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Transgenic Modeling of Interleukin-13 in the Lung^*

^* From the Departments of Internal Medicine (Drs. Elias, Zheng, Lee, Chen, Ma, and Zhu), Section of Pulmonary and Critical Care Medicine, and Pathology (Dr. Homer), Yale University School of Medicine, New Haven, CT; and the Department of Biochemistry and Molecular Biology (Dr. Blackburn), University of Texas Health Science Center, Houston Medical School, Houston, TX 77030.

Correspondence to: Jack A. Elias, MD, Section of Pulmonary and Critical Care Medicine, Yale University School of Medicine, Department of Internal Medicine, 333 Cedar St, LCI 105, New Haven, CT 06520-8057.

	Abstract

TOP Abstract Introduction Materials and Methods Conclusions References

 
Interleukin (IL)-13 is a key cytokine in asthma pathogenesis. We used constitutive and inducible overexpression transgenic mice to characterize the mechanisms by which IL-13 causes phenotypic alterations in the lung. These studies demonstrated that chemokine receptor-2, transforming growth factor-ß₁, and IL-11 play an important role in the regulation of inflammation and remodeling in the IL-13-treated lung. The study results also demonstrated that IL-13 induces vascular endothelial growth factor, which causes bronchial circulation neovascularization in the murine airway. Last, it was demonstrated that IL-13 induces adenosine accumulation and that adenosine in turn stimulates IL-13 elaboration. These approaches validated in vivo genetic targets against which therapies can be directed to selectively regulate aspects of the IL-13 phenotype.

Key Words: adenosine • airway remodeling • interleukin-11 • interleukin-13 • transforming growth factor-ß₁ • vascular endothelial growth factor

	Introduction

TOP Abstract Introduction Materials and Methods Conclusions References

 
Asthmatic airways dysfunction used to be considered largely in terms of the contraction of airways smooth muscle (bronchospasm). However, numerous studies have prompted an appreciation of the central role of inflammation in this disorder. These studies also have demonstrated that T helper (Th) type 2 cells and their cytokine mediators likely play a central role in this disorder via the initiation and maintenance of airway inflammation, the regulation of B-cell and eosinophil function, the induction of mucus responses, and the stimulation of airway remodeling.¹

In addition to inflammation, structural alterations (variously referred to as airway remodeling) exist in the asthmatic airway. These alterations are thought to be caused by asthmatic inflammation and have been demonstrated, in modeling studies, to be able to contribute to the symptoms and physiologic dysregulation characteristic of the asthmatic diathesis. Thus, a full understanding of asthma pathogenesis requires not only an understanding of the mechanisms of inflammation but also the paradigms of injury and wound healing in the airway. Airway wall thickening, subepithelial fibrosis, mucus metaplasia, myofibroblast hyperplasia, myocyte hyperplasia and hypertrophy, epithelial hypertrophy, and an increase in the number and size of superficial blood vessels are prominent features of asthmatic airway remodeling.² Most studies, but not all, have suggested that airway fibrosis contributes to disease severity, to the generation of airways hyperresponsiveness, and, in some patients, to incompletely irreversible airways obstruction. The cellular and molecular events, however, that are responsible for the remodeling responses have not been adequately defined.

Interleukin (IL)-13 is a product of a gene on chromosome 5 at q31 that is produced in large quantities by appropriately stimulated CD4+ Th2 cells. IL-13 was originally described as an IL-4-like molecule and was noted to stimulate IgE production, CD23 expression, endothelial cell P-selectin, and vascular cell adhesion molecule-1 expression and to activate B cells. More recent studies have implicated IL-13 in the generation of mucus metaplasia,^{3 4 5} the regulation of eosinophil apoptosis, and the induction of airway remodeling.² The exaggerated production of IL-13 is well-documented in patients with atopic and nonatopic asthma,^{6 7 8} and polymorphisms of the IL-13 promoter and coding regions have been associated with asthma in study populations. IL-13 also plays an important role in the pathogenesis of type II granulomatous responses, idiopathic pulmonary fibrosis, scleroderma, and nodular sclerosing Hodgkin disease. However, the mechanisms by which IL-13 mediates its profound tissue effect have not been fully defined.

We hypothesized that a true picture of the effector properties of IL-13 and an in-depth understanding of the mechanisms that are responsible for these effector pathways could be obtained using overexpression transgenic approaches. To test this hypothesis, we developed constitutive, inducible, and "tight" on/off, triple transgenic systems that allowed IL-13 and/or other cytokines to be constitutively expressed and expressed in a temporally regulated fashion in the murine lung. Analyses of these transgenic animals have provided impressive insights into the pathways that IL-13 uses to generate its pulmonary effects. The systems and selected pathways are summarized below.

