th2-polarized IL-10/IL-12-deficient mice developed a progressive wasting disease that correlated with increased hepatic fibrosis, formation of large eosinophil-rich granulomas, a 10-fold increase in IL-4 and IL-13, and significant mortality during the chronic stages of infection. Surprisingly, IL-10-deficient mice displayed pathological features that were characteristic of both extremes, while wild-type mice developed relatively successful long term chronic infections. These data demonstrate that IL-10 significantly suppresses type 1 and type 2 cytokine development in IL-4- and IL-12-deficient mice, respectively, thereby impeding the development of severe egg-induced pathology in the single cytokine-deficient animals. Together, these findings reveal the central regulatory role of IL-10 in the pathogenesis of schistosomiasis and illustrate that excessive type 1 and type 2 cytokine responses trigger distinct, but equally detrimental, forms of pathology following infection.

CpG oligonucleotides can prophylactically immunize against Th2-mediated schistosome egg-induced pathology by an IL-12-independent mechanism.

Using a Schistosoma mansoni egg-induced granuloma model, we examined the ability of CpG oligodeoxynucleotides (ODN) to suppress Th2-type cytokine expression and to prophylactically immunize against Th2-dependent pulmonary pathology. The mechanism was examined by studying Th2 response regulation in cytokine-deficient mice. Surprisingly, our findings revealed several functions of CpG DNA that were completely IL-12 independent. Most striking was the marked suppression in Th2 cytokine expression and granulomatous inflammation observed in egg/CpG-sensitized IL-12-deficient mice. Immune deviation was not dependent on NK or B cells. However, a role for IL-10, B7.1, and CD40 expression in Th2 response inhibition was suggested. Indeed, CpG ODN up-regulated all three elements in both wild-type and IL-12-deficient mice. The role of IL-10 was demonstrated in mice exhibiting combined deficiencies in IL-12 and IL-10. Here, a marked increase in egg-specific IL-4/IL-5-producing cells confirmed a role for both cytokines in Th2 response inhibition. Nevertheless, the frequency of Th2-producing cells was again reduced by CpG ODN. However, in marked contrast to IL-12-deficient animals, a significant increase in IFN-gamma-producing cells likely explains the reduced Th2 response in IL-10/IL-12-deficient mice. Thus, a novel IL-12-independent type 1-inducing pathway was revealed in the combined absence of IL-12 and IL-10. Together, these data demonstrate 1) that the Th1-promoting activity of CpG DNA is controlled by IL-12 and IL-10, and 2) that Th2 response inhibition by CpG ODN involves IL-12-independent changes in IL-10 and costimulatory molecule expression. These findings illustrate the utility of CpG DNA as adjuvants for vaccines designed to prevent Th2-dependent immunopathology.

An IL-13 inhibitor blocks the development of hepatic fibrosis during a T-helper type 2-dominated inflammatory response.

In schistosomiasis, chronic parasite egg-induced granuloma formation can lead to tissue destruction and fibrosis, which causes much of the morbidity and mortality associated with this disease. Here we show the importance of IL-13 in the pathogenesis of schistosomiasis, and demonstrate, perhaps for the first time, the therapeutic efficacy of an IL-13 inhibitor, sIL-13Ralpha2-Fc, in the control of hepatic fibrosis. T-helper type 2 (Th2) cytokines dominate the immune response in mice infected with Schistosoma mansoni, yet the specific contributions of IL-13 and IL-4 to the development of fibrosis were not previously investigated. Our studies demonstrate that both cytokines play redundant roles in granuloma formation, which explains the ability of IL-4-deficient mice to form granulomas around eggs. More importantly, however, these studies demonstrate that IL-13 is the dominant Th2-type cytokine regulating fibrosis. IL-13 stimulated collagen production in fibroblasts, and procollagen I and procollagen III mRNA expression was decreased in sIL-13Ralpha2-Fc-treated mice. Moreover, the reduction in fibrosis observed in IL-4-deficient mice was much less pronounced than that in sIL-13Ralpha2-Fc-treated animals. Fibrosis is a major pathological manifestation of a number of allergic, autoimmune, and infectious diseases. Thus, our findings provide evidence that IL-13 inhibitors may be of general therapeutic benefit in preventing damaging tissue fibrosis resulting from Th2-dominated inflammatory responses.

