Correction: Interleukin-22-deficiency and microbiota contribute to the exacerbation of Toxoplasma gondii-induced intestinal inflammation

The original version of this Article omitted the author Dr Mathias Chamaillard from the l'Institut de Pasteur, Lille, France. This has been corrected in both the PDF and HTML versions of the Article.

Interleukin-22-deficiency and microbiota contribute to the exacerbation of Toxoplasma gondii-induced intestinal inflammation

Upon oral infection with Toxoplasma gondii cysts (76 K strain) tachyzoites are released into the intestinal lumen and cross the epithelial barrier causing damage and acute intestinal inflammation in C57BL/6 (B6) mice. Here we investigated the role of microbiota and IL-22 in T.gondii-induced small intestinal inflammation. Oral T.gondii infection in B6 mice causes inflammation with IFNγ and IL-22 production. In IL-22-deficient mice, T.gondii infection augments the Th1 driven inflammation. Deficiency in either IL-22bp, the soluble IL-22 receptor or Reg3γ, an IL-22-dependent antimicrobial lectin/peptide, did not reduce inflammation. Under germ-free conditions, T.gondii-induced inflammation was reduced in correlation with parasite load. But intestinal inflammation is still present in germ-free mice, at low level, in the lamina propria, independently of IL-22 expression. Exacerbated intestinal inflammation driven by absence of IL-22 appears to be independent of IL-22 deficiency associated-dysbiosis as similar inflammation was observed after fecal transplantation of IL-22-/- or WT microbiota to germ-free-WT mice. Our results suggest cooperation between parasite and intestinal microbiota in small intestine inflammation development and endogenous IL-22 seems to exert a protective role independently of its effect on the microbiota. In conclusion, IL-22 participates in T.gondii induced acute small intestinal inflammation independently of microbiota and Reg3γ.

IL-22-induced antimicrobial peptides are key determinants of mucosal vaccine-induced protection against H. pylori in mice

Despite the recent description of the mucosal vaccine-induced reduction of Helicobacter pylori natural infection in a phase 3 clinical trial, the absence of immune correlates of protection slows the final development of the vaccine. In this study, we evaluated the role of interleukin (IL)-22 in mucosal vaccine-induced protection. Gastric IL-22 levels were increased in mice intranasally immunized with urease+cholera toxin and challenged with H. felis, as compared with controls. Flow cytometry analysis showed that a peak of CD4+IL-22+IL-17+ T cells infiltrating the gastric mucosa occurred in immunized mice in contrast to control mice. The inhibition of the IL-22 biological activity prevented the vaccine-induced reduction of H. pylori infection. Remarkably, anti-microbial peptides (AMPs) extracted from the stomachs of vaccinated mice, but not from the stomachs of non-immunized or immunized mice, injected with anti-IL-22 antibodies efficiently killed H. pylori in vitro. Finally, H. pylori infection in vaccinated RegIIIβ-deficient mice was not reduced as efficiently as in wild-type mice. These results demonstrate that IL-22 has a critical role in vaccine-induced protection, by promoting the expression of AMPs, such as RegIIIβ, capable of killing Helicobacter. Therefore, it can be concluded that urease-specific memory Th17/Th22 cells could constitute immune correlates of vaccine protection in humans.

Interleukin-22 regulates antimicrobial peptide expression and keratinocyte differentiation to control Staphylococcus aureus colonization of the nasal mucosa

The local immune response occurring during Staphylococcus aureus nasal colonization remains ill-defined. Studies have highlighted the importance of T-cell immunity in controlling S. aureus colonization of the nasal mucosa. We extend these observations, identifying a critical role for interleukin (IL)-22 in this process. IL-22 is basally expressed within the nasal mucosa and is induced upon S. aureus colonization. IL-22 is produced by CD4+ and CD8+ T lymphocytes at this site, with innate-like lymphocytes also contributing. IL-22-/- mice demonstrate significantly elevated levels of S. aureus nasal colonization as compared with wild-type (WT) mice. This was associated with reduced expression of antimicrobial peptides (AMPs) in the nose. Furthermore, expression of staphylococcal ligands loricrin and cytokeratin 10 was higher in the noses of IL-22-/- as compared with WT mice. IL-17 has been shown to regulate S. aureus nasal colonization by controlling local neutrophil responses; however, IL-17 expression and neutrophil responses were comparable in the noses of IL-22-/- and WT mice during S. aureus colonization. We conclude that IL-22 has an important role in controlling S. aureus nasal colonization through distinct mechanisms, with IL-22 mediating its effect exclusively by inducing AMP expression and controlling availability of staphylococcal ligands.

Donor interleukin-22 and host type I interferon signaling pathway participate in intestinal graft-versus-host disease via STAT1 activation and CXCL10

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation, limiting the success of this therapy. We previously reported that interleukin-22 (IL-22) participates to aGVHD development, but the underlying mechanisms of its contribution remain poorly understood. In this study, we analyzed the mechanism of the pathological function of IL-22 in intestinal aGVHD. Ex-vivo colon culture experiments indicated that IL-22 was able to induce Th1-like inflammation via signal transducer and activator of transcription factor-1 (STAT1) and CXCL10 induction in the presence of type I interferon (IFN). To evaluate a potential synergy between IL-22 and type I IFN in aGVHD, we transplanted recipient mice, either wild-type (WT) or type I IFN receptor deficient (IFNAR(-/-)), with bone marrow cells and WT or IL-22 deficient (IL-22(-/-)) T cells. We observed a decreased GVHD severity in IFNAR(-/-) recipient of IL-22(-/-) T cells, which was associated with a lower level of STAT1 activation and reduced CXCL10 expression in the large intestine. Finally, immunohistochemistry staining of STAT1 performed on gastrointestinal biopsies of 20 transplanted patients showed exacerbated STAT1 activation in gastrointestinal tissues of patients with aGVHD as compared with those without aGVHD. Thus, interfering with both IL-22 and type I IFN signaling may provide a novel approach to limit aGVHD.

IL-22BP is produced by eosinophils in human gut and blocks IL-22 protective actions during colitis

Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel diseases (IBDs), are characterized by high levels of IL-22 production. Rodent studies revealed that this cytokine is protective during colitis but whether this is true in IBDs is unclear. We show here that levels of the soluble inhibitor of IL-22, interleukin 22-binding protein (IL-22BP), are significantly enhanced during IBDs owing to increased numbers of IL-22BP-producing eosinophils, that we unexpectedly identify as the most abundant source of IL-22BP protein in human gut. In addition, using IL-22BP-deficient rats, we confirm that endogenous IL-22BP is effective at blocking protective actions of IL-22 during acute colitis. In conclusion, our study provides new important insights regarding the biology of IL-22 and IL-22BP in the gut and indicates that protective actions of IL-22 are likely to be suboptimal in IBDs thus making IL-22BP a new relevant therapeutic target.

IL-22 deficiency in donor T cells attenuates murine acute graft-versus-host disease mortality while sparing the graft-versus-leukemia effect

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation (allo-HCT), limiting the success of this therapy. Many proinflammatory cytokines secreted following the conditioning regimen have been linked to aGVHD initiation. Interleukin-22 (IL-22) is a cytokine related to IL-10 for its structure and is secreted by T helper type 17 (TH17) cells and innate immune cells. Given the paradoxical role of IL-22 in inflammation with both protective or proinflammatory functions, we investigated whether IL-22 could have a role in aGVHD pathophysiology in a mouse allo-HCT model. In this study, we show that IL-22 deficiency in donor T cells can decrease the severity of aGVHD, while limiting systemic and local inflammation in aGVHD target organs. In addition, we found that Foxp3+ regulatory T cells (Treg cells) were increased in recipient mice that received IL-22-deficient T cells, suggesting that Treg were involved in the reduced severity of GVHD. Finally, we found that the graft-versus-leukemia (GVL) effect mediated by donor T cells was preserved in the absence of IL-22. Overall, these data suggest that targeting of IL-22 may represent a valid approach towards decreasing aGVHD severity after allo-HCT while preserving the GVL effect.

