The primary binding subunit of the human interleukin-4 receptor is also a component of the interleukin-13 receptor

Mphi1 and Mphi2 can be re-polarized by Th2 or Th1 cytokines, respectively, and respond to exogenous danger signals

Macrophages (Mphi) represent a dynamic cell population that develops and operates within a changing microenvironment. In parallel to Th1/Th2 cells, primary Mphi may undergo classical (Mphi1) or alternative (Mphi2) activation. Here, we investigated whether Mphi1/Mphi2 may be re-polarized by a secondary stimulation by Th1 or Th2 cytokines or by exogenous danger signals. We established that Mphi1IFNgamma respond to alternative activation by IL-4 and IL-10 by de novo secretion of Th2 cytokines AMAC-1 and IL-1ra, and by an increase in phagocytic capacity and a decrease in bactericidal activity. Vice versa, Mphi2 responded to classical activation by IFNgamma exhibiting reduced phagocytosis and significantly increased bacterial killing while being refractory regarding secretion of TNFalpha, IL-1beta and IL-12. In response to the bacterial danger signals LPS and MDP, both Mphi1 and Mphi2 produced IL-1beta and TNFalpha; in addition Mphi2 expressed the Th1-inducing cytokine IL-12. The ability of Mphi to be re-polarized and to react to exogenous danger signals is a precondition to down-regulate an outdated immune reaction and to retain the capacity to mount an adequate anti-bacterial response. Selective refractoriness of Mphi1 and Mphi2 to IFNgamma- and LPS-induced cytokine secretion may contribute to prevent autoimmunity.

Low expression of the interleukin (IL)-4 receptor alpha chain and reduced signalling via the IL-4 receptor complex in human neonatal B cells

Diminished neonatal antibody responses following infection or immunization may stem in part from intrinsic characteristics of neonatal B cells. In this study, we used B-cell subset sorting combined with gene expression assays to investigate major differences in the expression of host genes in neonatal and adult naïve B cells. We discovered significantly reduced expression of the interleukin (IL)-4 receptor alpha chain and reduced IL-4-induced signalling in neonatal B cells. Neonatal naïve B cells were susceptible to more rapid and more profound levels of apoptosis when cultured in vitro. They also exhibited a limited response to IL-4 treatment compared with adult cells. The expression level of the IL-13 receptor alpha 1 chain, a key component of the IL-13 receptor/IL-4 type II receptor, and the response to IL-13 treatment for protection against apoptosis in neonatal B cells were similar to those of the adult B cells. These studies suggest a possible mechanism underlying the limited magnitude and durability of neonatal antibody responses.

Effects of monomethylfumarate on dendritic cell differentiation

BACKGROUND

Fumaric acid esters (FAE) are effective against psoriasis vulgaris and monomethylfumarate (MMF) is believed to be the most bioactive metabolite of this medication. Earlier we found that the beneficial effects of FAE medication are accompanied by a downregulation of type 1 cytokine production by T-helper (Th) lymphocytes, which are important as they maintain a type 1 cytokine [interferon (IFN)-gamma, interleukin (IL)-2] environment in the skin lesions of psoriasis vulgaris patients and once maximal beneficial effects are obtained type 2 cytokine production is also decreased. In vitro MMF selectively induced type 2 cytokine production by primed Th lymphocytes, whereas type 1 cytokine production by and profileration of T lymphocytes were unaffected.

OBJECTIVES

As dendritic cells (DCs) present in these skin lesions play a key role in the activation of Th lymphocytes, we investigated the effects of MMF on monocyte-derived DC differentiation.

METHODS

Monocytes were differentiated into immature (i) DCs by cytokines with or without MMF. To establish whether these cells were differentiated into iDCs, we analysed the expression of cell surface molecules on these cells and the capacity to capture antigens using flow cytometry. Next, we determined whether these MMF-incubated (MMF-)iDCs could be matured by lipopolysaccharide (LPS) and whether MMF affected this responsiveness as well. For this purpose we measured cytokine production by these LPS-stimulated cells (MMF-DCs) using enzyme-linked immunosorbent assays as well as their ability to activate naive Th lymphocytes.

RESULTS

The presence of MMF during the differentiation of monocytes into iDCs resulted in cells that retained low levels of CD14 and hardly expressed CD1a. Upon maturation, these MMF-iDCs upregulated CD83 and costimulatory molecules and HLA-DR on their surface, indicating that these cells respond to LPS, albeit less than control iDCs. In addition, in response to LPS, MMF-iDCs did not decrease the capacity to capture antigens when compared with control iDCs. MMF-DCs hardly produced IL-12p70 and IL-10 and low levels of tumour necrosis factor (TNF)-alpha, whereas IL-8 produced by MMF-DCs and control DCs did not differ. Moreover, MMF-DCs were less able to induce IFN-gamma production by naive Th lymphocytes compared with control DCs. The production of IL-4 and IL-10 by naive Th lymphocytes cocultured with MMF-DCs did not differ from that by T cells cocultured with control DCs.

CONCLUSIONS

MMF inhibited the monocyte-derived DC differentiation resulting in cells that cannot be appropriately matured to DCs. Consequently, these MMF-DCs are less effective than control DCs in stimulating type 1 cytokine, but not type 2 cytokine production, in Th lymphocytes. This general immunomodulatory effect may in part explain the beneficial effects of FAE therapy in psoriasis.

Progesterone-induced blocking factor activates STAT6 via binding to a novel IL-4 receptor

Progesterone-induced blocking factor (PIBF) induces Th2-dominant cytokine production. Western blotting and EMSA revealed phosphorylation as well as nuclear translocation of STAT6 and inhibition of STAT4 phosphorylation in PIBF-treated cells. The silencing of STAT6 by small interfering RNA reduced the cytokine effects. Because the activation of the STAT6 pathway depends on the ligation of IL-4R, we tested the involvement of IL-4R in PIBF-induced STAT6 activation. Although PIBF does not bind to IL-4R, the blocking of the latter with an Ab abolished PIBF-induced STAT6 activation, whereas the blocking of the IL-13R had no effect. PIBF activated suppressor of cytokine signaling-3 and inhibited IL-12-induced suppressor of cytokine signaling-1 activation. The blocking of IL-4R counteracted all the described effects, suggesting that the PIBF receptor interacts with IL-4R alpha-chain, allowing PIBF to activate the STAT6 pathway. PIBF did not phosphorylate Jak3, suggesting that the gamma-chain is not needed for PIBF signaling. Confocal microscopic analysis revealed a colocalization and at 37 degrees C a cocapping of the FITC PIBF-activated PIBF receptor and PE anti-IL-4R-labeled IL-4R. After the digestion of the cells with phosphatidylinositol-specific phospholipase C, the STAT6-activating effect of PIBF was lost, whereas that of IL-4 remained unaltered. These data suggest the existence of a novel type of IL-4R composed of the IL-4R alpha-chain and the GPI-anchored PIBF receptor.

Inhibition of host signal transducer and activator of transcription factor 6 results in cure with cyclophosphamide and interleukin 12 immunotherapy

BACKGROUND

Interleukin (IL)-12 immunotherapy is highly effective against established immunogenic tumors. However, nonimmunogenic tumors fail to respond to IL-12 therapy. Analysis of tumor rejection of the immunogenic tumors shows that a preexisting antitumor immune response is required for an effective IL-12 response. It is not known whether this lack of a preexisting host antitumor immune response is a limiting factor for the lack of response to IL-12 therapy by nonimmunogenic tumors.

METHODS

Experiments were done using the spontaneously arising nonimmunogenic metastatic murine breast 4T1 carcinoma in normal and STAT6 knockout BALB/c mice.