Interleukin-12 can directly induce T-helper 1 responses in interferon-gamma (IFN-gamma) receptor-deficient mice, but requires IFN-gamma signalling to downregulate T-helper 2 responses.

An in vivo model of pulmonary granuloma formation around embolized schistosome eggs was investigated as an environment in which to analyse a role for interleukin-12 (IL-12) in the differentiation of T-helper 1 (Th1) and Th2 subsets. Specifically, mice deficient for the interferon-gamma receptor (IFN-gammaR-/-) were used to determine the role for IL-12 in the absence of IFN-gamma-mediated signalling. We show that recombinant IL-12 administered to IFN-gammaR-/- mice caused the up-regulation of mRNA for IFN-gamma in lung tissue, and the secretion of abundant IFN-gamma by in vitro-cultured lymph node cells in response to egg antigens. This indicates that IL-12 can act independently of IFN-gamma to induce the development of Th1 cells. Administration of rIL-12 to wild-type mice markedly reduced the secretion of Th2-associated cytokines, IL-4 and IL-5. However, these cytokines were not dramatically reduced in IFN-gammaR-/- mice treated with IL-12. We conclude that inhibition of these cytokines by IL-12 is primarily dependent upon effective IFN-gamma signalling, although abrogation of T-cell derived IL-10 appeared to be dependent upon IL-12. We also show that increases in mRNA for the beta2 subunit of the IL-12 receptor and the p40 subunit of IL-12 after rIL-12 treatment were lower in IFN-gammaR-/- mice, compared to wild-type mice, indicating that their expression was primarily dependent upon IFN-gamma with only a minor role for IL-12.

Egg laying is delayed but worm fecundity is normal in SCID mice infected with Schistosoma japonicum and S. mansoni with or without recombinant tumor necrosis factor alpha treatment.

Mice with severe combined immunodeficiency (SCID mice) lack functional B and T cells. Egg laying by Schistosoma mansoni and S. japonicum was delayed in SCID mice, but in a matter of weeks worm fecundity was equivalent to that in intact mice. SCID mice formed smaller hepatic granulomas and showed less fibrosis than did intact mice. The reduction in egg-associated pathology in SCID mice correlated with marked reductions in interleukin-4 (IL-4), IL-5, IL-13, and gamma interferon mRNA expression in the liver. S. mansoni infections were frequently lethal for SCID mice infected for more than 9 weeks, while S. japonicum-infected SCID mice died at the same rate as infected intact mice. We were unable to affect hepatic granuloma formation or egg laying by worms in SCID mice by administration of recombinant murine tumor necrosis factor alpha (TNF-alpha). In fact, SCID and BALB/c mice appeared to express nearly equivalent levels of TNF-alpha mRNA in their granulomatous tissues, suggesting that there is little or no deficit in TNF-alpha expression in infected SCID mice. The data indicate that TNF-alpha may be in large part derived from a non-T-cell source. Together, these findings provide little evidence that TNF-alpha alone can reconstitute early fecundity, granuloma formation, or hepatic fibrosis in schistosome-infected SCID mice.

The p47(phox-/-) mouse model of chronic granulomatous disease has normal granuloma formation and cytokine responses to Mycobacterium avium and Schistosoma mansoni eggs.