Antibody production by injection of living cells expressing non self antigens as cell surface type II transmembrane fusion protein

Antigen expression and purification are laborious, time consuming and frequently difficult steps in the process of antibody production. In the present study, we developed a method avoiding these two steps. This method relies on the injection of histocompatible living cells stably expressing the antigen as a cell surface type II transmembrane fusion protein. A vector, nicknamed pCD1-CD134L, was constructed to express the antigen fused at the carboxyterminal end of the human CD134 ligand (CD134L) type II transmembrane protein on the surface of eucaryotic cells. This vector was shown to induce cell surface expression of epitopes from human c-Myc (soluble protein), uterogloblin-related protein 1 (secreted protein) and CD94 (type II transmembrane protein). Using this vector, we developed a method to produce antibodies without antigen production. The flowchart of this method is as follows: (i) cloning of the antigen in the pCD1-CD134L vector; (ii) production of a histocompatible cell line stably expressing the CD134L-antigen fusion protein; (iii) testing for cell surface expression of the fusion protein by targeting the CD134L carrier; and (iv) prime-boost immunisation with living cells expressing the fusion protein. This method was successfully used for production of polyclonal antibodies raised against Ixodes ricinus calreticulin (secreted protein) in mice and for production of monoclonal antibodies raised against an epitope of Vaccinia virus A56 (type I transmembrane protein) protein in rat. The present study is the first to demonstrate the use of a type II transmembrane protein as a carrier for cell surface display of antigens.

IL-22 defines a novel immune pathway of antifungal resistance

The role of IL-17 and Th17 cells in immunity vs. pathology associated with the human commensal Candida albicans remains controversial. Both positive and negative effects on immune resistance have been attributed to IL-17/Th17 in experimental candidiasis. In this study, we provide evidence that IL-22, which is also produced by Th17 cells, has a critical, first-line defense in candidiasis by controlling the growth of infecting yeasts as well as by contributing to the host's epithelial integrity in the absence of acquired Th1-type immunity. The two pathways are reciprocally regulated, and IL-22 is upregulated under Th1 deficiency conditions and vice versa. Whereas both IL-17A and F are dispensable for antifungal resistance, IL-22 mediates protection in IL-17RA-deficient mice, in which IL-17A contributes to disease susceptibility. Thus, our findings suggest that protective immunity to candidiasis is made up of a staged response involving an early, IL-22-dominated response followed by Th1/Treg reactivity that will prevent fungal dissemination and supply memory.

Sputum eosinophilia: an early marker of bronchial response to occupational agents

BACKGROUND

False-negative responses to specific inhalation challenge (SIC) with occupational agents may occur. We explored whether assessing changes in sputum cell counts would help improve the identification of bronchial reactivity to occupational agents during SICs.

METHODS

The predictive value of the changes in sputum cell counts after a negative FEV(1) response to a first challenge exposure to an occupational agent was determined using the changes in airway calibre observed during repeated challenges as the 'gold standard'. The study included 68 subjects investigated for work-related asthma in a tertiary centre. After a control day, the subjects were challenged with the suspected occupational agent(s) for up to 2 h. All subjects who did not show an asthmatic reaction were re-challenged on the following day. Additional challenges were proposed to those who demonstrated a > or = 2% increase in sputum eosinophils or an increase in nonspecific bronchial hyperresponsiveness to histamine after the second challenge day.

RESULTS

Six of the 35 subjects without changes in FEV(1) on the first challenge developed an asthmatic reaction on subsequent challenges. ROC analysis revealed that a >3% increase in sputum eosinophils at the end of the first challenge day was the most accurate parameter for predicting the development of an asthmatic response on subsequent challenges with a sensitivity of 67% and a specificity of 97%.

CONCLUSIONS

An increase in sputum eosinophils is an early marker of specific bronchial reactivity to occupational agents, which may help to identify subjects who will develop an asthmatic reaction only after repeated exposure.

IL-9/IL-9 receptor signaling selectively protects cortical neurons against developmental apoptosis

In mammals, programmed cell death (PCD) is a central event during brain development. Trophic factors have been shown to prevent PCD in postmitotic neurons. Similarly, cytokines have neurotrophic effects involving regulation of neuronal survival. Nevertheless, neuronal PCD is only partially understood and host determinants are incompletely defined. The present study provides evidence that the cytokine interleukin-9 (IL-9) and its receptor specifically control PCD of neurons in the murine newborn neocortex. IL-9 antiapoptotic action appeared to be time-restricted to early postnatal stages as both ligand and receptor transcripts were mostly expressed in neocortex between postnatal days 0 and 10. This period corresponds to the physiological peak of apoptosis for postmitotic neurons in mouse neocortex. In vivo studies showed that IL-9/IL-9 receptor pathway inhibits apoptosis in the newborn neocortex. Furthermore, in vitro studies demonstrated that IL-9 and its receptor are mainly expressed in neurons. IL-9 effects were mediated by the activation of the JAK/STAT (janus kinase/signal transducer and activator of transcription) pathway, whereas nuclear factor-kappaB (NF-kappaB) or Erk pathways were not involved in mediating IL-9-induced inhibition of cell death. Finally, IL-9 reduced the expression of the mitochondrial pro-apoptotic factor Bax whereas Bcl-2 level was not significantly affected. Together, these data suggest that IL-9/IL-9 receptor signaling pathway represents a novel endogenous antiapoptotic mechanism for cortical neurons by controlling JAK/STAT and Bax levels.

Interleukin-22 deficiency accelerates the rejection of full major histocompatibility complex-disparate heart allografts

Interleukin-22 (IL-22) was recently described as an effector cytokine produced by TH17 CD4(+) T lymphocytes that, cooperatively with IL-17, mediates IL-23-driven inflammation. Because there was experimental evidence for the role of IL-17 in acute rejection of vascularized allografts, we undertook the present study to assess the function of IL-22 in the process. There was an early transient expression of IL-22 in C57BL/6 mouse cardiac allografts (2-4 days posttransplantation) transplanted to BALB/c recipients. The main source of IL-22 among infiltrating leukocytes was cells expressing the macrophage/monocyte markers Mac3 and CD11b. T cells and granulocytes present in the rejected graft did not express IL-22. Surprisingly, the absence of IL-22 accelerated the rejection of fully histoincompatible hearts. Histology of rejected organs revealed the presence of intensive intragraft thrombosis and disseminated hemorrhagic necrosis. Taken together, these results demonstrated that IL-22 was not an effector lymphokine in cardiac allograft rejection, but early intragraft expression of the cytokine protected it from rejection.

JAK kinases overexpression promotes in vitro cell transformation

Constitutive activation of the JAK-STAT pathway is frequent in cancer and contributes to oncogenesis. Here, we took advantage of the Ba/F3 cell line, a murine proB cell line dependent on IL-3 for growth, to analyse mechanisms of constitutive STAT activation in vitro. Cytokine-independent and tumorigenic Ba/F3 cell lines were derived from a two-step selection process. Cells transfected with a defective IL-9 receptor acquire IL-9 responsiveness during a first step of selection, and progress after a second selection step to autonomously growing tumorigenic cells. Microarray analysis pointed to JAK1 overexpression as a key genetic event in this transformation. Overexpression of JAK1 not only increased the sensitivity to IL-9 but also allowed a second selection step toward cytokine-independent growth with constitutive STAT activation. This progression was dependent on a functional FERM and kinase JAK1 domain. Similar results were observed after JAK2, JAK3 and TYK2 overexpression. All autonomous cell lines showed an activation of STAT5, ERK1-2 and AKT but only TYK2-overexpressing cell lines showed a constitutive activation of STAT3. Thus, JAK overexpression can be considered as one of the oncogenic events leading to the constitutive activation of the JAK-STAT pathway.