RESULTS

4T1 is nonimmunogenic in normal mice, and established subcutaneous tumors are resistant to immunotherapy with cyclophosphamide (Cy) plus IL-12. However, in STAT6 knockout mice, 4T1 becomes immunogenic, and established 4T1 tumors are eradicated by Cy plus IL-12. Adoptive transfer of spleen cells from normal mice into STAT6 knockout mice before tumor inoculation reduces both the immunogenicity and response to Cy plus IL-12 immunotherapy of 4T1 in the recipient mice.

CONCLUSIONS

Cy plus IL-12 immunotherapy can eradicate nonimmunogenic tumors as long as a preexisting immunity is established in the tumor-bearing host. Furthermore, the STAT6 pathway is likely involved in the suppression of the development of host antitumor immunity.

Intracranial therapy of glioblastoma with the fusion protein DTIL13 in immunodeficient mice

A fusion protein consisting of human interleukin-13 and the first 389 amino acids of diphtheria toxin was assembled in order to target human glioblastoma cell lines in a murine intracranial model. In vitro studies to determine specificity indicated that the protein called DTIL13 was highly selective for human glioblastoma. In vivo, the maximum tolerated dose of DTIL13 was 1 microg/injection given every other day and repeated for 3 days. Doses that exceeded this amount resulted in weight loss and liver damage as determined by histology and enzyme assay. Experiments in IL-4 receptor knockout mice revealed that liver toxicity was receptor-related. This same dose given to nude mice with established U373 MG brain tumors resulted in significant reductions in tumor volume and significantly prolonged survival (p<0.0001). Magnetic resonance imaging (MRI) proved to be extremely useful in (i) determining the ability of DTIL13 to reduce tumor size and (ii) for studying toxicity since diffusion-weighted and gradient echo-weighted MRI revealed that vascular leak syndrome was not a limiting toxicity at this dose. These results suggest that DTIL13 is as effective in an intracranial rodent model as it was in a flank model in previous studies and that DTIL13 might be an effective treatment for glioblastoma multiforme.

Expression and targeting of interleukin-4 receptor for primary and advanced ovarian cancer therapy

Because the most characteristic property of ovarian cancer is i.p. spread, the majority of patients are diagnosed at an advanced stage, leading to limited availability of options for curative therapies. With an intent to identify targeted therapeutic approaches, we have observed that approximately 60% of 21 ovarian cancer tissue samples express a high density of interleukin-4 receptor (IL-4R), whereas normal ovarian tissues tested (n = 7) expressed no or low levels of IL-4R. To target IL-4R, we have developed IL-4 cytotoxin, in which circular-permuted IL-4 is fused to a mutated form of Pseudomonas exotoxin. This cytotoxin is specifically and highly cytotoxic to PA-1, IGROV-1, and SK-OV3 ovarian carcinoma cell lines in vitro. In addition, it shows remarkable antitumor activities against established s.c. ovarian tumors in immunodeficient animals. i.p. administration of IL-4 cytotoxin in mice with orthotopically implanted ovarian tumors caused regression of established tumors and prevented these animals from tumor metastasis. Continuous i.p. infusion of IL-4 cytotoxin prolonged survival of tumor-bearing mice even with bulky disease. These results indicate that IL-4R-targeted cytotoxin may be a useful agent for the management of patients with ovarian cancer, and further studies need to be done to evaluate its safety, tolerability, and efficacy.

Probabilistic regulation in TH2 cells accounts for monoallelic expression of IL-4 and IL-13

Il4 and Il13, closely linked genes, are expressed monoallelically in TH2 cells. Four different approaches (RNA FISH, cultures from Il13T-Il4/Il13-G4 mice, cultures from heterozygous Il13-Il4 double knockout mice, and a highly selected set of BABL/c*CAST/Ei clones displaying strong Il4 allelic bias) were utilized to study monoallelic expression of Il4 and coexpression of Il4 and Il13 on the same chromosome. There was a random probability for expression of one or two Il4 and one or two Il13 alleles; coexpression of cis and trans Il4 and Il13 alleles was equally probable. Histone H3 acetylation of CNS1, located in the Il13-Il4 intergenic region, was permissive for expression of IL-4 and IL-13 but did not determine the degree of their expression. Thus, monoallelism at the Il4 locus is a complex process; expression is linked to opening CNS1 but probability of expression is controlled at other sites. Based on these probabilities, individual cells randomly express Il4 and Il13 alleles.

Mechanisms underlying the maintenance of muscle hypercontractility in a model of postinfective gut dysfunction

BACKGROUND & AIMS

Acute gastroenteritis is a strong risk factor for the development of irritable bowel syndrome (IBS). We have developed an animal model in which transient acute infection leads to persistent muscle hypercontractility. Here, we investigate the mechanisms underlying the maintenance of this hypercontractility in the postinfective (PI) state.

METHODS

Muscle contraction and messenger RNA (mRNA) or protein expression of cytokines were examined from jejunal longitudinal muscle cells of NIH Swiss mice infected with Trichinella spiralis or incubated with or without cytokines.

RESULTS

During acute infection, interleukin (IL)-4 or IL-13, transforming growth factor (TGF)-beta1, and cyclooxygenase (COX)-2 were increased in the muscle layer ( P < .05). In the PI phase of the model, T helper (Th)2 cytokines returned to normal, but TGF-beta1 remained in the muscle ( P < .05). Exposure of muscle cells to IL-4 or IL-13 increased TGF-beta1 ( P < .01), COX-2 protein, and prostaglandin (PG)E 2 . Exposure of muscle cells to TGF-beta1 increased PGE 2 ( P < .05) and COX-2 protein. Incubation of tissue with IL-4, IL-13, TGF-beta1, or PGE 2 enhanced carbachol-induced muscle cell contractility ( P < .05). COX-2 inhibitor attenuated TGF-beta1-induced muscle hypercontractility ( P < .05).

CONCLUSIONS

These results support the hypothesis that Th2 cytokines induce muscle hypercontractility during infection by a direct action on smooth muscle. The maintenance of hypercontractility results from Th2 cytokine-induced expression of TGF-beta1 and the subsequent up-regulation of COX-2 and PGE 2 at the level of the smooth muscle cell. We propose that PI gut dysfunction reflects mediator production in the neuromuscular tissues and that this may occur in PI-IBS.

Interleukin-13 in asthma pathogenesis

Bronchial asthma is a complex disorder that is thought to arise as a result of aberrant T-lymphocyte responses to noninfectious environmental antigens. In particular, the symptoms of asthma are closely associated with the presence of activated T-helper 2 cell (Th2) cytokine-producing cells [interleukin (IL)-4, IL-5, IL-9, and IL-13] in the airway wall. Although each of the Th2 cytokines likely contributes to the overall immune response directed against environmental antigens, a substantial body of evidence points to a singular role for IL-13 in the regulation of the allergic diathesis. Initial studies in animal models of disease provided compelling evidence that IL-13, independently of other Th2 cytokines, was both necessary and sufficient to induce all features of allergic asthma. The importance of IL-13 in allergic disorders in humans is supported by consistent associations between tissue IL-13 levels and genetic variants in the IL-13 gene with asthma and related traits. With the preponderance of evidence continuing to support a pivotal role for IL-13 in allergic disorders, attention is now turned toward understanding the mechanisms by which this cytokine may mediate the pathophysiological features of allergic disease. The emerging paradigm is that IL-13 induces features of the allergic response via a complex array of actions on resident airway cells rather than through traditional effector pathways involving eosinophils and immunoglobulin E-mediated events. In light of these recent developments, this review explores our current understanding of the singular role of IL-13 in the pathogenesis of asthma, with a particular focus on new insights into the mechanisms by which IL-13 mediates various features of asthma.

