Regulation of hepatic fibrosis and extracellular matrix genes by the th response: new insight into the role of tissue inhibitors of matrix metalloproteinases.

Hepatic fibrosis is the hallmark of Schistosoma mansoni infection and often results in portal hypertension and bleeding from esophageal varices. The fibrotic process is highly dependent on type 2 cytokines, yet their role in the regulation of extracellular matrix remodeling genes remains largely unknown. Here, we examined the expression of matrix metalloproteases (MMP) -2, -3, -9, -12, and -13 and their inhibitors, tissue inhibitor of metalloproteases (TIMP) -1, -2, and -3, in the livers of infected mice and correlated their expression profiles with fibrosis and type 2 cytokine production. Expression of MMP-2, -3, -9, -12, and -13 and of TIMP-1 and -2 mRNA rapidly increased at the onset of egg laying in infected mice, while TIMP-3 was unchanged. Because TIMP are presumed to be important regulators of the extracellular matrix, and their expression correlated with the development of fibrosis, we studied their role in fibrogenesis by infecting TIMP-1- and TIMP-2-deficient mice. Strikingly, our data revealed no role for TIMP-1 or -2 in the fibrotic pathology induced by S. mansoni eggs. Because of these findings, we infected IL-10/IFN-gamma-deficient mice that develop an exaggerated fibrotic response to determine whether changes in type 2 cytokine dominance influence the pattern of MMP and TIMP expression. Fibrosis and type 2 cytokine production correlated with increased MMP-2/MMP-9 vs TIMP-1/TIMP-2 expression. These data, in addition to our knockout studies, demonstrate that TIMP-1/TIMP-2 play no essential role in fibrogenesis in schistosomiasis. Indeed, our findings suggest that inhibiting profibrotic cytokines or specific MMP may be a more effective strategy to ameliorate fibrotic pathology.

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.

Mutation of Tec family kinases alters T helper cell differentiation.

The Tec kinases Rlk and Itk are critical for full T cell receptor (TCR)-induced activation of phospholipase C-gamma and mitogen-activated protein kinase. We show here that the mutation of Rlk and Itk impaired activation of the transcription factors NFAT and AP-1 and production of both T helper type 1 (TH1) and TH2 cytokines. Consistent with these biochemical defects, Itk-/- mice did not generate effective TH2 responses when challenged with Schistosoma mansoni eggs. Paradoxically, the more severely impaired Rlk-/-Itk-/- mice were able to mount a TH2 response and produced TH2 cytokines in response to this challenge. In addition, Rlk-/-Itk-/- cells showed impaired TCR-induced repression of the TH2-inducing transcription factor GATA-3, suggesting a potential mechanism for TH2 development in these hyporesponsive cells. Thus, mutations that affect Tec kinases lead to complex alterations in CD4+ TH cell differentiation.

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.

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.

Studies of murine schistosomiasis reveal interleukin-13 blockade as a treatment for established and progressive liver fibrosis.

In several allergic, autoimmune, and infectious diseases, fibrosis is a major cause of morbidity and mortality. Here, using a model of infection-induced liver fibrosis, we show that interleukin (IL)-13 is required at all stages of Schistosomiasis mansoni infection to induce fibrosis. IL-4 production was preserved in IL-13-deficient mice, yet failed to significantly contribute to the fibrotic response in either acute or chronic infection. Significant fibrosis develops in all infected mice, although the magnitude of the response varies widely in inbred mice. C3H/HeN, BALB/c, and C57BL/6 mice develop high, intermediate, and low levels of fibrosis, respectively. Despite these differences, IL-13 antagonism resulted in a marked amelioration of fibrosis in all strains. The fibrotic mechanism in the high- and low-responder strains was unrelated to their tissue eosinophil or mast cell responses, but did correlate with their patterns of IL-13, IL-10, and interferon gamma (IFN-gamma) mRNA expression. Indeed, severe fibrosis correlated with a high IL-13 and low IFN-gamma/IL-10 mRNA response. Because fibrotic diseases are typically progressive disorders, an important issue was to determine whether IL-13 inactivation might be used to treat an established and ongoing fibrotic disease. Here, IL-13 antagonism was highly efficacious, even after fibrosis and the Th2 cytokine response were firmly established. These studies demonstrate the central role played by IL-13 in fibrogenesis and suggest that therapeutic approaches aimed at disrupting the IL-13 pathway will be highly effective at preventing fibrotic disease caused by chronic Th2-mediated inflammatory reactions.

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.

Testing time-, ignorance-, and danger-based models of tolerance.

In this study, we present data showing that tolerance to Ags in the periphery is not determined by the time at which the Ag appears, or by special properties of tissues in newborn mice or newly developing immune systems. We placed male grafts onto immunoincompetent female mice, allowed the grafts to heal for up to 5 mo, and then repopulated the recipients with fetal liver stem cells. We found that the newly arising T cells were neither tolerant nor ignorant of the grafts, but promptly rejected them, though they did not reject female grafts, nor show any signs of autoimmunity. We also found that the H-Y Ag was continuously cross-presented on host APCs, that this presentation was immunogenic, not tolerogenic, and that it depended on the continuous presence of the graft. In searching for the stimulus that might activate the host APCs, we analyzed mRNA expression with a highly sensitive real-time quantitative PCR assay. By using two different "housekeeping" molecules for comparison, we analyzed the message levels for several stress and/or inflammatory molecules in the healed grafts. We found that the long-healed grafts were not equivalent to "normal" skin because the healed grafts expressed lower levels of GAPDH. Altogether, these data suggest that acceptance vs rejection of peripheral tissues is not attributable to ignorance, timing-based tolerance, or special circulation properties of naive T cells in neonatal tissues. It is more likely attributable to an aspect of the context of Ag presentation that remains to be identified.