	Materials and Methods

TOP Abstract Introduction Materials and Methods Conclusions References

 
Constitutive Overexpression Transgenic Modeling
The methods that were used to generate mice in which IL-13 or IL-11 was constitutively overexpressed in the murine airway using the Clara cell-10-kd (CC10) protein promoter have been described previously.^{5 9}

Inducible Overexpression Transgenic Modeling of IL-13 The methods that were used to generate and characterize transgenic mice (ie, CC10-reverse tetracycline transactivator [rtTA]-cytokine mice) in which IL-13 or IL-11 was inducibly targeted to the airway have been described.^{10 11}

Generation of Tight Tetracycline-Controlled Transcriptional Suppressor-Based Triple Transgenic Mice Expressing IL-13 To be able to generate mice in which the IL-13 transgene can be turned on or off in the airway (ie, CC10-tetracycline-controlled transcriptional suppressor [tTS]-rtTA-IL-13 mice), the tTS system was employed, as described by our laboratory.¹² The methods that were used to generate these animals and to characterize their phenotype also have been described.^{11 12}

Results and Discussion
Constitutive Overexpression Transgenic Modeling of IL-13 With CC10-IL-13 Mice To begin to characterize the in vivo effector functions of IL-13, the construct CC10-IL-13-human growth hormone (hGH) was prepared, which contained the CC10 promoter, murine IL-13 complementary DNA, and hGH intronic and polyadenylation sequences.⁵ Standard pronuclear microinjection was undertaken, founder animals were identified, and the phenotypes of transgene (+) and (-) littermate controls were compared.

Histologic Analysis In contrast to transgene (-) littermates, the lungs from transgene (+) mice contained an eosinophil-rich, lymphocyte-rich, and macrophage-rich inflammatory response around small and large airways and in nearby parenchyma. Epithelial hypertrophy was also prominent in the conducting and small airways. Alveolar wall rupture, airspace enlargement, and focal organization of crystalline material into Masson body-like fibrotic foci also were appreciated.

Effect on Airway Mucus At all time points, cells stained with periodic acid-Schiff and/or Alcian blue stain were not seen in the airways of transgene (-) animals. In contrast, cells stained with periodic acid-Schiff and Alcian blue stains were prominent in the airways of transgene (+) animals. IL-13 was also a potent inducer of airway mucin (MUC) gene expression.

IL-13 Induction of Tissue Fibrosis Masson trichrome stains and hydroxyproline assays were also used to evaluate the amount of collagen in lungs from transgene (-) and (+) animals. A small amount of blue-stained collagen could be seen in and near the airway wall, and loosely packed collagen could be seen in the bronchovascular bundles of transgene (-) mice. In contrast, enhanced collagen deposition was readily appreciated in the subepithelial region and in the adventitia of the small and large airways of the transgenic animals. Striking increases in hydroxyproline content were seen in 3-month-old transgene (+) mice. In all cases, immunohistochemistry revealed increases in types I and III, but not type IV collagen. Immunohistochemistry also did not reveal an increase in -smooth muscle actin (+) cells.

Effect on Airway Physiology The baseline airways resistance of transgene (+) animals was mildly elevated when high levels of IL-13 were produced. Transgene (+) mice also manifested airways hyperresponsiveness in response to methacholine challenge using invasive and noninvasive enhanced pause (Penh) assessment methodologies.

Externally Regulatable Transgenic Modeling: General Concepts
The standard lung-targeted overexpression transgenic approach has provided remarkable insights into pulmonary biology.^{10 11} It does, however, have a number of limitations that result from the fact that the CC10 (and surfactant protein-C) promoters that are used most frequently are activated in utero and drive gene expression in a constitutive fashion thereafter. This system is limited in its ability to model waxing-and-waning disease processes (such as asthma). It also confounds phenotypic interpretation by superimposing growth-related and/or development-related abnormalities on abnormalities caused by the gene product in the adult animal. The developmental issue is of particular relevance to the analysis of alveolar enlargement in transgenic models such as that seen in the CC10-IL-13 mice. The normal mouse is not born with true alveoli. They are instead born with large alveolar sacs, which become alveoli over the first month of life via a process that involves growth and septation. Similarly, humans are born with 15% of their adult alveoli and grow additional alveoli over the first 3 to 4 years of life. Thus, alveolar enlargement in mice (and humans) can be caused by processes that block development (as in broncho-pulmonary dysplasia) and/or processes that destroy normally formed adult lung tissue (as in cigarette-induced emphysema).