IL-9 promotes anti-Mycobacterium leprae cytotoxicity: involvement of IFNgamma

Interleukin 9 (IL-9) is a T-cell derived factor preferentially expressed by CD4+ Th2 cells and it has been characterized both in human and murine systems. It is a pleiotropic cytokine with multiple functions on cells of the lymphoid, myeloid and mast cell lineages, as well as on lung epithelial cells. Other activities described for IL-9 support its contribution to asthma and its important role in helminthic infections, where a Th2 response can be protective and IL-9 enhances resistance or is responsible for elimination of the nematode. Nevertheless, until recently there were no studies on its role in bacterial infections in man. We have demonstrated that cytokines can modulate the specific cytotoxicity generation in peripheral blood mononuclear cells from leprosy patients and normal controls. In the present report we studied the effect of IL-9 in this experimental model. Our results indicate that IL-9 can counteract the negative effect mediated by IL-4 on the generation of M. leprae-induced cytotoxic T lymphocytes. Moreover, it can increase this lytic activity in controls and enhance the stimulatory effect of IL-2 or IL-6 in cells from leprosy patients and controls. IL-9 is also able to revert the inhibitory effect of IL-10 and IL-13 on the M. leprae-induced cytotoxic activity. Although the exact mechanism of action of IL-9 remains to be determined, interferon gamma seems to be required for the effect of IL-9 in this experimental model. These data suggest that IL-9 may have an atypical Th2 behaviour and play a role in the modulation of the immune response to mycobacterial infections.

[Role of interleukin-9 in asthma and allergic reactions]

Interleukin 9 (IL-9) is a cytokine produced by activated T lymphocytes and that activates in vitro mast cells as well as T and B lymphocytes. In vivo, transgenic mice overexpressing the gene encoding IL-9 show several of the hallmarks of human allergic asthma: increased IgE concentration, bronchial mastocytosis, eosinophilia, increased mucus production, as well as bronchial hyperresponsiveness. Whereas some of these features reflect direct IL-9 activities on target cells such as mast cells and B lymphocytes, increased mucus production and eosinophilia rather result from IL-13 and IL-5 production induced by IL-9 in T lymphocytes and mast cells. Preclinical studies in mice have shown that anti-IL-9 blocking antibodies interfere with the development of asthma-like reactions. In the human species, asthmatic patients produce large amounts of this cytokine and IL-9 production correlates nicely with species biological parameters of the disease. Phase 2 clinical trials are in progress to test the efficacy of anti-IL-9 antibodies in humans.

Blockade of Interleukin-12 Function by Protein Vaccination Attenuates Atherosclerosis

Background— Interleukin-12 (IL-12) has been identified as a key inducer of a type 1 T-helper cell cytokine pattern, which is thought to contribute to the development of atherosclerosis. We sought to study the role of IL-12 in atherosclerosis by inhibition of IL-12 using a newly developed vaccination technique that fully blocks the action of IL-12.

Methods and Results— LDL receptor–deficient (LDLr −/− ) mice were vaccinated against IL-12 by 5 intramuscular injections of IL-12–PADRE complex in combination with adjuvant oil-in-water emulsion (low dose)/MPL/QS21 every 2 weeks. Two weeks thereafter, atherogenesis was initiated in the carotid artery by perivascular placement of silicone elastomer collars. IL-12 vaccination resulted in the induction of anti–IL-12 antibodies that functionally blocked the action of IL-12 as determined in an IL-12 bioassay. Blockade of IL-12 by vaccination of LDLr −/− mice resulted in significantly reduced (68.5%; P <0.01) atherogenesis compared with control mice without a change in serum cholesterol levels. IL-12 vaccination also resulted in a significant decrease in intima/media ratios (66.7%; P <0.01) and in the degree of stenosis (57.8%; P <0.01). On IL-12 vaccination, smooth muscle cell and collagen content in the neointima increased 2.8-fold ( P <0.01) and 4.2-fold ( P <0.01), respectively.

Conclusions— Functional blockade of endogenous IL-12 by vaccination resulted in a significant 68.5% reduction in atherogenesis in LDLr −/− mice. Vaccination against IL-12 also improved plaque stability, from which we conclude that the blockade of IL-12 by vaccination may be considered a promising new strategy in the treatment of atherosclerosis.

Oxidative burst in lipopolysaccharide-activated human alveolar macrophages is inhibited by interleukin-9

Interleukin (IL)-9 is known to regulate many cell types involved in T-helper type 2 responses classically associated with asthma, including B- and T-lymphocytes, mast cells, eosinophils and epithelial cells. In contrast, target cells mediating the effects of IL-9 in the lower respiratory tract remain to be identified. Therefore, the authors evaluated the activity of IL-9 on human alveolar macrophages (AM) from healthy volunteers. AM preincubated with IL-9 before lipopolysaccharide (LPS) stimulation exhibited a decreased oxidative burst, as previously shown with IL-4. The inhibitory effect of IL-9 was abolished by anti-hIL-9R alpha monoclonal antibody, and presence of IL-9 receptors on AM was demonstrated by immunofluorescence. Both IL-4 and IL-9 failed to modulate tumour necrosis factor-alpha, IL-8 and IL-10 release by LPS-stimulated AM. However, several observations suggested that IL-9 and IL-4 act through different mechanisms: 1) interferon-gamma antagonised the IL4- but not the IL-9-mediated inhibition of AM oxidative burst; 2) expression of CD14 was downregulated by IL-4 but not by IL-9 and 3) production of tumour growth factor-beta by activated AM was potentiated by IL-9 and not by IL4, and was required for the IL-9-mediated inhibition of AM oxidative burst. These observations provide additional information concerning the activity of interleukin-9 in the lung, related to inflammatory or fibrosing lung processes.

Crystallization and synchrotron X-ray diffraction studies of human interleukin-22

Human interleukin-22, a novel member of the cytokine family, has been crystallized in hanging drops using the vapour-diffusion technique. Preliminary X-ray diffraction experiments using synchrotron radiation reveal that the protein crystallizes in space group P2(1)2(1)2(1), with unit-cell parameters a = 55.44, b = 61.62, c = 73.43 A, and diffracts beyond 2.00 A resolution.

Cutting edge: STAT activation by IL-19, IL-20 and mda-7 through IL-20 receptor complexes of two types

IL-10-related cytokines include IL-20 and IL-22, which induce, respectively, keratinocyte proliferation and acute phase production by hepatocytes, as well as IL-19, melanoma differentiation-associated gene 7, and AK155, three cytokines for which no activity nor receptor complex has been described thus far. Here, we show that mda-7 and IL-19 bind to the previously described IL-20R complex, composed by cytokine receptor family 2-8/IL-20Ralpha and DIRS1/IL-20Rbeta (type I IL-20R). In addition, mda-7 and IL-20, but not IL-19, bind to another receptor complex, composed by IL-22R and DIRS1/IL20Rbeta (type II IL-20R). In both cases, binding of the ligands results in STAT3 phosphorylation and activation of a minimal promoter including STAT-binding sites. Taken together, these results demonstrate that: 1) IL-20 induces STAT activation through IL-20R complexes of two types; 2) mda-7 and IL-20 redundantly signal through both complexes; and 3) IL-19 signals only through the type I IL-20R complex.

Effects of normothermia versus hypothermia on extravascular lung water and serum cytokines during cardiopulmonary bypass: a randomized, controlled trial

OBJECTIVE

To evaluate the influence of perfusion temperature on the systemic effects of cardiopulmonary bypass (CPB), including extravascular lung water index (EVLWI), and serum cytokines.

DESIGN

Prospective, randomized, controlled study.

SETTING

Cardiothoracic intensive care unit of a university hospital.

PATIENTS

Patients undergoing elective coronary artery bypass grafting.

INTERVENTIONS

Twenty-one patients undergoing elective coronary artery bypass grafting were randomly assigned to receive either normothermic bypass (36 degrees C, n = 8) with intermittent antegrade warm blood cardioplegia (IAWBC), or hypothermic (32 degrees C, n = 13) CPB with cold crystalloid cardioplegia.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, heart rate, cardiac output, systemic vascular resistance, mean pulmonary arterial pressure, and pulmonary vascular resistance were determined at baseline, i.e., after induction of anesthesia but before sternal opening (T-1), at arrival in the intensive care unit (T0), and 4 hrs (T4), 8 hrs (T8), and 24 hrs (T24) after surgery. EVLWI, intrathoracic blood volume index (ITBVI), and EVLW/ITBV ratio were obtained by using thermal dye dilution utilizing an arterial thermistor-tipped fiberoptic catheter and were recorded at T-1, T0, T4, T8, and T24. Serial blood samples for cytokine measurements were obtained at each hemodynamic measurement time point. Before, during, and after CPB, there were no differences in the conventional hemodynamic measurements between the groups. There were no changes in EVLWI up to T8 in either group. Furthermore, no change in the ratio EVLW/ITBW was observed between the groups at any time, further indicating the absence of a change in pulmonary permeability. Plasma levels of interleukin-6, tumor necrosis factor-alpha, and interleukin-10 increased during and after CPB, independently of the perfusion temperature.