Chronic granulomatous disease (CGD) is a genetic disorder of NADPH oxidase in which phagocytes are defective in generating reactive oxidants. CGD patients suffer from recurrent infections and exuberant and persistent tissue granuloma formation. We hypothesized that abnormal granulomata in CGD may result from aberrant T-cell-mediated cytokine responses. To assess Th-1-type cytokine responses and granulomata, we challenged p47(phox-/-) and wild-type mice with avirulent (SmD) or virulent (SmT) variants of Mycobacterium avium 2-151. To assess Th-2-type cytokine responses and granulomata, we used Schistosoma mansoni eggs (SME). Mononuclear cells were harvested, and cytokine responses were determined by enzyme-linked immunosorbent assay or reverse transcriptase PCR. Following SmD or SmT challenge, splenocytes from p47(phox-/-) and wild-type mice generated similar polar Th-1 responses (increased levels of gamma interferon and basal levels of interleukin 4 [IL-4] and IL-5). By 8 weeks after SmT challenge, exuberant splenic granulomata developed in p47(phox-/-) and wild-type mice. After SME challenge, thoracic lymph node mononuclear cells from p47(phox-/-) and wild-type mice generated similar mixed Th-1 and Th-2 cytokine responses to SME antigen and concanavalin A. Peak lung granuloma sizes and rates of regression were similar in p47(phox-/-) and wild-type mice. These results suggest that exuberant granulomatous inflammation in CGD is probably not the result of skewing of T-cell responses toward the Th-1 or Th-2 pole. Appropriate regression of established tissue granulomata in p47(phox-/-) mice challenged with SME suggests that abnormal granuloma formation in CGD is stimulus dependent and is not an invariant feature of the disease.

Optimal vaccination against Schistosoma mansoni requires the induction of both B cell- and IFN-gamma-dependent effector mechanisms.

Mice immunized with radiation-attenuated cercariae of Schistosoma mansoni display resistance to challenge infection, which increases with multiple boosting. Protection in animals receiving a single vaccination is thought to involve a primarily cell-mediated, IFN-gamma-dependent mechanism, while humoral immunity has been shown to contribute to challenge rejection in multiply (three times) immunized mice. To better understand the respective contribution of the B lymphocyte- and IFN-gamma-dependent effector arms in host resistance, we compared vaccine-induced immunity in B cell-deficient (muMT) and IFN-gamma knockout (GKO) animals. Unexpectedly, after a single vaccination, B cell knockout (KO) mice displayed reduced protection against challenge infection, although they developed a normal IFN-gamma-dominated cytokine response. This defect in resistance was equivalent to that displayed by GKO animals. Moreover, whereas two additional vaccinations significantly increased the level of immunity in wild-type mice, the protection in B cell KO animals remained unchanged. In contrast, multiple vaccination resulted in increased but, nevertheless, defective resistance in GKO mice. Since FcR gamma KO mice, which lack functional FcgammaRI, FcgammaRIII, and FcepsilonRI, show no defects in vaccine-induced resistance after immunization either one or three times, the B cell-dependent mechanism of protection involved does not appear to require FcR signaling. Together, these findings indicate that effective vaccination against schistosomes depends on the simultaneous induction of both humoral and cell-mediated immunity, a conclusion that may explain the limited success of most subunit vaccine protocols designed to preferentially induce either B cell- or IFN-gamma-dependent protective mechanisms.

IL-13 is a key regulatory cytokine for Th2 cell-mediated pulmonary granuloma formation and IgE responses induced by Schistosoma mansoni eggs.

Schistosoma mansoni egg-induced pulmonary granuloma formation is a cell-mediated inflammatory response associated with dominant Th2-type cytokine expression, tissue eosinophilia, and high levels of serum IgE. In the present study, we show that in vivo blockade of the Th2 cytokine IL-13, using soluble IL-13R alpha2-Fc fusion protein, significantly reduced the size of pulmonary granulomas in unsensitized as well as egg-sensitized mice. Blocking IL-13 also significantly reduced total serum IgE levels. Interestingly, however, IL-13 blockade did not affect the evolving egg-induced Th2-type cytokine response. IL-4, IL-5, as well as IL-13 responses were indistinguishable in control-Fc- and soluble IL-13R alpha2-Fc fusion protein-treated animals. The smaller granulomas were also phenotypically like the control Fc-treated mice, displaying a similar eosinophil content. Additional studies in IL-4-deficient mice demonstrated that IL-13 was produced, but at much lower levels than in wild-type mice, while IL-4 expression was completely independent of IL-13. Moreover, while granuloma formation was partially reduced in IL-4-deficient mice, blocking IL-13 in these animals almost completely abrogated granuloma development and the pulmonary eosinophilia, while it simultaneously increased IFN-gamma production. Together, these data demonstrate that IL-13 serves as an important mediator of Th2-mediated inflammation and plays a role in eliciting IgE responses triggered by schistosome eggs.