In an attempt to overcome the limitations of traditional overexpression transgenics, we developed a lung-specific overexpression system in which transgene expression can be externally regulated. This system is based on the generation of mice with two transgenic constructs. The CC10-rtTA-hGH construct (construct 1) contains the CC10 promoter, the rtTA, and hGH intronic nuclear localization and polyadenylation sequences. The rtTA is a fusion protein made up of a mutated tetracycline operator (tet-O)-binding protein and the herpes virus VP-16 transactivator. The second construct, called tet-O-CMV-cytokine, contains a polymeric tet-O, minimal cytomegalovirus (CMV) promoter, the cytokine gene of interest, and hGH. In this system, the CC10 promoter directs the expression of rtTA to the lung. In the presence of doxycycline (dox) [which is added to the animal’s drinking water], rtTA binds, in trans, to the tet-O, and VP-16 activates the transgene. In the absence of dox, rtTA binding does not occur or occurs only at a low level and the transgenic construct is not activated or is transcribed at low levels.

Inducible Modeling of CC10-rtTA-IL-13 Mice
The construct tet-O-CMV-IL-13, which contains the murine IL-13 complementary DNA and the CC10-rtTA-hGH construct, were prepared and microinjected simultaneously. Appropriately, transgene (+) mice were identified and randomized to receive normal water or dox water at 1 month of age. In the absence of dox, levels of IL-13 75 pg/mL were noted in BAL fluids from dual transgene (+) mice. In transgene (+) mice, steady-state levels of IL-13 between 0.3 and 1.5 ng/mL were seen within 96 h of dox administration.

Histologic Characterization In dual-transgene (+) animals, dox-induced IL-13 elaboration caused impressive inflammatory and structural alterations. The inflammation was prominent in BAL fluids in which as little as 7 days of dox-induced IL-13 caused a 7.5-fold increase in BAL cell recovery and a striking increase in the percentage of BAL cells that were eosinophils. Lymphocyte and macrophage recovery also was increased (p < 0.01 for both). Mononuclear, lymphocytic, and eosinophilic infiltrates were also prominent in airway and peribronchial structures. IL-13 induction also caused an impressive increase in airway mucus metaplasia and impressive increases in the levels of messenger RNA encoding MUC-5AC, MUC-2, and MUC-4. When dox was administered in the long term, subepithelial fibrosis and crystal deposition could be seen. In addition, when a pressure fixation method was used that relied on pulmonary compliance, alveolar and lung enlargements were seen. This is compatible with the onset of true emphysema and, possibly, with the pseudoemphysema that has been described in patients with chronic asthma.¹³

IL-13 Induction of Pulmonary Inflammation
In all of the IL-13 transgenic mice, IL-13 induced an eosinophil-rich, macrophage-rich, and lymphocyte-rich pulmonary inflammatory response. To obtain insight into the mechanisms that might be responsible for this response, studies were undertaken to determine whether IL-13 induced C-C chemokines in these animals. Reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, in situ hybridization, and/or Northern blot evaluations demonstrated that IL-13 is a powerful inducer of eotaxin-1, eotaxin-2, monocyte chemotactic protein (MCP)-1, MCP-2, MCP-3, MCP-5, macrophage inflammatory protein (MIP)-1, MIP-1ß, C10, monocyte-derived chemokine, thymus and activation-regulated chemokine, thymus-expressed chemokine, MIP-3, and KC. The levels of induction of MCP-1, eotaxin-1, and C10 were particularly powerful. Because of the large number of chemokines that were induced by IL-13, studies were next undertaken to determine whether any of these inductive events played a key role in the generation of the IL-13-induced phenotype. The interaction of MCP-1 and its receptor, chemokine receptor (CCR) 2, was chosen for these studies because MCP-1 was one of the earliest chemokines that was induced by IL-13. In these studies, IL-13 transgenic mice were bred with mice with wild-type (+/+) or null mutant (-/-) CCR2 loci, and the effects of IL-13 in the presence and absence of CCR2 were compared. These studies demonstrated that CCR2 signaling plays a critical role in the generation the IL-13-induced phenotype because transgenic mice that were deficient in CCR2 had markedly diminished tissue inflammation, decreased BAL cellularity (without a change in the BAL cell differential), decreased lung size, decreased pulmonary compliance, decreased alveolar size, and diminished subepithelial collagen accumulation. The latter were due, at least in part, to the decreased ability of IL-13 to stimulate the production of transforming growth factor (TGF)-ß₁ in this setting (see below).