CONCLUSION

Normothermic CPB is not associated with additional inflammatory and related systemic adverse effects regarding cytokine production and EVLWI as compared with mild hypothermia. The potential temperature-dependent release of cytokines and subsequent inflammation has not been observed and normothermic CPB may be seen as a safe technique regarding this issue.

New insights into the role of cytokines in asthma

Asthma is a triad of intermittent airway obstruction, bronchial smooth muscle cell hyperreactivity to bronchoconstrictors, and chronic bronchial inflammation. From an aetiological standpoint, asthma is a heterogeneous disease, but often appears as a form of immediate hypersensitivity. Many patients with asthma have other manifestations of atopy, such as rhinitis or eczema. Even among non-atopic patients with asthma, the pathophysiology of airway constriction is similar, raising the hypothesis that alternative mechanisms of mast cell degranulation may underlie the disease. The primary inflammatory lesion of asthma consists of accumulation of CD4(+) T helper type 2 (TH2) lymphocytes and eosinophils in the airway mucosa. TH2 cells orchestrate the asthmatic inflammation through the secretion of a series of cytokines, particularly interleukin 4 (IL-4), IL-13, IL-5, and IL-9. IL-4 is the major factor regulating IgE production by B cells, and is required for optimal TH2 differentiation. However, blocking IL-4 is not sufficient to inhibit the development of asthma in experimental models. In contrast, inhibition of IL-13, another TH2 cytokine whose signal transduction pathway overlaps with that of IL-4, completely blocks airway hyperreactivity in mouse asthma models. IL-5 is a key factor for eosinophilia and could therefore be responsible for some of the tissue damage seen in chronic asthma. IL-9 has pleiotropic activities on allergic mediators such as mast cells, eosinophils, B cells and epithelial cells, and might be a good target for therapeutic interventions. Finally, chemokines, which can be produced by many cell types from inflamed lungs, play a major role in recruiting the mediators of asthmatic inflammation. Genetic studies have demonstrated that multiple genes are involved in asthma. Several genome wide screens point to chromosome 5q31--33 as a major susceptibility locus for asthma and high IgE values. This region includes a cluster of cytokine genes, and genes encoding IL-3, IL-4, IL-5, IL-9, IL-13, granulocyte macrophage colony stimulating factor, and the beta chain of IL-12. Interestingly, for some of these cytokines, a linkage was also established between asthma and their receptor. Another susceptibility locus has been mapped on chromosome 12 in a region that contains other potential candidate cytokine genes, including the gene encoding interferon gamma, the prototypical TH1 cytokine with inhibitory activities for TH2 lymphocytes. Taken together, both experimental and genetic studies point to TH2 cytokines, such as IL-4, IL-13, IL-5, and IL-9, as important targets for therapeutic applications in patients with asthma.

Deleterious effects of IL-9-activated mast cells and neuroprotection by antihistamine drugs in the developing mouse brain

Elevated mean IL-9 serum levels have been observed in human neonates who will later develop cerebral palsy. In earlier studies, using a newborn mouse model of excitotoxic lesions mimicking those described in human cerebral palsy, we found that IL-9 pretreatment exacerbated brain damage produced by intracerebral injections of the glutamatergic analog ibotenate. Among its different cell targets, the Th2 cytokine IL-9 is a mast cell growth and differentiation factor that can cause mast cells to release various substances including histamine. In the present study, we sought to determine whether the deleterious effects of IL-9 in our mouse model were mediated by mast cells through histamine release. All mouse pups were pretreated with intraperitoneal injections of IL-9 or saline between postnatal days (P) P1 and P5. Immunohistochemistry for murine mast cell protease-1 performed on P5 showed an increased density of labeled cells in the neopallium of IL-9-treated Swiss pups as compared with controls. Western blot analysis confirmed the increased murine mast cell protease-1 brain content of IL-9-treated Swiss mice. IL-9 pretreatment had no significant effect on ibotenate-induced excitotoxic brain lesions in mast cell-deficient P5 pups (WBB6F1/J kit(W/W-v)), whereas IL-9 exacerbated these lesions in the control littermates with normal mast cell populations. Finally, cromoglycate or antihistamine drugs significantly reduced ibotenate-induced brain lesions in IL-9-treated Swiss pups. Taken together, these data suggest that recruitment of cerebral mast cells with histamine release may contribute to the exacerbation of neonatal excitotoxic brain lesions produced by IL-9. Neuroprotective strategies targeting mast cells may be useful in some neonates at risk for cerebral palsy.

Cloning and characterization of IL-22 binding protein, a natural antagonist of IL-10-related T cell-derived inducible factor/IL-22

The class II cytokine receptor family includes the receptors for IFN-alphabeta, IFN-gamma, IL-10, and IL-10-related T cell-derived inducible factor/IL-22. By screening genomic DNA databases, we identified a gene encoding a protein of 231 aa, showing 33 and 34% amino acid identity with the extracellular domains of the IL-22 receptor and of the IL-20R/cytokine receptor family 2-8, respectively, but lacking the transmembrane and cytoplasmic domains. A lower but significant sequence identity was found with other members of this family such as the IL-10R (29%), cytokine receptor family 2-4/IL-10Rbeta (30%), tissue factor (26%), and the four IFN receptor chains (23-25%). This gene is located on chromosome 6q24, at 35 kb from the IFNGR1 gene, and is expressed in various tissues with maximal expression in breast, lungs, and colon. The recombinant protein was found to bind IL-10-related T cell-derived inducible factor/IL-22, and to inhibit the activity of this cytokine on hepatocytes and intestinal epithelial cells. We propose to name this natural cytokine antagonist IL-22BP for IL-22 binding protein.

Interleukin-9 reduces lung fibrosis and type 2 immune polarization induced by silica particles in a murine model

We examined the effect of interleukin (IL)-9, a cytokine active on B and T lymphocytes and associated with bronchial asthma, on the development of lung fibrosis induced by crystalline silica particles. Therefore, we compared the response to silica (1 and 5 mg/animal, intratracheally) in transgenic mice that constitutively express high levels of IL-9 (Tg5) and their wild-type counterparts (FVB). At 2 and 4 mo after treatment with silica, histologic examination and measurement of lung hydroxyproline content showed that the severity of fibrosis was significantly less important in Tg5 mice than in their wild-type counterparts. Intraperitoneal injection of IL-9 in C57BL/6 mice also reduced the amplitude of silica-induced lung fibrosis. The reduction of lung fibrosis by IL-9 was associated with a significant expansion of the B-lymphocyte population, both in bronchoalveolar lavage (BAL) and in the pulmonary parenchyma. In wild-type animals, silica-induced fibrosis correlated with markers of a T helper 2-like response such as upregulation of IL-4 levels in lung tissue and an increased immunoglobulin (Ig) G1/IgG2a ratio in BAL. Immunohistochemical studies demonstrated that the upregulation of IL-4 associated with the development of fibrosis was mainly localized in inflammatory alveolar macrophages. In transgenic mice, the level of IL-4 in lung homogenates was not significantly affected by silica treatment, and a reduced IgG1/IgG2a ratio was observed upon treatment with silica. The levels of interferon-gamma were significantly decreased after silica treatment in both strains. Together, these observations point to an antifibrotic effect of IL-9 in pulmonary fibrosis associated with a limitation of the type 2 polarization which accompanies lung fibrosis.