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.

Studies with double cytokine-deficient mice reveal that highly polarized Th1- and Th2-type cytokine and antibody responses contribute equally to vaccine-induced immunity to Schistosoma mansoni.

A fundamental obstacle to vaccine development in schistosomiasis mansoni is a lack of understanding of what type of an immune response should be invoked. We have addressed this central issue by using the radiation-attenuated cercariae vaccine in mice genetically engineered to exhibit highly polarized type 1 (IL-10/IL-4-deficient) or type 2 (IL-10/IL-12-deficient) cytokine and Ab phenotypes. Our data show that while significant differences in immunity exist after a single vaccination with irradiated cercariae in double cytokine-deficient vs wild-type mice, these differences disappear after two vaccinations. The most important finding of these studies, however, was revealed in vaccinated IL-10-deficient mice. These mice developed a mixed and elevated type 1- and type 2-associated immune response and developed anti-schistosome immunity at levels equal to or better than those in wild-type mice. This immunity in IL-10-deficient mice correlated with higher parasite-specific Ab titers, greater proliferative capacity of lymphocytes, increased frequency of IFN-gamma- and IL-4-secreting cells, elevated perivascular/peribronchial inflammatory responses in the lung, and greater in vitro schistosomulacidal capacity of parasite Ag-elicited cells. These results suggest that optimal vaccine-induced immunity against schistosomes is linked not to the development of a highly polarized response, but, rather, to the induction of both type 1- and type 2-associated immune responses.

Schistosome-infected IL-4 receptor knockout (KO) mice, in contrast to IL-4 KO mice, fail to develop granulomatous pathology while maintaining the same lymphokine expression profile.

Th2 lymphocytes have been postulated to play a major role in the immunopathology induced by Schistosoma mansoni infection. Nevertheless, infected IL-4 knockout (KO) and wild-type (wt) mice develop egg granulomas comparable in size. To further investigate the function of the Th2 response in egg pathology we studied IL-4Ralpha-deficient mice, which are nonresponsive to both IL-4 and IL-13. In striking contrast to IL-4 KO animals, infected IL-4Ralpha KO mice developed only minimal hepatic granulomas and fibrosis despite the presence of CD3+ T cells in the residual egg lesions. Moreover, liver lymphokine mRNA levels in these animals and IL-4 KO mice were equivalent. In addition, infected IL-4Ralpha-deficient, IL-4-deficient, and wt animals developed similar egg Ag-specific IgG Ab titers, arguing that CD4-dependent Th activity is intact in KO mice. As expected, IFN-gamma secretion was strongly up-regulated in mesenteric lymph node cultures from both groups of deficient animals, a change reflected in increased serum IgG2a and IgG2b Ab levels. Surprisingly, Th2 cytokine production in infected IL-4Ralpha KO mice was not abolished but was only reduced and resembled that previously documented in IL-4 KO animals. This residual Th2 response is likely to explain the ability of IL-4 KO mice to generate egg granulomas, which cannot be formed in IL-4Ralpha-deficient animals because of their lack of responsiveness to the same cytokine ligands. Taken together, these findings argue that tissue pathology in schistosomiasis requires, in addition to egg-specific CD4+ lymphocytes, a previously unrecognized IL-4Ralpha+ non-T cell effector population.

Interleukin 5 (IL-5) is not required for expression of a Th2 response or host resistance mechanisms during murine schistosomiasis mansoni but does play a role in development of IL-4-producing non-T, non-B cells.

During schistosomiasis, interleukin-5 (IL-5)-dependent eosinophil responses have been implicated in immunopathology, resistance to superinfection, synergistic interactions with chemotherapeutic agents, and the inductive phase of the egg-induced Th2 response. We examined these issues in IL-5-deficient (IL-5(-/-)) mice. IL-5(-/-) and wild-type (WT) mice were indistinguishable in terms of susceptibility to primary infections and the ability to resist secondary infections. Moreover, hepatic pathology was similar in both strains apart from a relative lack of eosinophils and, during chronic infection, a significantly larger mast cell component in the granulomas of IL-5(-/-) mice. Splenocyte cytokine production in response to soluble egg antigen (SEA) or anti-CD3 revealed no significant differences except for heightened tumor necrosis factor alpha production by cells from chronically infected IL-5(-/-) mice compared to WT animals. In contrast, ionomycin-stimulated non-B, non-T (NBNT) cells from IL-5(-/-) mice produced significantly smaller IL-4 amounts than did NBNT cells from WT animals. This difference was not apparent following plate-bound anti-immunoglobulin E or SEA stimulation. The absence of IL-5 failed to affect the induction of Th2 responses in naive mice. Peritoneal exudate cells recovered from egg-injected IL-5(-/-) or WT mice produced equivalent levels of IL-4 following restimulation with SEA or anti-CD3.

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.

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.