Interleukin-4- and -13-induced hypercontractility of human intestinal muscle cells-implication for motility changes in Crohn's disease

Crohn's disease is an idiopathic inflammatory condition. However, little is known about the changes that occur in the muscularis externa, despite the fact that this tissue contributes to motility changes and stricture formation. We characterized immune activity in the muscularis externa from intestinal segments of Crohn's disease patients and evaluated the role of IL-4 and -13 as well as signal transducer and activator of transcription (STAT)6 in the contractility of the cultured human intestinal smooth muscle cells. CD3+ve cells (P < 0.01) and IL-4 protein (P < 0.01) were significantly increased in the muscularis externa of Crohn's disease patients compared with noninflamed controls. Preincubation of human cultured smooth muscle cells with IL-4 (P < 0.001) or IL-13 (P < 0.05) significantly enhanced carbachol-induced contraction, and this was significantly inhibited by the STAT6 inhibitor leflunomide (P < 0.0001). A similar profile was observed in muscle cells isolated from Crohn's disease patients. Both IL-4 and IL-13 increased specific STAT6-DNA binding in control cells, and this was inhibited by anti-STAT6 Ab (P < 0.05) or leflunomide (P < 0.05). IL-4 and IL-13 mediate the hypercontractility of intestinal muscle via a STAT6 pathway at the level of the smooth muscle cell. The STAT6 pathway may contribute to the hypercontractility of intestinal muscle in Crohn's disease.

The Trichuris muris system: a paradigm of resistance and susceptibility to intestinal nematode infection

Gastrointestinal helminths infect over 1 billion people worldwide. Although rarely causing death, such diseases are associated with high levels of morbidity and furthermore bear a large economic burden within areas where infections are endemic. Trichuris muris, a natural intestinal parasite of mice has been extensively utilised as a laboratory model for the study of human whipworm Trichuris trichiura. This has proven to be an invaluable tool in dissecting the different components involved in immunity to trichuris infection. Moreover, it has become a paradigm of cytokine mediated immunity to gastrointestinal nematodes in general. It is well established that resistance and susceptibility to T. muris infection are tightly associated with the generation of a T helper 2 (TH2) or a T helper 1 (TH1) immune response, respectively. This review gives a detailed account of the experimental work which has provided us with this knowledge, and further builds upon this, by focusing upon the most recent developments and important findings from this host-parasite relationship.

Mechanism of action of interleukin-13 antagonist (IL-13E13K) in cells expressing various types of IL-4R

As interleukin (IL)-13 and IL-4 play a major role in various diseases including asthma, allergy, and malignancies, it is desirable to generate a molecule that blocks the effects of both cytokines. We previously generated a human IL-13 mutant (IL-13E13K), which is a powerful antagonist of IL-13, blocking the biological activities of IL-13. We now show that IL-13E13K also competitively inhibits signaling and biological activities of IL-4 through type II and partially through type III IL-4 receptor (R) system. IL-13E13K completely blocked the IL-4-induced phosphorylation of STAT6 and IL-4-dependent protein synthesis in cells expressing type II and partially type III IL-4R but not type I IL- 4R. Consistent with the inhibition of biological activities, IL-13E13K inhibited IL-4 binding to type II IL-4R-expressing cells but not to type I IL-4R-expressing cells. The inhibition efficiency of IL-4 binding by IL-13E13K was relatively lower compared to wtIL-13 even though IL-13E13K bound to IL-13Ralpha1 positive cells with a similar affinity to wtIL-13. These results indicate that Glu13 in IL-13 associates with IL-4Ralpha, and mutation to lysine decreases its binding ability to IL-4Ralpha chain. IL-13E13K binds to IL- 13Ralpha1, which is shared by both IL-13R and IL-4R systems. Consequently, IL-13E13K inhibits IL-4 binding to these cells and prevents heterodimer formation between IL-13Ralpha1 and IL-4Ralpha chains. This interference by IL-13E13K blocks the biological activities of not only IL-13 but also partially of IL-4. Thus, IL-13E13K may be a useful agent for the treatment of diseases such as asthma, allergic rhinitis, and cancer, which are dependent on signaling through both IL-4 and IL-13 receptors.

IL-4 and IL-13 up-regulate intestinal trefoil factor expression: requirement for STAT6 and de novo protein synthesis

The development of intestinal goblet cell hyperplasia/hypertrophy during nematode infection involves the Th2 cytokines IL-4 and IL-13 via STAT6 activation. This is thought to play an important role in host protective immunity against the infection. In this study we demonstrate that IL-4 and IL-13 up-regulate the specific goblet cell product trefoil factor-3 (TFF3) from the mucus-producing HT-29 CL.16E and HT-29 cells selected by adaptation to methotrexate. Up-regulation of TFF3 mRNA and protein levels occurred in a time- and dose-dependent fashion and was accompanied by up-regulation of the goblet cell product mucin 2 (MUC2). Addition of actinomycin D before IL-4/IL-13 stimulation led to decreases in TFF3 mRNA levels similar to those observed in controls without IL-4/IL-13. Furthermore, IL-4-mediated increased TFF3 transcription required de novo protein synthesis. Stable transfection of HT-29 CL.16E cells with a truncated dominant-negative form of STAT6 produced a cell line that was unresponsive to IL-4/IL-13. Although only one consensus STAT6 binding site is contained in the TFF3 gene, located in the intron 1, it did not operate as an enhancer in the context of an SV40 promoter/luciferase construct. Thus, STAT6 activation mediates a transcriptional enhancement of TFF3 by induction of de novo synthesized protein in goblet cells.

Up-regulation of interleukin-13 receptor alpha1 on human keratinocytes in the skin of psoriasis and atopic dermatitis

BACKGROUND

Interleukin (IL)-13 is a pleiotropic cytokine, which shares many biological functions with IL-4. The receptor subunits of IL-13 consist of IL-4Ralpha, IL-13Ralpha1 and IL-13Ralpha2. The regulatory mechanisms of the IL-13Ralpha expression in the keratinocytes of certain skin disease have not been known.

OBJECTIVE

To clear the roles of IL-13 and the regulatory mechanisms of its receptor in atopic dermatitis (AD) and psoriasis.

METHOD

The expression of IL-13Ralpha1 in the skin of AD and psoriasis was investigated by immunohistochemistry. The regulation of IL-13Ralpha mRNA in the skin and human primary keratinocyte (HPK) was investigated by quantitative PCR. The secretion of IL-6 and RANTES from HPK was measured by ELISA.

RESULTS

The expression of IL-13Ralpha1 was more prominent on the suprabasal keratinocytes in the skin of AD and striking increase of staining was observed on all layers of keratinocyte in the skin of psoriasis. The mRNA of IL-13Ralpha1, but not of IL-13Ralpha2 was overexpressed in both skin of AD and psoriasis. In vitro experiment using HPK demonstrated that IFN-gamma, IL-13 but not IL-4 could up-regulate the mRNA expression of IL-13Ralpha1. In contrast, IL-13Ralpha2 mRNA expression was up-regulated by IFN-gamma plus IL-4. Furthermore, the stimulation of HPK with IFN-gamma plus IL-13 and/or IL-4 resulted in significant enhancement of IL-6 and RANTES secretion.

CONCLUSION

These findings indicate that IL-4 and IL-13 have different regulatory effects on the expression of IL-13Ralpha1 and alpha2, and the overexpression of IL-13Ralpha1 may play some roles in the pathogenesis of chronic stage of AD or psoriasis.