IL-13 Regulation of Collagen Accumulation and TGF-ß₁ Elaboration
The studies noted above demonstrated that IL-13 is a potent stimulator of subepithelial and adventitial airway fibrosis. To identify the mechanisms by which IL-13 induces tissue fibrosis, studies were undertaken to determine whether IL-13 could regulate the elaboration and/or activation of TGF-ß₁. These studies¹⁴ demonstrated that IL-13 is a potent and selective inducer of messenger RNA encoding TGF-ß₁. They also demonstrated that the BAL fluid from IL-13 transgenic animals contain exaggerated levels of bioactive TGF-ß as well as total TGF-ß. The results of immunohistochemistry and in situ hybridization demonstrated that TGF-ß₁ could be found in and is produced in epithelial cells from transgene (-) animals and in epithelial cells, macrophages, eosinophils, and type II cells from IL-13 transgenic mice.

Since TGF-ß₁ is elaborated as a biologically inactive promolecule that must be activated in vivo to mediate its biological effects, studies were undertaken to define the mechanisms of TGF-ß₁ activation in our transgenic mice. In these studies, RT-PCR was used to evaluate a variety of systems that have been implicated in the activation of TGF-ß₁. Significant differences were noted only in the levels of messenger RNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. To gain insight into the role of MMP-9 in this process, IL-13 transgenic mice were crossed with mice with a null mutation of MMP-9, and the levels of bioactive TGF-ß₁ in BAL fluid from IL-13-producing transgenic animals with wild-type and (-/-) MMP-9 loci were compared. These studies demonstrated that a deficiency of MMP-9 markedly diminished TGF-ß₁ activation but did not diminish the elaboration of TGF-ß₁ in this system. A similar decrease in TGF-ß₁ activation was seen after treatment with aprotinin, which blocks the plasmin/plasminogen system. When viewed in combination, these studies have demonstrated that MMP-9 and the plasmin/plasminogen system play critical roles in IL-13-induced TGF-ß₁ activation.

To determine whether IL-13-induced tissue fibrosis was mediated by TGF-ß₁, we compared the fibrotic responses in IL-13-overexpressing transgenic mice that were treated with a soluble TGF-ß antagonist (ie, sTGF-ß R-Fc) or an appropriate control. These studies demonstrated that the fibrotic effects of IL-13 are mediated, in great extent, by TGF-ß because they were almost completely abrogated by this treatment.

Last, studies were undertaken to determine whether the mechanisms of activation of TGF-ß₁ that were defined in our transgenic mice also contribute to the induction of tissue fibrosis. In these experiments, we compared the fibrotic responses induced by IL-13 in MMP-9-sufficient mice, in MMP-9-deficient mice, and in mice treated with aprotinin. In all cases, interventions that blocked TGF-ß₁ activation caused significant decreases in tissue fibrosis. This demonstrates that these activation pathways are involved in IL-13-induced fibrosis in our transgenic animals.

Use of the Tight tTS Transgenic System to Overexpress Bioactive TGF-ß₁
To fulfill the postulates of Koch regarding TGF-ß₁, we wanted to demonstrate that TGF-ß₁ can produce subepithelial fibrosis and other features of airway remodeling when it is chronically overexpressed in the murine airway. Prior attempts to overexpress transgenic TGF-ß₁ in the lung have not been successful because the CC10 and surfactant protein-C promoters activate the TGF-ß₁ transgene in utero and TGF-ß₁ blocks lung development, causing fetal lethality.¹⁵ To address this problem, we have developed a novel, completely new, triple-transgenic system that allows an investigator to selectively overexpress developmentally toxic transgenes in the adult animal. This transgenic system utilizes construct 1 (CC10-rtTA-hGH) and construct 2 (tet-O-CMV-cytokine x), which were described above. The third construct has the CC10 promoter driving the expression of the tTS. The tTS is a fusion protein made up of a modified tet-O-binding protein and the KRAB-AB domain of the potent kid-1 protein, which is a powerful suppresser of gene transcription.¹² As illustrated in Figure 1 , in the absence of dox, tTS binds to and suppresses the expression of all tet-O-regulated genes. In the presence of dox, tTS is released, allowing the activating, dox-binding, rtTA to bind to the tet-O and to activate transgene expression. To generate triple-transgenic CC10-rtTA-tTS-TGF-ß mice, the three constructs were generated. To be sure that the transgenic TGF-ß₁ that was produced was bioactive, we removed the sequences encoding the TGF-ß₁ propeptide from our cytokine complementary DNA. The constructs then were pooled and were simultaneously microinjected. Multiple lines of triple-transgenic mice were generated and utilized. In the absence of dox administration, lungs from these mice were normal in appearance. In contrast, as little as 10 days of treatment with dox caused significant TGF-ß₁ production and a robust remodeling response with subepithelial fibrosis and myocyte and myofibroblast hyperplasia. These studies demonstrate that TGF-ß₁ is able to reproduce many of the key features of the remodeling response in the asthmatic airway.