Interleukin-9 induces 24P3 lipocalin gene expression in murine T cell lymphomas

Interleukin-9 (IL-9) is a Th2 cytokine whose overexpression is associated with asthma and T cell lymphomagenesis. All the IL-9 activities studied so far are mediated by a specific hemopoietin receptor that activates a Jak/STAT pathway. Searching for genes specifically modulated by IL-9, we observed that the 24P3 mRNA is strongly upregulated in BW5147 T lymphoma cells upon IL-9 stimulation. 24P3 is a member of the lipocalin family, and has been reported to bind N-formyl-Met-Leu-Phe, a potent neutrophil chemoattractant, and possibly other lipophilic mediators of inflammation. A similar 24P3 induction was observed in other T cell lymphomas (EL4 and TH201) in response to IL-9, as well as in EL4 cells stimulated with IL-6 or IL-1. By contrast, other IL-9-responsive cells such as mast cell line MC9 and B cell lymphoma A20 showed no 24P3 induction upon IL-9 stimulation. Experiments using IL-9R mutants indicated that STAT transcription factors, particularly STAT3, are involved in this process. However, 24P3 gene induction was slow, reaching a plateau from 36 to 72 hours after stimulation and was inhibited if cells were treated with cycloheximide during the first 8 hours of IL-9 stimulation, suggesting an indirect induction requiring new protein synthesis.

Interleukin-9 (IL-9) induces cell growth arrest associated with sustained signal transducer and activator of transcription activation in lymphoma cells overexpressing the IL-9 receptor

Murine interleukin (IL)-9 inhibits apoptosis in murine T lymphomas via signal transducer and activator of transcription (STAT) factors. After transfection of the human IL-9 receptor, human IL-9 had a similar antiapoptotic activity, but, unlike the mouse protein, inhibited proliferation. This effect was correlated with the level of receptor expression and the extent of STAT phosphorylation. Expression of a moderate level of suppressor of cytokine signaling 3 (SOCS3) reduced STAT activation by human IL-9 and prevented inhibition of growth but not of apoptosis. Using mutated IL-9 receptors, we showed that inhibition of proliferation was correlated with STAT1 and STAT3 activation by IL-9 and induction of the cell cycle inhibitor p19/ink4d, a STAT3 target gene. Activation of STAT1 by IFN-gamma did not result in cell growth arrest. In this model, cell growth inhibition is therefore associated with a higher number of receptors, a more robust STAT activation, and a greater sensitivity to SOCS3 expression, compared to apoptosis inhibition.

Interleukin 9 induces expression of three cytokine signal inhibitors: cytokine-inducible SH2-containing protein, suppressor of cytokine signalling (SOCS)-2 and SOCS-3, but only SOCS-3 overexpression suppresses interleukin 9 signalling

Interleukin 9 (IL-9) is a cytokine preferentially produced by T helper type 2 lymphocytes and active on various cell types such as T- and B-lymphocytes, mast cells and haemopoietic progenitors. The IL-9 receptor (IL-9R) belongs to the haemopoietic receptor superfamily and its signal transduction involves mainly the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. Here we studied the implication of a novel family of suppressors of cytokine signalling (called CIS, for cytokine-inducible SH2-containing protein, and SOCS, for suppressor of cytokine signalling) in IL-9 signal attenuation. In BW5147 T-cell lymphoma, IL-9 induced the rapid expression of CIS, SOCS-2 and SOCS-3 with a peak after 2 h of stimulation. Using IL-9R mutants, we showed that STAT activation is required for CIS/SOCS induction: CIS and SOCS-2 expression was induced either via STAT1 and/or STAT3 or via STAT5 but only STAT1 and/or STAT3 were involved in SOCS-3 expression. The effect of these three proteins on IL-9 signal transduction was assessed by transient transfection in HEK-293 cells expressing the components of the IL-9 signalling pathway and a STAT-responsive reporter construct. These experiments showed that only SOCS-3 is able to inhibit IL-9-induced signal transduction; neither CIS nor SOCS-2 exerted any effect. Stable transfection of CIS and SOCS-3 in BW5147 lymphoma cells showed that only overexpression of SOCS-3 had an inhibitory activity on STAT activation, gene induction and the anti-apoptotic activity of IL-9. By contrast, CIS failed to affect the IL-9 response.

IL-TIF/IL-22: genomic organization and mapping of the human and mouse genes

IL-TIF is a new cytokine originally identified as a gene induced by IL-9 in murine T lymphocytes, and showing 22% amino acid identity with IL-10. Here, we report the sequence and organization of the mouse and human IL-TIF genes, which both consist of 6 exons spreading over approximately 6 Kb. The IL-TIF gene is a single copy gene in humans, and is located on chromosome 12q15, at 90 Kb from the IFN gamma gene, and at 27 Kb from the AK155 gene, which codes for another IL-10-related cytokine. In the mouse, the IL-TIF gene is located on chromosome 10, also in the same region as the IFN gamma gene. Although it is a single copy gene in BALB/c and DBA/2 mice, the IL-TIF gene is duplicated in other strains such as C57Bl/6, FVB and 129. The two copies, which show 98% nucleotide identity in the coding region, were named IL-TIF alpha and IL-TIF beta. Beside single nucleotide variations, they differ by a 658 nucleotide deletion in IL-TIF beta, including the first non-coding exon and 603 nucleotides from the promoter. A DNA fragment corresponding to this deletion was sufficient to confer IL-9-regulated expression of a luciferase reporter plasmid, suggesting that the IL-TIF beta gene is either differentially regulated, or not expressed at all.

Role of insulin receptor substrate-2 in interleukin-9-dependent proliferation

Interleukin-9 (IL-9) stimulation results in JAK, STAT and IRS1/2 phosphorylation. The role of IRS adaptor proteins in IL-9 signaling is not clear. We show that IL-9 induces IRS2 phosphorylation and association with phosphatidylinositol-3 kinase (PI 3-K) p85 subunit in TS1 cells and BaF/9R cells, which proliferate upon IL-9 stimulation. We observed a PI 3-K-dependent phosphorylation of protein kinase B (PKB) in TS1 cells, but not in BaF/9R, nor in other IL-9-dependent cell lines. Finally, 32D cells that were transfected with the IL-9 receptor but lack IRS expression survived in the presence of IL-9. Ectopic IRS1 expression allowed for IL-9-induced proliferation, in the absence of significant PKB phosphorylation.

An animal model for anaplastic large cell lymphoma in the immunocompetent syngeneic C57Bl/6 mouse

We report on the analysis of a murine anaplastic lymphoid cell line TS1G6, established recently by interleukin (IL)-9 transfection. TS1G6 revealed a highly characteristic pattern of large anaplastic cells with mononuclear, binuclear, or multinuclear cells resembling Hodgkin (H) or Sternberg-Reed (SR) cells. This cell line is tumorigenous after injection of as few as 10(4) lymphoma cells into nude or immunocompetent C57Bl/6 mice and leads to death from progressive disease of all treated animals within a few weeks. The histological analysis of these tumors revealed a diffuse large cell malignant lymphoma that is morphologically almost identical to human anaplastic large cell lymphoma (ALCL). The lymphoma cells did not show overexpression of the anaplastic lymphoma kinase (ALK) gene, which is found in about 50% of the cases of human ALCL. Thus, this model may be an animal model for an important subset of human ALCL. The cytokine profile, which is of the T helper 2 type, showed strong parallels to the human lymphoma counterpart. Mice suffering from such lymphomas could not be cured with a regimen using high dose cyclophosphamide similar to many ALCL patients. Such an animal model for ALCL has not yet been recognized, but may provide the basis for investigating new antitumor immunotherapies in a fully immunocompetent host.