Induction of macrophage insulin-like growth factor-I expression by the Th2 cytokines IL-4 and IL-13

Macrophage-derived insulin-like growth factor-I (IGF-I) has long been implicated in the pathogenesis of the interstitial lung disease, idiopathic pulmonary fibrosis, in part, by its ability to 1) stimulate the proliferation and survival of fibroblasts and myofibroblasts and 2) promote collagen matrix synthesis by these cells. However, little is known about the mechanisms that stimulate the expression of IGF-I by macrophages. Previous studies have shown that the development of pulmonary fibrosis is accompanied by enhanced expression of Th2-profile cytokines, especially IL-4, and diminished expression of Th1 cytokines, including IFN-gamma. In addition, in vitro studies have shown that IFN-gamma down-regulates the expression of IGF-I. Thus, the paucity of IFN-gamma in the fibrotic lung may favor increased growth factor production by allowing Th2 cytokines to predominate. In view of these findings, we investigated the hypothesis that Th2 cytokines stimulate the expression of IGF-I by macrophages. Incubation with IL-4 or IL-13 led to concentration- and time-dependent increases in the expression of IGF-I mRNA and the secretion of IGF-I protein by mouse macrophages as a consequence of increased transcription of IGF-I pre-mRNA. Exposure of macrophages to IL-4 in the presence of IFN-gamma inhibited the increase in the expression of IGF-I. Studies using STAT6-deficient macrophages indicated that the increase in IGF-I expression was dependent on STAT6. In addition, the down-regulation of IGF-I expression by IFN-gamma was absent in STAT1-deficient macrophages. Collectively, these findings define a homeostatic mechanism in which Th2 cytokines promote, and Th1 cytokines inhibit, the expression of IGF-I by macrophages.

Epicutaneous exposure to protein antigen and food allergy

BACKGROUND

The aetiology of food allergy remains unclear. Although failure to develop or breakdown in oral tolerance has been proposed, the existence of physiologic sensitization routes other than the gastrointestinal tract cannot be excluded.

OBJECTIVE

The purpose of this study is to clarify whether or not exposure to allergen through the skin can promote food allergy.

METHODS

BALB/c mice were shaved on the back, and a patch impregnated with 100 micro g of ovalbumin (OVA) was applied to the dorsal skin for a 1-week period and then removed. After three courses of sensitization, OVA-specific antibodies in sera were measured, and then mice were orally challenged with 50 mg of OVA. Anaphylactic symptoms, plasma histamine levels, and histology of intestines and lungs after oral challenge were examined.

RESULTS

Epicutaneous (EC) sensitization of mice to OVA induced a high level of OVA-specific IgE. Subsequent oral challenge with OVA resulted in symptoms of systemic anaphylaxis with elevated levels of plasma histamine as well as histological changes in both intestines and lungs. In the presence of anti-IL-4 antibodies, EC sensitization failed to provoke an IgE response, but still induced a Th2-predominant cellular immune response in lungs after oral challenge.

CONCLUSION

We demonstrated for the first time that food allergy can be induced by allergen exposure through the skin. Our results identify a novel role of EC sensitization in the pathogenesis of food allergy.

Overexpression of interleukin-4 in lungs of mice impairs elimination of Histoplasma capsulatum

Protection against the pathogenic fungus Histoplasma capsulatum requires Th1 cytokines. Since interleukin-4 (IL-4) can inhibit both Th1 cytokine production and activity, we examined the effects of overproduction of IL-4 in the lung on the course of pulmonary histoplasmosis. IL-4 lung transgenic mice manifested a higher fungal burden in their lungs, but not spleens, compared to wild-type infected controls. Despite the higher burden, the transgenic animals were ultimately capable of controlling infection. The adverse effects of IL-4 on H. capsulatum elimination were not observed during the early phase of infection (days 1 to 3) but were maximal at day 7 postinfection, prior to the induction of cell-mediated immunity. Analysis of total body and lung cytokine levels revealed that gamma interferon and tumor necrosis factor alpha production were not inhibited in the presence of excess IL-4. Our results with transgenic mice were supported by additional in vivo studies in which allergen induction of pulmonary IL-4 was associated with delayed clearance of H. capsulatum yeast and increased fungal burden. These findings demonstrate that excess production of endogenous IL-4 modulates protective immunity to H. capsulatum by delaying clearance of the organism but does not prevent the generation of a Th1 response that ultimately controls infection.

IL-13 receptors and signaling pathways: an evolving web

IL-13 is an immunoregulatory cytokine secreted predominantly by activated T(H)2 cells. Over the past several years, it has become evident that IL-13 is a key mediator in the pathogenesis of allergic inflammation. IL-13 shares many functional properties with IL-4, stemming from the fact that they share a common receptor subunit, the alpha subunit of the IL-4 receptor (IL-4Ralpha). Characterization of IL-13-deficient mice, IL-4-deficient mice, and IL-4 receptor alpha-deficient (IL-4Ralpha(-/-)) mice have demonstrated nonredundant roles for IL-13. IL-13 mediates its effects by interacting with a complex receptor system comprised of IL-4Ralpha and two IL-13 binding proteins, IL-13Ralpha1 and IL-13Ralpha2. IL-13 receptors are expressed on human B cells, basophils, eosinophils, mast cells, endothelial cells, fibroblasts, monocytes, macrophages, respiratory epithelial cells, and smooth muscle cells. However, functional IL-13 receptors have not been demonstrated on human or mouse T cells. Thus unlike IL-4, IL-13 does not appear to be important in the initial differentiation of CD4 T cells into T(H)2-type cells but rather appears to be important in the effector phase of allergic inflammation. This is further supported by many in vivo observations, including that administration of IL-13 resulted in allergic inflammation, tissue-specific overexpression of IL-13 in the lungs of transgenic mice resulted in airway inflammation and mucus hypersecretion, IL-13 blockade abolished allergic inflammation independently of IL-4, and IL-13 appears to be more important than IL-4 in mucus hypersecretion. Given the importance of IL-13 as an effector molecule, regulation at the level of its receptors might be an important mechanism of modulating IL-13 responses and thus propagation of the allergic response. Accordingly, IL-13 is an attractive, novel therapeutic target for pharmacologic intervention in allergic disorders. This review will summarize the current understanding of the IL-13 receptors and signaling pathways, emphasizing recent observations.

IL-13 is necessary, not simply sufficient, for epicutaneously induced Th2 responses to soluble protein antigen

Th2 responses are clearly involved in the pathogenesis of atopic disease. Thus, understanding the factors responsible for Th2 sensitization at sites of allergen exposure, such as airway and skin, is crucial for directing therapeutic or preventive strategies. Contrary to other models of Th2 sensitization to proteins, we have reported that Th2 responses induced by epicutaneous exposure to OVA are IL-4 independent. Combined deficiency of both IL-4 and IL-13 signaling did prevent Th2 generation, suggesting that IL-13 was mediating these IL-4-independent responses. It was not clear, however, whether IL-13 was simply replacing the need for IL-4 in genetically deficient mice or if IL-13 played a unique role. In the present study, we show that Th2 responses induced by epicutaneous OVA exposure (including lung inflammatory responses after inhaled Ag challenge, OVA-specific IgG1, and draining lymph node IL-5 production) are impaired in IL-13-deficient (IL-13(-/-)) mice compared with wild type. In contrast, i.p. sensitization of IL-13(-/-) mice resulted in responses equivalent to wild type. Generation of contact hypersensitivity to dinitrofluorobenzene, which involves Th1 and CD8(+) effector cells, was also intact in IL-13(-/-) mice. Taken together, the data indicate that IL-13 is the major inducer of Th2 generation in the cutaneous microenvironment, being required independently of IL-4. This fact, in combination with the known abundance of IL-13 in atopic dermatitis skin lesions, emphasizes the potentially important role of the skin as a site for Th2 sensitization to environmental allergens, particularly in atopic individuals.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

Biochemical and functional characterization of human transmembrane tryptase (TMT)/tryptase gamma. TMT is an exocytosed mast cell protease that induces airway hyperresponsiveness in vivo via an interleukin-13/interleukin-4 receptor alpha/signal transducer and activator of transcription (STAT) 6-dependent pathway