View larger version (20K): [in this window] [in a new window] [Download PPT slide]   Figure 1.. Triple transgenic system showing the binding of tTS in the absence of dox and the release of tTS and binding of rtTA in the presence of dox.

View larger version (18K): [in this window] [in a new window] [Download PPT slide]   Figure 2.. Proposed positive feedback loop involving IL-13, adenosine and adenosine R.

IL-11: An Endogenous Regulator of IL-13-Induced Inflammation and Fibrosis
IL-11 is a cytokine of the IL-6 family that is produced by a variety of structural cells in the lung including fibroblasts and epithelial cells. Previous studies from our laboratory demonstrated that transgenic IL-11 causes subepithelial airway fibrosis⁹ and inhibits Th2 inflammatory responses in the lung.¹⁹ To determine whether IL-13 and IL-11 interact in the generation of the IL-13 phenotype, studies were undertaken to determine whether IL-13 regulated the levels of expression of IL-11 or its receptor in pulmonary tissues. These studies demonstrated that IL-11 and IL-11 receptor (R) are both prominently induced in lungs from IL-13 transgenic mice. To evaluate the role that IL-11 plays in this system, IL-13 transgenic mice were bred with mice with (1) a null mutation of IL-11R and (2) mice that overexpressed IL-11 in the lung. These studies demonstrated that a deficiency of IL-11R decreased the IL-13-induced inflammatory response, and that the simultaneous elaboration of IL-11 and IL-13 caused a synergistic increase in airway fibrosis. When viewed in combination, these studies demonstrated that IL-11 is an important mediator of airway remodeling and an important endogenous regulator of IL-13-induced tissue inflammation. Further support for the importance of these studies comes from evaluations performed in collaboration with Minshall and colleagues²⁰ that demonstrated that IL-11 is found in exaggerated quantities in airway epithelial cells and eosinophils from patients with severe asthma in whom IL-11 levels correlate inversely with FEV₁.

	Conclusions

TOP Abstract Introduction Materials and Methods Conclusions References

 
The studies noted above have given us a glimpse at the many mechanisms involved in IL-13-induced phenotype generation in the airway. As illustrated in Figure 3 , IL-13-induced chemokines acting via CCR2, and probably other receptors such as CCR1, play a critical role in the generation of inflammation and fibrosis. IL-13-induced IL-11 serves as an endogenous regulator of tissue inflammation and a stimulator of tissue fibrosis. IL-13 induction and activation of TGF-ß₁ is a major mechanism mediating IL-13-induced airway fibrosis. VEGF causes bronchial neovascularization and a superficial localization of airway blood vessels, and IL-13 induction of adenosine accumulation and regulation of ARs and ADA serves to further augment IL-13 production, and may generate a local inflammation amplification loop. Importantly, these studies have provided critical information about genetic targets against which therapies can be directed to selectively regulate different aspects of the IL-13 phenotype.

View larger version (31K): [in this window] [in a new window] [Download PPT slide]   Figure 3.. Mechanisms of IL-13-induced phenotype generation highlighting roles of adenosine, VEGF, TFG-ß MMPs, IL-11, and chemokines.

	Footnotes

 
Abbreviations: ADA = adenosine deaminase; AR = adenosine receptor; CC10 = Clara cell-10-kd; CCR = chemokine receptor; CMV = cytomegalovirus; dox = doxycycline; hGH = human growth hormone; IL = interleukin; MCP = monocyte chemotactic protein; MIP = macrophage inflammatory protein; MMP = matrix metalloproteinase; MUC = mucin; R = receptor ; rtTA = reverse tetracycline transactivator; tet-O = tetracycline operator; TGF = transforming growth factor; Th = T helper; tTS = tetracycline-controlled transcriptional suppressor; VEGF = vascular endothelial growth factor

	References

TOP Abstract Introduction Materials and Methods Conclusions References

 