Expression of interleukin-9 leads to Th2 cytokine-dominated responses and fatal enteropathy in mice with chronic Schistosoma mansoni infections

Mice infected with Schistosoma mansoni develop Th2 cytokine-mediated granulomatous pathology that is focused on the liver and intestines. In this study, transgenic mice constitutively expressing IL-9 were infected with S. mansoni and the outcome of infection was determined. Eight weeks after infection, transgenic mice with acute infections had a moderate increase in Th2 cytokine production but were overtly normal with respect to parasite infection and pathological responses. Transgenic mice with chronic infections died 10 weeks after infection, with 86% of transgenic mice dead by week 12 of infection, compared to 7% mortality in infected wild-type mice. Stimulation of mesenteric lymph node cells from infected transgenic mice with parasite antigen elicited elevated interleukin-4 (IL-4) and IL-5 production and reduced gamma interferon and tumor necrosis factor alpha production compared to the responses in wild-type mice. Morbid transgenic mice had substantial enlargement of the ileum, which was associated with muscular hypertrophy, mastocytosis, eosinophilia, goblet cell hyperplasia, and increased mucin expression. We also observed that uninfected transgenic mice exhibited alterations in their intestines. Although there was hepatic mastocytosis and eosinophilia in infected transgenic mice, there was no hepatocyte damage. Death of transgenic mice expressing IL-9 during schistosome infection was primarily associated with enteropathy. This study highlights the pleiotropic in vivo activity of IL-9 and demonstrates that an elevated Th2 cytokine phenotype leads to death during murine schistosome infection.

Interleukin-10 blockade corrects impaired in vitro cellular immune responses of systemic lupus erythematosus patients

OBJECTIVE

Many systemic lupus erythematosus (SLE) patients display impaired cellular immune responses against allo- or recall antigens. Given the down-regulating properties of interleukin-10 (IL-10) on antigen-presenting cell functions, this study was undertaken to investigate whether the well-known overproduction of IL-10 by SLE peripheral blood mononuclear cells (PBMC) was involved in this process.

METHODS

We measured the proliferation of SLE or control PBMC against irradiated allogeneic dendritic cells in the absence or presence of antibodies blocking IL-10 activity, or in the absence or presence of IL-12.

RESULTS

As a group, SLE PBMC proliferated against allogeneic targets less than control PBMC. However, SLE patients could be categorized as good responders or poor responders according to the amplitude of their allogeneic response. Interestingly, serum IL-10 concentrations were significantly higher in the poor responders than in the good responders or in the controls, and addition of antibodies blocking IL-10 activity significantly increased the proliferative responses of the group. We confirmed the role of IL-10 in the impaired allogeneic responses displayed by SLE PBMC by demonstrating that addition of IL-10-containing SLE PBMC supernatants inhibited a normal allogeneic response between unrelated healthy controls, and by showing that this inhibitory effect was commensurate with the concentrations of IL-10 measured in the supernatants. In this experimental setting, we also demonstrated that IL-10-containing SLE PBMC supernatants inhibited IL-12 p35 and IL-12 p40 gene expression. Consistent with the last observation, we found that addition of exogenous IL-12 restored the proliferation of poor-responder SLE patients' PBMC.

CONCLUSION

Taken together, these results indicate that dysregulation of the IL-10/IL-12 balance plays a critical role in the impaired cellular immune responses observed in SLE patients.

Human interleukin-10-related T cell-derived inducible factor: molecular cloning and functional characterization as an hepatocyte-stimulating factor

IL-10-related T cell-derived inducible factor (IL-TIF or IL-21) is a new cytokine structurally related to IL-10 and originally identified in the mouse as a gene induced by IL-9 in T cells and mast cells. Here, we report the cloning of the human IL-TIF cDNA, which shares 79% amino acid identity with mouse IL-TIF and 25% identity with human IL-10. Recombinant human IL-TIF was found to activate signal transducer and activator of transcription factors-1 and -3 in several hepatoma cell lines. IL-TIF stimulation of HepG2 human hepatoma cells up-regulated the production of acute phase reactants such as serum amyloid A, alpha1-antichymotrypsin, and haptoglobin. Although IL-10 and IL-TIF have distinct activities, antibodies directed against the beta chain of the IL-10 receptor blocked the induction of acute phase reactants by IL-TIF, indicating that this chain is a common component of the IL-10 and IL-TIF receptors. Similar acute phase reactant induction was observed in mouse liver upon IL-TIF injection, and IL-TIF expression was found to be rapidly increased after lipopolysaccharide (LPS) injection, suggesting that this cytokine contributes to the inflammatory response in vivo.

Cytokine production and killer activity of NK/T-NK cells derived with IL-2, IL-15, or the combination of IL-12 and IL-18

NK cell populations were derived from murine splenocytes stimulated by IL-2, IL-15, or the combination of IL-12 and IL-18. Whereas NK cells derived with the latter cytokines consisted of an homogeneous population of NK cells (DX5+CD3-), those derived with IL-2 or IL-15 belonged to two different populations, namely NK cells (DX5+CD3-) and T-NK cells (DX5+CD3+). Among NK cells, only those derived with IL-12/IL-18 produced detectable levels of cytokines, namely IFN-gamma, IL-10, and IL-13 (with the exception of IL-13 production by NK cells derived with IL-2). As for T-NK cells, IL-2-stimulated cells produced a wide range of cytokines, including IL-4, IL-5, IL-9, IL-10, and IL-13, but no IFN-gamma, whereas IL-15-derived T-NK cells failed to produce any cytokine. Switch-culture experiments indicated that T-NK cells derived in IL-2 and further stimulated with IL-12/IL-18 produced IFN-gamma and higher IL-13 levels. Next, we observed that NK/T-NK cell populations exerted distinct effects on Ig production by autologous splenocytes according to the cytokines with which they were derived. Thus, addition of NK cells derived in IL-12/IL-18 inhibited Ig production and induced strong cytotoxicity against splenocytes, whereas addition of NK or T-NK cells grown in IL-2 or IL-15 did not. Experiments performed in IFN-gammaR knockout mice demonstrated that IFN-gamma was not involved in the killer activity of IL-12/IL-18-derived NK cells. The hypothesis that their cytotoxic activity was related to the induction of target apoptosis was confirmed on murine A20 lymphoma cells. Experiments performed in MRL/lpr mice indicated that IL-12/IL-18-derived NK cells displayed their distinct killer activity through a Fas-independent pathway. Finally, perforin was much more expressed in IL-12/IL-18-derived NK cells as compared with IL-2- or IL-15-derived NK cells, an observation that might explain their unique cytotoxicity.

STAT5 activation is required for interleukin-9-dependent growth and transformation of lymphoid cells

Interleukin-9 (IL-9) is a growth factor for T cells and various hematopoietic and lymphoid tumor cells. IL-9 signaling involves activation of Janus kinase (JAK)1 and JAK3 kinases, and signal transducer and activator of transcription (STAT)1, STAT3 and STAT5. Using a dominant negative form of STAT5 (STAT5delta), we demonstrated that this factor is an important mediator of IL-9-dependent Ba/F3 cell growth. Mutation of the STAT binding site of the IL-9 receptor (tyr116phe) results in an important decrease in STAT activation and inhibition of proliferation in the presence of IL-9. A small number of cells escape this inhibition, and IL-9-dependent cell lines could be derived. The selected cells required activation of STAT5 for growth, which was blocked by STAT5delta expression and enhanced by overexpression of wild-type STAT5. In contrast to parental cells, Ba/F3-Phe116 cells growing in the presence of IL-9 further progress to cytokine-independent tumorigenic clones. These tumorigenic clones exhibited a strong cytokine-independent activation of JAK1 and STAT5, which most likely supports their proliferation. Transfection of a constitutively activated variant of STAT5 promoted the growth of wild-type Ba/F3 cells in the absence of cytokine. Finally, the expression of the proto-oncogene pim-1 was correlated with STAT5 activation and cell growth. Our data suggest that STAT5 is an important mediator of IL-9-driven proliferation and that dysregulation of STAT5 activation favors tumorigenesis of lymphoid cells.