Transmembrane tryptase (TMT)/tryptase gamma is a membrane-bound serine protease stored in the secretory granules of human and mouse lung mast cells (MCs). We now show that TMT reaches the external face of the plasma membrane when MCs are induced to degranulate. Analysis of purified recombinant TMT revealed that it is a two-chain neutral protease. Thus, TMT is the only MC protease identified so far which retains its 18-residue propeptide when proteolytically activated. The genes that encode TMT and tryptase betaI reside on human chromosome 16p13.3. However, substrate specificity studies revealed that TMT and tryptase betaI are functionally distinct even though they are approximately 50% identical. Although TMT is rapidly inactivated by the human plasma serpin alpha(1)-antitrypsin in vitro, administration of recombinant TMT (but not recombinant tryptase betaI) into the trachea of mice leads to airway hyperresponsiveness (AHR) and increased expression of interleukin (IL) 13. T cells also increase their expression of IL-13 mRNA when exposed to TMT in vitro. TMT is therefore a novel exocytosed surface mediator that can stimulate those cell types that are in close proximity. TMT induces AHR in normal mice but not in transgenic mice that lack signal transducer and activator of transcription (STAT) 6 or the alpha-chain of the cytokine receptor that recognizes both IL-4 and IL-13. Based on these data, we conclude that TMT is an exocytosed MC neutral protease that induces AHR in lungs primarily by activating an IL-13/IL-4Ralpha/STAT6-dependent pathway.

Targeting glioblastoma multiforme with an IL-13/diphtheria toxin fusion protein in vitro and in vivo in nude mice

Fusion proteins composed of tumor binding agents and potent catalytic toxins show promise for intracranial therapy of brain cancer and an advantage over systemic therapy. Glioblastoma multiforme (GBM) is the most common form of brain cancer and overexpresses IL-13R. Thus, we developed an interleukin-13 receptor targeting fusion protein, DT(390)IL13, composed of human interleukin-13 and the first 389 amino acids of diphtheria toxin. To measure its ability to inhibit GBM, DT(390)IL13 was tested in vitro and found to inhibit selectively the U373 MG GBM cell line with an IC(50) around 12 pmol/l. Cytotoxicity was neutralized by anti-human-interleukin-13 antibody, but not by control antibodies. In vivo, small U373 MG glioblastoma xenografts in nude mice completely regressed in most animals after five intratumoral injections of 1 microg of DT(390)IL13 q.o.d., but not by the control fusion protein DT(390)IL-2. DT(390)IL13 was also tested against primary explant GBM cells of a patient's excised tumor and the IC(50) was similar to that measured for U373 MG. Further studies showed a therapeutic window for DT(390)IL13 of 1-30 microg/injection and histology studies and enzyme measurements showed that the maximum tolerated dose of DT(390)IL13 had little effect on kidney, liver, spleen, lung and heart in non-tumor-bearing immunocompetent mice. Together, these data suggest that DT(390)IL13 may provide an important, alternative therapy for brain cancer.

Role of IL-4, IL-13, and STAT6 in inflammation-induced hypercontractility of murine smooth muscle cells

T helper 2 (Th2) cytokines interleukin (IL)-4 and IL-13, which activate signal transducer and activator of transcription 6 (STAT6) are expressed in the muscularis externa during nematode infection and are candidate mediators of the associated hypercontractility. To determine the locus of action of these cytokines, we examined the IL-4- and IL-13-induced hypercontractility of the isolated muscle cells from STAT6 +/+ and STAT6 -/- mice. We compared the results with cells isolated from Trichinella spiralis-infected STAT6 +/+ and STAT6 -/- mice. Carbamylcholine chloride (Carbachol) induced the contraction of jejunal muscle cells in a concentration-dependent manner maximal contraction (R(max) 26.7 +/- 1.9%). Cells from T. spiralis-infected STAT6 -/- mice showed the hypertrophy (cell lengths 41.4 +/- 0.8 to 89.0 +/- 8.7 microm) and hypercontractility (R(max) 37.5 +/- 1.3%) induced by infection. IL-4Ralpha mRNA was detected in dispersed smooth muscle cells. Incubation of longitudinal muscle-myenteric plexus (LMMP) with IL-4 and IL-13 enhanced Carbachol-induced muscle contraction (R(max) 35.5 +/- 1.9 and 32.4 +/- 2.9%, respectively). Incubation of LMMP from STAT6 -/- mice with IL-4 did not enhance the contraction. The hypercontractility in T. spiralis-infected mice was attenuated in STAT6 -/- mice (P < 0.02). These results indicate both IL-4 and IL-13 induce hypercontractility of muscle cells via the STAT6 pathway, and this is the basis for hypercontractility observed in T. spiralis-infected mice.

IL-13 alters mucociliary differentiation and ciliary beating of human respiratory epithelial cells

In animal models of asthma, interleukin-13 (IL-13) induces goblet cell metaplasia, eosinophil infiltration of the bronchial mucosa, and bronchial hyperreactivity, but the basis of its effects on airway epithelia remain unknown. Lesions of the epithelial barrier, frequently observed in asthma and other chronic lung inflammatory diseases, are repaired through proliferation, migration, and differentiation of epithelial cells. An inflammatory process may then, therefore, influence epithelial regeneration. We have thus investigated the effect of IL-13 on mucociliary differentiation of human nasal epithelial cells in primary culture. We show that IL-13 alters ciliated cell differentiation and increases the proportion of secretory cells. IL-13 downregulates the actin-binding protein ezrin and other cytoskeletal components. IL-13 also impairs lateral cell contacts and interferes with the apical localization of ezrin seen in differentiated ciliated cells. In addition, an IL-4 antagonistic mutant protein (Y124D), which binds to the IL-4 receptor alpha subunit, a common chain of IL-4 and IL-13 receptors, inhibits IL-13's effects. IL-13 also decreases ciliary beat frequency in a time- and dose-dependent manner. These results suggest that, in human allergic asthmatic responses, IL-13 affects both ciliated and secretory cell differentiation, leading to airway damage and obstruction.

Lung epithelial barrier function and wound healing are decreased by IL-4 and IL-13 and enhanced by IFN-gamma

To understand the effects of cytokines on epithelial cells in asthma, we have investigated the effects of interleukin (IL)-4, IL-13, and interferon (IFN)-gamma on barrier function and wound healing in Calu-3 human lung epithelial cells. IL-4 and IL-13 treatment of Calu-3 cells grown on Transwell filters resulted in a 70-75% decrease in barrier function as assessed by electrophysiological and [(14)C]mannitol flux measurements. In contrast, IFN-gamma enhanced barrier function threefold using these same parameters. Cells treated concurrently with IFN-gamma and IL-4 or IL-13 showed an initial decline in barrier function that was reversed within 2 days, resulting in barrier levels comparable to control cells. Analysis of the tight junction-associated proteins ZO-1 and occludin showed that IL-4 and IL-13 significantly reduced ZO-1 expression and modestly decreased occludin expression compared with controls. IFN-gamma, quite unexpectedly given its enhancing effect on barrier function, reduced expression of ZO-1 and occludin to almost undetectable levels compared with controls. In wound-healing assays of cells grown on collagen I, IL-4 and IL-13 decreased migration, whereas IFN-gamma treatment enhanced migration, compared with control cells. Addition of IFN-gamma, in combination with IL-4 or IL-13, restored migration of cells to control levels. Migration differences observed between the various cytokine treatments was correlated with expression of the collagen I-binding alpha(2)beta(1)-integrin at the leading edge of cells at the wound front; alpha(2)beta(1)-integrin expression was decreased in IFN-gamma-treated cells compared with controls, whereas it was highest in IL-4- and IL-13-treated cells. These results demonstrate that IL-4 and IL-13 diminish the capacity of Calu-3 cells to maintain barrier function and repair wounds, whereas IFN-gamma promotes epithelial restitution by enhancing barrier function and wound healing.