1. Ray, A, Cohn, L (1999) Th2 cells and GATA-3 in asthma: new insights into the regulation of airway inflammation. J Clin Invest 104,1001-1006[ISI][Medline]
2. Elias, JA, Zhu, Z, Chupp, G, et al Airway remodeling in asthma. J Clin Invest 1999;104,1001-1006[ISI][Medline]
3. Grünig, G, Warnock, M, Wakil, AE, et al Requirement for IL-13 independently of IL-4 in experimental asthma. Science 1998;282,2261-2263[Abstract/Free Full Text]
4. Wills-Karp, M, Luyimbazi, J, Xu, X, et al Interleukin-13: central mediator of allergic asthma. Science 1998;282,2258-2260[Abstract/Free Full Text]
5. Zhu, Z, Homer, RJ, Wang, Z, et al Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities and eotaxin production. J Clin Invest 1999;103,779-788[ISI][Medline]
6. Huang, SK, Xiao, HQ, Kleine-Tebbe, J, et al IL-13 expression at the sites of allergen challenge in patients with asthma. J Immunol 1995;155,2688-2694[Abstract]
7. Humbert, M, Durham, SR, Kimmitt, P, et al Elevated expression of messenger ribonucleic acid encoding IL-13 in the bronchial mucosa of atopic and nonatopic subjects with asthma. J Allergy Clin Immunol 1997;99,657-665[CrossRef][ISI][Medline]
8. Kotsimbos, TC, Ernst, P, Hamid, QA Interleukin-13 and interleukin-4 are coexpressed in atopic asthma. Proc Assoc Am Physicians 1996;108,368-373[ISI][Medline]
9. Tang, W, Geba, GP, Zheng, T, et al Targeted expression of IL-11 in the murine airway causes airways obstruction, bronchial remodeling and lymphocytic inflammation. J Clin Invest 1996;98,2845-2853[ISI][Medline]
10. Ray, P, Tang, W, Wang, P, et al Regulated overexpression of interleukin-11 in the lung: use to dissociate development-dependent and -independent phenotypes. J Clin Invest 1997;100,2501-2511[ISI][Medline]
11. Zheng, T, Zhu, Z, Wang, Z, et al Inducible targeting of IL-13 to the adult lung causes matrix metalloproteinase- and cathepsin-dependent emphysema. J Clin Invest 2000;106,1081-1093[ISI][Medline]
12. Zhu, Z, Ma, B, Homer, RJ, et al Use of the tetracycline-controlled transcriptional silencer (tTS) to eliminate transgene leak in inducible overexpression transgenic mice. J Biol Chem 2001;276,25222-25299[Abstract/Free Full Text]
13. Gelb, AF, Zamel, N Unsuspected pseudophysiologic emphysema in chronic persistent asthma. Am J Respir Cell Mol Biol 2000;162,1778-1782
14. Lee, CG, Homer, RJ, Zhu, Z, et al Interleukin-13 induces tissue fibrosis by selectively stimulating and activating TGF-ß₁. J Exp Med 2001;194,809-821[Abstract/Free Full Text]
15. Zhou, L, Dey, CR, Wert, SE, et al Arrested lung morphogenesis in transgenic mice bearing an SP-C-TGF-ß₁ chimeric gene. Dev Biol 1996;175,227-238[CrossRef][ISI][Medline]
16. Blackburn, MR, Volmer, JB, Thrasher, JL, et al Metabolic consequences of adenosine deaminase deficiency in mice are associated with defects in alveogenesis, pulmonary inflammation, and airway obstruction. J Exp Med 2000;192,159-170[Abstract/Free Full Text]
17. Chunn, JL, Young, HW, Banerjee, SK, et al Adenosine-dependent airway inflammation and hyperresponsiveness in partially adenosine deaminase-deficient mice. J Immunol 2001;167,4676-4685[Abstract/Free Full Text]
18. Corne, J, Chupp, G, Lee, CG, et al IL-13 stimulates vascular endothelial cell growth factor and protects against hyperoxic acute lung injury. J Clin Invest 2000;106,783-791[ISI][Medline]
19. Wang, JM, Homer, RJ, Hong, L, et al IL-11 selectively inhibits aeroallergen-induced pulmonary eosinophilia and Th2 cytokine production. J Immunol 2000;165,2222-2231[Abstract/Free Full Text]
20. Minshall, EM, Chakir, J, Laviolette, R, et al Interleukin-11 mRNA expression is increased in severe asthma: localization to eosinophils ;

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