Interleukin-9 upregulates mucus expression in the airways

Interleukin (IL)-9 has recently been shown to play an important role in allergic disease because its expression is strongly associated with the degree of airway responsiveness and the asthmatic-like phenotype. IL-9 is a pleiotropic cytokine that is active on many cell types involved in the allergic immune response. Mucus hypersecretion is a clinical feature of chronic airway diseases; however, the mechanisms underlying the induction of mucin are poorly understood. In this report, we show that IL-9 regulates the expression of a subset of mucin genes in lung cells both in vivo and in vitro. In vivo, the constitutive expression of IL-9 in transgenic mice results in elevated MUC2 and MUC5AC gene expression in airway epithelial cells and periodic acid-Schiff-positive staining (reflecting mucous glycogenates). Similar results were observed in C57BL/6J mice after IL-9 intratracheal instillation. In contrast, instillation of the T helper 1-associated cytokine interferon gamma failed to induce mucin production. In vitro, our studies showed that IL-9 also induces expression of MUC2 and MUC5AC in human primary lung cultures and in the human muccoepidermoid NCI-H292 cell line, indicating a direct effect of IL-9 on inducing mucin expression in these cells. Altogether, these results suggest that upregulation of mucin by IL-9 might contribute to the pathogenesis of human inflammatory airway disorders, such as asthma. These data extend the role of the biologic processes that IL-9 has on regulating the many clinical features of asthma and further supports the IL-9 pathway as a key mediator of the asthmatic response.

Bcl-3 expression promotes cell survival following interleukin-4 deprivation and is controlled by AP1 and AP1-like transcription factors

We have analyzed the interleukin-4 (IL-4)-triggered mechanisms implicated in cell survival and show here that IL-4 deprivation induces apoptotic cell death but does not modulate Bcl-2 or Bcl-x expression. Since Bcl-x expression is insufficient to ensure cell survival in the absence of IL-4, we speculate that additional molecules replace the antiapoptotic role of Bcl-2 and Bcl-x in an alternative IL-4-triggered pathway. Cell death is associated with Bcl-3 downregulation and Bcl-3 expression blocks IL-4 deprivation-induced apoptosis, suggesting that Bcl-3 acts as a survival factor in the absence of growth factor. To characterize the IL-4-induced regulation of murine Bcl-3 expression, we cloned the promoter of this gene. Sequencing of the promoter showed no TATA box element but did reveal binding sites for AP1, AP1-like, and SP1 transcription factors. Retardation gels showed that IL-4 specifically induces AP1 and AP1-like binding activity and that mutation of these binding sites abolishes the IL-4-induced Bcl-3 promoter activity, suggesting that these transcription factors are important in Bcl-3 promoter transactivation. IL-4 deprivation induces downregulation of Jun expression and upregulation of Fos expression, both of which are proteins involved in the formation of AP1 and AP1-like transcription factors. Overexpression of Jun family proteins transactivates the promoter and restores Bcl-3 expression in the absence of IL-4 stimulation. Taken together, these data describe a new biological role for Bcl-3 and define the regulatory pathway implicated in Bcl-3 expression.

IL-9 protects mice from Gram-negative bacterial shock: suppression of TNF-alpha, IL-12, and IFN-gamma, and induction of IL-10

IL-9 is a T cell-derived cytokine that, similar to the Th2 cytokines IL-4 and IL-10, has been implicated in the response to parasitic infections, allergy, and inflammatory processes. Because both IL-4 and IL-10 can confer protection to mice from septic shock, we investigated whether IL-9 may also be capable of conferring resistance on recipients of an otherwise lethal challenge with Pseudomonas aeruginosa. Prophylactic injections of rIL-9 appeared to be most effective in preventing the onset of a lethal shock, according to a pattern that was both dose dependent and time dependent. The protective effect of IL-9 was correlated with marked decreases in the production of the inflammatory mediators TNF-alpha, IL-12, and IFN-gamma, as well as the induction of the anti-inflammatory cytokine IL-10. Sustained levels of IL-9-specific transcripts could be detected in the spleens of mice recovering from sublethal P. aeruginosa infection. Therefore, IL-9 may be protective in septic shock via a rather unique mechanism involving a complex modulation of inflammatory and anti-inflammatory mediators.

Signals from the IL-9 receptor are critical for the early stages of human intrathymic T cell development

Highly purified human CD34+ hemopoietic precursor cells differentiate into mature T cells when seeded in vitro in isolated fetal thymic lobes of SCID mice followed by fetal thymus organ culture (FTOC). Here, this chimeric human-mouse FTOC was used to address the role of IL-9 and of the alpha-chain of the IL-9 receptor (IL-9Ralpha) in early human T cell development. We report that addition of the mAb AH9R7, which recognizes and blocks selectively the human high affinity alpha-chain of the IL-9R, results in a profound reduction of the number of human thymocytes. Analysis of lymphoid subpopulations indicates that a highly reduced number of cells undergo maturation from CD34+ precursor cells toward CD4+CD3-CD8-CD1+ progenitor cells and subsequently toward CD4+CD8+ double positive (DP) thymocytes. Addition of IL-9 to the FTOC resulted in an increase in cell number, without disturbing the frequencies of the different subsets. These data suggest that IL-9Ralpha signaling is critical in early T lymphoid development.

Cloning and characterization of IL-10-related T cell-derived inducible factor (IL-TIF), a novel cytokine structurally related to IL-10 and inducible by IL-9

IL-9 is a Th2 cytokine active on various cell types such as T and B lymphocytes, mast cells, and eosinophils, and potentially involved in allergy and asthma. To understand better the molecular mechanisms underlying the activity of this cytokine, we used a cDNA subtraction method to identify genes specifically induced by IL-9 in mouse T cells. One of the IL-9-regulated genes isolated by this approach turned out to encode a 180-amino acid long protein, including a potential signal peptide, and showing 22% amino acid identity with IL-10. This protein, designated IL-10-related T cell-derived inducible factor (IL-TIF), is induced by IL-9 in thymic lymphomas, T cells, and mast cells, and by lectins in freshly isolated splenocytes. Experiments concerning the mechanism regulating IL-TIF expression in T cells indicate that IL-9 induction is rapid (within 1 h), does not require protein synthesis, and depends on the activation of the Janus kinase (JAK)-STAT pathway. In vivo, constitutive expression of IL-TIF was detected by RT-PCR in thymus and brain, suggesting that the role of this new factor is not restricted to the immune system. Transfection of HEK293 cells with the IL-TIF cDNA resulted in the production of a glycosylated protein of about 25 kDa that was found to induce STAT activation in mesangial and neuronal cell lines. Further studies will have to address the possibility that some of the IL-9 activities may be mediated by IL-TIF.

Anti-IL-9 vaccination prevents worm expulsion and blood eosinophilia in Trichuris muris-infected mice

Production of neutralizing anti-IL-9 antibodies was induced in mice by immunization with mouse IL-9 coupled to ovalbumin. In the six mouse strains tested, a strong and long-lasting anti-IL-9 response developed with seric inhibitory titers of 10(-3) to 10(-5), as measured in an in vitro IL-9-dependent cell proliferation assay. In vivo, this immunization completely abrogated the increase in mast-cell protease-1 levels as well as the eosinophilia observed in mice after implantation of an IL-9-secreting tumor. We took advantage of this method to assess the role of IL-9 in infections with nematode Trichuris muris, where IL-9 production correlates with the resistant phenotype. C57BL/6 mice, which normally expel the parasite, became susceptible after anti-IL-9 immunization, demonstrating that IL-9 plays a critical role in this model. In addition, neutralization of IL-9 also inhibited parasite-induced blood eosinophilia. Taken together, the present data demonstrate the potency of our strategy to antagonize IL-9 in vivo and shows that this cytokine plays a major role in resistance against T. muris infection.

Proinflammatory cytokines and interleukin-9 exacerbate excitotoxic lesions of the newborn murine neopallium

Many prenatal and perinatal factors are hypothesized to play a role in the cause of cerebral palsy (CP). Epidemiological data implicate maternal-fetal infection and associated increase in circulating cytokines. Murine model data suggest that excitotoxic damage can produce pathological change in brain tissue consistent with lesions observed in CP. Specifically, on day 5 after birth, mouse pups injected with ibotenate, a glutamatergic analogue, develop transcortical necrosis and white matter cysts mimicking some human perinatal lesions associated with CP. The present study builds on this murine model to assess the modulating role of several cytokines on the development of excitotoxic lesions. Pups pretreated with interleukin (IL)-1beta, IL-6, IL-9, or tumor necrosis factor-alpha developed significantly larger ibotenate-induced cortical and white matter damage than controls; IL-4 did not produce such an effect. In a similar manner, IL-9-overexpressing transgenic pups developed ibotenate-induced brain lesions, which were significantly larger than those induced in nontransgenic control pups. Pretreatment with proinflammatory cytokines significantly increased neopallial microglial density without affecting astrocytic density; IL-9 or IL-4 did not produce a similar effect. To our knowledge, this is the first in vivo study to demonstrate that systemically administered proinflammatory cytokines and IL-9 exacerbate brain lesions that are similar to those found in human infants with CP.