IL-25 induces IL-4, IL-5, and IL-13 and Th2-associated pathologies in vivo

We have characterized a cytokine produced by Th2 cells, designated as IL-25. Infusion of mice with IL-25 induced IL-4, IL-5, and IL-13 gene expression. The induction of these cytokines resulted in Th2-like responses marked by increased serum IgE, IgG(1), and IgA levels, blood eosinophilia, and pathological changes in the lungs and digestive tract that included eosinophilic infiltrates, increased mucus production, and epithelial cell hyperplasia/hypertrophy. In addition, our studies show that IL-25 induces Th2-type cytokine production by accessory cells that are MHC class II(high), CD11c(dull), and lineage(-). These results suggest that IL-25, derived from Th2 T cells, is capable of amplifying allergic type inflammatory responses by its actions on other cell types.

Interleukin-13 mediates airways hyperreactivity through the IL-4 receptor-alpha chain and STAT-6 independently of IL-5 and eotaxin

Interleukin (IL)-13 is a central mediator of the processes underlying the induction of airways hyperreactivity (AHR) in the allergic lung. However, the mechanisms by which IL-13 induces AHR and the associated role of inflammatory infiltrates as effector cells has not been fully elucidated. In this investigation, we show that intratracheal administration of IL-13 induces AHR in the presence and absence of inflammation. The initial AHR response (peak, 6 to 24 h; preinflammatory phase [PIP]) was dissociated from inflammation (eosinophilia) and mucus hypersecretion but was critically regulated by signaling through the IL-4 receptor alpha chain (IL-4Ralpha) and signal transducers and activators of transcription (STAT)-6. The second response (> 24 h, inflammatory phase [IP]) was characterized by an amplified AHR, eosinophil accumulation, and mucus hypersecretion. These features of the IP were not observed in IL-4Ralpha- or STAT-6-deficient mice. To determine the role of eosinophils in the induction of IP AHR and mucus hypersecretion, we administered IL-13 to IL-5-, eotaxin-, and IL-5/eotaxin- deficient mice. IL-13-mediated eosinophil accumulation was significantly attenuated (but not ablated) in IL-5-, eotaxin-, or IL-5/eotaxin-deficient mice. However, IL-13-induced AHR and mucus secretion occurred independently of IL-5 and/or eotaxin. These findings demonstrate that IL-13 can induce AHR independently of these eosinophil regulatory cytokines and mucus hypersecretion. Furthermore, IL-13-induced AHR, eosinophilia, and mucus production are critically dependent on the IL-4Ralpha chain and STAT-6.

IL-13 and IL-4 up-regulate cysteinyl leukotriene 1 receptor expression in human monocytes and macrophages

The cysteinyl (Cys) leukotrienes (LT)C(4), LTD(4), and LTE(4), are lipid mediators that have been implicated in the pathogenesis of asthma. The human LTD(4) receptor (CysLT(1)R) was recently cloned and characterized. The present work was undertaken to study the potential modulation of CysLT(1)R expression by the Th2 cytokines IL-13 and IL-4. In this study, we report that IL-13 up-regulates CysLT(1)R mRNA levels, with consequently enhanced CysLT(1)R protein expression and function in human monocytes and monocyte-derived macrophages. CysLT(1)R mRNA expression was augmented 2- to 5-fold following treatment with IL-13 and was due to enhanced transcriptional activity. The effect was observed after 4 h, was maximal by 8 h, and maintained at 24 h. IL-4, but not IFN-gamma, induced a similar pattern of CysLT(1)R up-regulation. Monocytes pretreated with IL-13 or IL-4 for 24 h showed enhanced CysLT(1)R protein expression, as assessed by flow cytometry using a polyclonal anti-CysLT(1)R Ab. They also showed enhanced responsiveness to LTD(4), but not to LTB(4), in terms of Ca(2+) mobilization, as well as augmented chemotactic activity. Our findings suggest a possible mechanism by which IL-13 and IL-4 can modulate CysLT(1)R expression on monocytes and macrophages, and consequently their responsiveness to LTD(4), and thus contribute to the pathogenesis of asthma and allergic diseases.

Expression of interleukin 13 receptor in glioma and renal cell carcinoma: IL13Ralpha2 as a decoy receptor for IL13

Glioma and renal cell carcinoma (RCC) cells express high affinity interleukin 13 (IL13) binding sites, but only RCC cell proliferation was inhibited by IL13. Both of these two cell types are IL2-receptor (gamma)c chain-negative. We thus used these cell models to investigate the patterns of expression of IL13Ralpha1, IL13Ralpha2, and IL4Ralpha chains and the role of IL13Ralpha2 in the response to IL13. Using new specific antibodies and flow cytometry, we observed a similar surface expression of IL4Ralpha and IL13Ralpha1 chains in most RCC and glioma cells, whereas IL13Ralpha2 was only present on five of six glioma cell lines. In all glioma cell lines, the amount of IL13Ralpha2 expression was 10 to 30 times higher than that of the two other chains. Although there was no surface or intracellular expression of IL13Ralpha2, its mRNA was detected in three of seven RCC cell lines. The expression on RCC cells of IL13Ralpha2 mRNA and/or that of high-affinity IL13 binding sites is not sufficient to predict IL13Ralpha2 protein expression. Blocking experiments showed that IL4 and IL13 strongly inhibited RCC cell proliferation through a unique receptor composed of IL4Ralpha and IL13Ralpha1 chains. Using RCC cells stably transfected with IL13Ralpha2 cDNA, we showed that the overexpression of IL13Ralpha2 decreased the response to IL13 but not that to IL4. Our results demonstrate that IL13Ralpha2 acts as a decoy receptor for IL13 and that it may exert a tight regulation of IL13 activity without impairing the IL4 response of the same cell target.

Differential effect of IL-4 and IL-13 on CD44 expression in the Burkitt's lymphoma B cell line BL30/B95-8 and in Epstein-Barr virus (EBV) transformed human B cells: loss of IL-13 receptors on Burkitt's lymphoma B cells

IL-4 and IL-13, cytokines with similar biological effects may influence growth and progression of B-cell tumors through regulation of key cell surface molecules important in intercellular communications. In this study, we demonstrate that IL-4 and IL-13 exhibited differential effects on CD23 and CD44 expression and binding to hyaluronan in BL30/B95-8, a Burkitt's lymphoma (BL), and MK3.31, an Epstein-Barr virus transformed normal human B cell line (B-LCL). Studies conducted to understand the molecular mechanisms underlying this differential effect show that IL-4 induced phosphorylation of JAK1, JAK3, and STAT6 in BL30/B95-8 cells and of JAK3 and STAT6 in MK 3.31 cells. In contrast, IL-13 failed to induce the phosphorylation of JAK kinases or STAT6 proteins in these cell lines. The inability of BL30/B95-8 cells to respond to IL-13 was attributed to the loss of expression of IL-13R subunits alpha1 and alpha2, a finding confirmed for a number of other BL cell lines examined.

Molecular cloning of canine IL-13 receptor alpha chain (alpha1 and alpha2) cDNAs and detection of corresponding mRNAs in canine tissues

This communication reports the cloning of cDNAs encoding two canine IL-13 receptor alpha chains (caIL-13Ralpha1 and caIL-13Ralpha2). As described for the members of type-I cytokine receptors, both caIL-13Ralpha1 and caIL-13Ralpha2 were found to contain the highly conserved motifs, such as cysteine and tryptophan residues in their N-terminal portion and the WSXWS at C-terminus. The isolated caIL-13Ralpha1 cDNA contains 1547 nucleotides with an open reading frame that encodes 405 amino acid residues. Canine IL-13Ralpha1 is 82.0 and 69.3% identical to human and mouse IL-13Ralpha1s, respectively, at the amino acid level. Canine IL-13Ralpha1 has an almost identical cytoplasmic domain to its human and mouse counterparts. The isolated caIL-13Ralpha2 cDNA contains 1454 nucleotides and encodes an open reading frame of 386 amino acid residues. Canine IL-13Ralpha2 is 62.6 and 47.5% identical to its human and mouse counterparts, respectively, at the amino acid level. Using RT-PCR with caIL-13Ralpha1 and caIL-13Ralpha2 specific primers, mRNAs of caIL-13Ralpha1 and caIL-13Ralpha2 were detected in most dog tissues. In addition, RT-PCR detected caIL-13Ralpha1 mRNA in one of two canine mastocytoma (C2 but not Br) cell lines and in a canine macrophage-derived cell line (DH82). CaIL-13Ralpha2 mRNA was detected in all three canine cell lines.

Disrupting Il13 impairs production of IL-4 specified by the linked allele

Interleukin 13-deficient (IL-13-/-) mice express a defect in priming for IL-4 production that is not corrected by adding IL-13 to the priming culture. This is partly accounted for by the consumption of IL-4 without endogenous replacement during culture of IL-13-/- CD4+ T cells. We examined cells from mice in which disrupted Il13 was linked to wild-type Il4 on one chromosome and wild-type Il13 was linked to a "knocked-in" green fluorescent protein (Gfp) gene in the Il4 locus. Our results show that the deficit in IL-4 production was due, at least in part, to a cis effect, in which disrupted Il13 diminished IL-4 production from the linked Il4 gene.

Interleukin (IL)-13 and IL-4 inhibit proliferation and stimulate IL-6 formation in human osteoblasts: evidence for involvement of receptor subunits IL-13R, IL-13Ralpha, and IL-4Ralpha

Interleukin-13 (IL-13) inhibits cell proliferation and stimulates interleukin-6 (IL-6) formation in isolated human osteoblasts (hOBs). Because the related cytokine, interleukin-4 (IL-4), is known to exert effects similar to IL-13 in other tissues, and because IL-4 has been implicated as a regulator of bone metabolism, we compared the effects of IL-13 and IL-4 on cell proliferation, IL-6 synthesis, the expression of osteoblastic phenotypic markers in hOB cultures. Also, the receptor proteins mediating these effects in hOBs have been partly characterized. IL-4 and IL-13 dose-dependently inhibited [(3)H]-thymidine incorporation into the DNA of human osteoblasts and stimulated secretion of IL-6 into culture supernatants. IL-13 and IL-4 also increased the mRNA levels of IL-6, as measured by RNAse protection assay. Furthermore, IL-13 and IL-4 dose-dependently enhanced alkaline phosphatase (ALP) activity, but did not affect osteocalcin or collagen type I synthesis. IL-4 was tenfold more potent than IL-13 in inducing both ALP activity and IL-6 secretion, whereas the cytokines were equipotent as inhibitors of cell proliferation. The expression of mRNA for receptor subunits previously implicated in IL-4 and IL-13 signaling was investigated by reverse transcriptase-polymerase chain reaction. IL-13R, IL-13Ralpha, and IL-4Ralpha mRNA were repeatedly detected in hOBs, whereas mRNA for IL-2Rgamma(C) was not detected. Receptor-blocking antibodies to IL-4Ralpha inhibited the induction of IL-6 formation by both IL-4 and IL-13, indicating that both cytokines utilize this receptor subunit in signaling. However, the antibodies did not affect the IL-4/-13-induced inhibition of [(3)H]-thymidine incorporation or the stimulation of alkaline phosphatase (ALP), suggesting that IL-4Ralpha does not mediate these effects of IL-4/-13 in hOBs. We conclude that the cytokines IL-13 and IL-4, through sharing of receptor components, induce similar effects on hOBs, causing inhibition of cell proliferation, stimulation of IL-6, and enhanced ALP activity.

Epidermal growth factor regulates astrocyte expression of the interleukin-4 receptor via a MAPK-independent pathway

Human astrocytes express the interleukin (IL)-4 receptor alpha chain (IL-4R alpha) in vitro and in vivo but mechanisms governing astrocyte IL-4R alpha expression have not been established. We hypothesized that epidermal growth factor (EGF) and IL-4, agents that profoundly affect astrocyte proliferation, might also alter IL-4R alpha expression. Exposure to EGF for 24 h enhanced IL-4R alpha mRNA levels; in contrast, IL-4 yielded no increase. Immunoblotting demonstrated that EGF but not IL-4 increased astrocyte IL-4R alpha protein after 2--4 days of exposure. Similarly, EGF but not IL-4 strongly activated phosphorylation of p42/p44 extracellular regulated kinase isoforms, a reaction blocked by the mitogen-activated protein kinase (MAPK) inhibitor, PD98059. PD98059 also blocked EGF-stimulated DNA synthesis but not IL-4R alpha mRNA levels, while antibody to the EGF receptor (erbB1) blocked both EGF effects. Data suggest that astrocyte IL-4R alpha expression is upregulated by EGF but not by IL-4 in an EGF-receptor-dependent manner and that mechanisms are independent of MAPK activation.

Glucocorticoids upregulate CD40 ligand expression and induce CD40L-dependent immunoglobulin isotype switching

IL-4 and CD40 ligation are essential for IgE synthesis by B cells. We have shown previously that hydrocortisone (HC) induces IgE synthesis in IL-4-stimulated human B cells. In this study we demonstrate that HC fails to induce IgE synthesis in B cells from CD40 ligand-deficient (CD40L-deficient) patients. Disruption of CD40L-CD40 interactions by soluble CD40-Ig fusion protein or anti-CD40L mAb blocked the capacity of HC to induce IgE synthesis in normal B cells. HC upregulated CD40L mRNA expression in PBMCs and surface expression of CD40L in PBMCs as well as in purified populations of T and B cells. Upregulation of CD40L mRNA in PBMCs occurred 3 hours after stimulation with HC and was inhibited by actinomycin D. Upregulation of CD40L mRNA and induction of IgE synthesis by HC were inhibited by the steroid hormone receptor antagonist RU-486. These results indicate that ligand-mediated activation of the glucocorticoid receptor upregulates CD40L expression in human lymphocytes.

Characterization of IL-4 receptor components expressed on monocytes and monocyte-derived macrophages: variation associated with differential signaling by IL-4

The anti-inflammatory effects of IL-4 on activated monocytes differ from those on monocyte-derived macrophages (MDMac). While IL-4 suppresses LPS-induced IL-1beta , IL-12, IL-10 and TNFalpha production by monocytes, IL-4 suppresses only IL-1beta and IL-12 production by MDMac. The U937 and Mono Mac 6 cell lines have similar cytokine responses to IL-4 as monocytes and MDMac, respectively. The IL-4Ralpha and IL-2Rgamma (gammac) chains are well-characterized components of the IL-4 receptor. Cross-linking studies with 125I-IL-4 revealed that for monocytes and U937 cells, the binding of IL-4 to the receptor components was approximately 1:1 for IL-4Ralpha:gammac. In contrast, for MDMac and Mono Mac 6 cells that have a relative reduction in gammac surface expression, the binding of IL-4 to IL-4Ralpha:gammac was approximately 3:1. Furthermore, IL-4 induced IL-4Ralpha chain phosphorylation more rapidly in MDMac and Mono Mac 6 cells than in monocytes and U937 cells. This study identifies a correlation between altered 125I-IL-4 cross-linking to IL-4Ralpha:gammac, IL-4-induced signaling and regulation of pro-inflammatory cytokine production by IL-4.