Synergistic proliferation and activation of natural killer cells by interleukin 12 and interleukin 18

We investigated the effects of IL-12 and IL-18 on unstimulated murine splenocytes and observed that the two cytokines strongly synergized for their proliferation, whereas IL-12 and IL-18 alone were essentially inactive in this respect. Phenotypical and functional analyses of cells proliferating in response to IL-12 and IL-18 revealed that large granular Ly-49C(+)DX5(+)CD3(-)NK blasts were expanded in these cultures and that they displayed cytotoxic activity against Yac-1 cells, a murine NK cell target. Further analyses indicated three major differences between NK cells appearing in response to IL-12 and IL-18 and those derived in the presence of other NK cell growth factors, such as IL-2 or IL-15. First, a population of T-NK cells, i.e. expressing T cell (TCRalphabeta, CD3) and NK cell (Ly-49) markers, was detected amongst cells growing in IL-2 or IL-15 but not in cultures supplemented with IL-12 and IL-18. Second, most NK cells derived with IL-2 or IL-15 expressed the NK1.1 antigen, while those derived with IL-12 and IL-18 did not. Finally, striking differences were observed regarding cytokine production. Cells stimulated with IL-12 and IL-18 in combination, but not with IL-2 or IL-15, produced IFN-gamma, IL-3, IL-6 and TNF. IFN-gamma was not involved in the response of NK cells to IL-12 and IL-18, as indicated by experiments demonstrating that the combination of the two cytokines displayed similar effects on spleen cells from IFN-gammaR-knock-out mice. Receptor (IL-12Rbeta1, IL-12Rbeta2 and IL-18R) gene expression studies did not indicate that the mechanism underlying the synergy between IL-12 and IL-18 involved reciprocal induction of their receptors. Taken together, our results demonstrate that IL-12 and IL-18 exert striking synergistic activities for NK cell proliferation and activation, distinct from those induced by IL-2 or IL-15.

Distinct roles for STAT1, STAT3, and STAT5 in differentiation gene induction and apoptosis inhibition by interleukin-9

Interleukin-9 (IL-9) activates three distinct STAT proteins: STAT1, STAT3, and STAT5. This process depends on one tyrosine of the IL-9 receptor, which is necessary for proliferation, gene induction, and inhibition of apoptosis induced by glucocorticoids. By introduction of point mutations in amino acids surrounding this tyrosine, we obtained receptors that activated either STAT5 alone or both STAT1 and STAT3, thus providing us with the possibility to study the respective roles of these factors in the biological activities of IL-9. Both mutant receptors were able to prevent apoptosis, but only the mutant that activated STAT1 and STAT3 was able to support induction of granzyme A and L-selectin. In line with these results, constitutively activated STAT5 blocked glucocorticoid-induced apoptosis. In Ba/F3 cells, significant proliferation and pim-1 induction were observed with both STAT-restricted mutants, though proliferation was lower than with the wild-type receptor. These results suggest that survival and cell growth are redundantly controlled by multiple STAT factors, whereas differentiation gene induction is more specifically correlated with individual STAT activation by IL-9.

Interleukin-9-induced expression of M-Ras/R-Ras3 oncogene in T-helper clones

In an attempt to gain insight into the molecular mechanisms involved in interleukin-9 (IL-9) activities, representational difference analysis (RDA) was used to identify messages that are induced by IL-9 in a murine T-helper-cell clone. One of the isolated genes encodes for the newly described M-Ras or R-Ras3, which is part of the Ras gene superfamily. M-Ras expression was found to be induced by IL-9 but not IL-2 or IL-4 in various murine T-helper-cell clones, and this induction seems to be dependent on the JAK/STAT pathway. Contrasting with the potent upregulation of M-Ras expression, M-Ras was not activated by IL-9 at the level of guanosine triphosphate/guanosine diphosphate (GTP/GDP) binding. However, IL-3 increased GTP binding to M-Ras, suggesting that M-Ras induction might represent a new mechanism of cooperativity between cytokines such as IL-3 and IL-9. Constitutively activated M-Ras mutants induced activation of Elk transcription factor by triggering the MAP kinase pathway and allowed for IL-3-independent proliferation of BaF3 cells. Taken together, these results show that cytokines such as IL-9 can regulate the expression of a member of the RAS family possibly involved in growth-factor signal transduction.

IL-9 induces chemokine expression in lung epithelial cells and baseline airway eosinophilia in transgenic mice

Recent data have identified IL-9 as a key cytokine in determining susceptibility to asthma. These data are supported by the finding that allergen-exposed IL-9-transgenic mice exhibit many features that are characteristic of human asthma (airway eosinophilia, elevated serum IgE and bronchial hyperresponsiveness) as compared to the background strain. A striking feature of these animals is a robust peribronchial and perivascular eosinophilia after allergen challenge, suggesting that IL-9 is a potent factor in regulating this process. In an attempt to gain insights into the molecular mechanism governing IL-9 modulation of lung eosinophilia, we investigated the ability of this cytokine to induce the expression of CC-type chemokines in the lung because of their effect on stimulating eosinophil chemotaxis. Here we show that IL-9-transgenic mice in contrast to their congenic controls exhibit baseline lung eosinophilia that is associated with the up-regulation of CC-chemokine expression in the airway. This effect appears to be through a direct action of IL-9 because the addition of recombinant IL-9 to primary epithelial cultures and cell lines induced the expression of these chemokines in vitro. These data support a mechanism for IL-9 in regulating the expression of eosinophil chemotactic factors in lung epithelial cells.

Soluble tumor necrosis factor (TNF) receptors p55 and p75 and interleukin-10 downregulate TNF-alpha activity during the lung response to silica particles in NMRI mice

We have found reduced activity of tumor necrosis factor (TNF)-alpha accompanying resolving and fibrosing alveolitis induced in NMRI mice by mineral particles (MnO2 and SiO2, respectively), which is in apparent contradiction to the well-recognized proinflammatory and profibrotic activities of this cytokine. The objective of this study was to examine the mechanisms involved in this paradoxical response in NMRI mice. Although lung tissue messenger RNA (mRNA) levels for TNF-alpha were transiently (up to 15 d) and persistently (up to 120 d) upregulated in the resolving and fibrosing models, respectively, these changes were not accompanied by a parallel release of TNF-alpha protein, which was respectively transiently and persistently downregulated in bronchoalveolar lavage fluid and bronchoalveolar lavage cell cultures. The downregulation of the TNF-alpha protein was concurrent with the accumulation of recruited polymorphonuclear neutrophils (PMNs) in alveoli, and coculture experiments showed that PMN explanted from the lungs of mice treated with silica particles were able to downregulate the expression of TNF-alpha protein by naive alveolar macrophages. In addition, PMN depletion prevented the downregulation of TNF-alpha induced by silica, further establishing the role of PMNs in the downregulation of TNF-alpha. The possible degradation of TNF-alpha by proteolytic enzymes could be excluded. Marked increases in soluble p55 and p75 TNF receptors (sTNF-R), as well as in interleukin (IL)-10, paralleled the downregulation of TNF-alpha protein. The role of these mediators in the observed reduction of TNF-alpha activity was confirmed by immunoneutralizing the activity of p55 and p75 sTNF-R and by using IL-10-deficient animals. Because IL-10 also exerts profibrotic activity in addition to its antiinflammatory activity, the protracted overproduction of IL-10 observed in fibrosing alveolitis may help the understanding of why, in NMRI mice treated with silica particles, lung fibrosis develops in association with a downregulation of TNF-alpha.