Type 1/Type 2 immunity in infectious diseases

T helper type 1 (Th1) lymphocytes secrete secrete interleukin (IL)-2, interferon-gamma, and lymphotoxin-alpha and stimulate type 1 immunity, which is characterized by intense phagocytic activity. Conversely, Th2 cells secrete IL-4, IL-5, IL-9, IL-10, and IL-13 and stimulate type 2 immunity, which is characterized by high antibody titers. Type 1 and type 2 immunity are not strictly synonymous with cell-mediated and humoral immunity, because Th1 cells also stimulate moderate levels of antibody production, whereas Th2 cells actively suppress phagocytosis. For most infections, save those caused by large eukaryotic pathogens, type 1 immunity is protective, whereas type 2 responses assist with the resolution of cell-mediated inflammation. Severe systemic stress, immunosuppression, or overwhelming microbial inoculation causes the immune system to mount a type 2 response to an infection normally controlled by type 1 immunity. In such cases, administration of antimicrobial chemotherapy and exogenous cytokines restores systemic balance, which allows successful immune responses to clear the infection.

NKT cell-mediated repression of tumor immunosurveillance by IL-13 and the IL-4R-STAT6 pathway

Using a mouse model in which tumors show a growth-regression-recurrence pattern, we investigated the mechanisms for down-regulation of cytotoxic T lymphocyte-mediated tumor immunosurveillance. We found that interleukin 4 receptor (IL-4R) knockout and downstream signal transducer and activator of transcription 6 (STAT6) knockout, but not IL-4 knockout, mice resisted tumor recurrence, which implicated IL-13, the only other cytokine that uses the IL-4R-STAT6 pathway. We confirmed this by IL-13 inhibitor (sIL-13R alpha 2-Fc) treatment. Loss of natural killer T cells (NKT cells) in CD1 knockout mice resulted in decreased IL-13 production and resistance to recurrence. Thus, NKT cells and IL-13, possibly produced by NKT cells and signaling through the IL-4R-STAT6 pathway, are necessary for down-regulation of tumor immunosurveillance. IL-13 inhibitors may prove to be a useful tool in cancer immunotherapy.

Mucosal immunity against parasitic gastrointestinal nematodes

The last two decades witnessed significant advances in the efforts of immunoparasitologists to elucidate the nature and role of the host mucosal defence mechanisms against intestinal nematode parasites. Aided by recent advances in basic immunology and biotechnology with the concomitant development of well defined laboratory models of infection, immunoparasitologists have more precisely analyzed and defined the different immune effector mechanisms during the infection; resulting in great improvement in our current knowledge and understanding of protective immunity against gastrointestinal (GI) nematode parasites. Much of this current understanding comes from experimental studies in laboratory rodents, which have been used as models of livestock and human GI nematode infections. These rodent studies, which have concentrated on Heligmosomoides polygyrus, Nippostrongylus brasiliensis, Strongyloides ratti/S. venezuelensis, Trichinella spiralis and Trichuris muris infections in mice and rats, have helped in defining the types of T cell responses that regulate effector mechanisms and the effector mechanisms responsible for worm expulsion. In addition, these studies bear indications that traditionally accepted mechanisms of resistance such as eosinophilia and IgE responses may not play as important roles in protection as were previously conceived. In this review, we shall, from these rodent studies, attempt an overview of the mucosal and other effector responses against intestinal nematode parasites beginning with the indices of immune protection as a model of the protective immune responses that may occur in animals and man.

Cutting edge: spontaneous rejection of poorly immunogenic P1.HTR tumors by Stat6-deficient mice

Experimental evidence suggests that a type 1 T cell response may result in optimal tumor rejection in vivo. This phenotype is determined in part by cytokines that influence T cell differentiation. In transplantable tumor models such as P1.HTR, tumors grow progressively despite expression of defined tumor Ags. We hypothesized that this failure to reject may be due to poor generation of a type 1 phenotype, through a dominant influence of the type 2-promoting cytokines IL-4 and/or IL-13. This hypothesis was tested by implanting P1.HTR tumors into mice deficient in Stat6. In contrast to progressive growth of P1.HTR tumors in wild-type mice, and aggressive growth even of IL-12-transfected P1.HTR in Stat1(-/-) mice, P1.HTR was spontaneously rejected by Stat6(-/-) mice. Rejection was accompanied by augmented tumor-specific IFN-gamma production and CTL activity. These results suggest that pharmacologic inhibition of Stat6 signaling could potentiate anti-tumor immunity in vivo.

The activity of soluble VCAM-1 in angiogenesis stimulated by IL-4 and IL-13

IL-13 is a multifunctional lymphokine sharing a number of biological properties with IL-4. We previously observed that IL-4 shows angiogenic activities in vitro as well as in vivo. In this study we examined the effect of IL-13 on angiogenesis in vitro and in vivo and also the underlying mechanisms. Human IL-13 significantly stimulated the formation of tube-like structures in collagen gels by human microvascular endothelial cells and bovine aortic endothelial cells by about 3-fold over the controls in the absence of the cytokines. Administration of murine IL-13 led to neovascularization when implanted in the rat cornea. Coadministration of neutralizing mAb to the IL-4R inhibited both tubular morphogenesis in vitro and activation of STAT6 induced by IL-4 or IL-13. Both IL-4 and IL-13 markedly increased mRNA levels of VCAM-1 in vascular endothelial cells, and the production of the soluble form of VCAM-1 was also stimulated in response to IL-4 or IL-13. Administration of anti-VCAM-1 Ab in vitro blocked tubular morphogenesis induced by IL-4 and IL-13. Angiogenesis induced in vivo in rat cornea by IL-4 and IL-13 was also inhibited by Ab against the rat alpha4 integrin subunit. These findings suggest that angiogenesis dependent on IL-4 and IL-13 is mainly mediated through a soluble VCAM-1/alpha4 integrin pathway.

IL-4/IL-13 signaling beyond JAK/STAT

In the past several years, extensive studies on the mechanisms underlying IL-4 and IL-13 signaling have enabled us to gain insight into how these cytokines regulate immune responses. Because both IL-4 and IL-13 use the IL-4Ralpha as a receptor component, these cytokines activate many common signaling pathways. Both of these cytokines use Janus kinases (JAKs) to initiate signaling and activate signal transducer and activator of transcription-6 (STAT6), which is a transcription factor required for many of their biologic functions. In addition to JAK/STAT, these cytokines also activate a variety of other signaling molecules that are important in regulating IL-4-induced proliferation and protection from apoptosis. Suppressor of cytokine signaling-1 (SOCS-1) is a molecule that can inhibit the activation of IL-4 signaling through the inhibition of JAKs. The Fes tyrosine kinase is activated by IL-4 and appears to be important in regulating IL-4-induced proliferation through the phosphorylation of insulin receptor substrate (IRS) molecules. IRS molecules are essential for IL-4-induced proliferation through their ability to recruit phosphoinositol-3 kinase to the activated IL-4 receptor kinase. In addition, IL-4 can activate a number of phosphatases including SH2-containing inositol phosphatase (SHIP), SHP-1, and SHP-2. Finally, B-cell lymphoma gene-6 (BCL-6) appears to regulate a subset of IL-4-induced genes. Thus the biologic responses induced by IL-4/IL-13 require a complex interaction of signaling pathways and regulators.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

The biology of Stat4 and Stat6

IL-4 and IL-12 are cytokines that are important regulators of the proliferation, differentiation and functional capacity of lymphocytes. STATs (signal transducers and activators of transcription) are transcription factors that provide a direct link between the cytokine receptors and cytokine induced gene transcription. Stat6 and Stat4 are two STAT family members that specifically mediate signals that emanate from the IL-4 and IL-12 receptors, respectively. Recently a great deal of progress has been made in understanding the specific roles that Stat6 and Stat4 play in lymphocyte function through in vitro as well as in vivo studies using Stat6 and Stat4-deficient mice. This report will summarize and describe the recent advances made in understanding the activation and regulation of Stat6 and Stat4 as well as their roles in the development of an immune response. Oncogene (2000).