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Experimental models in pulmonary pathology
Pathology (1995), 27, pp. 130-132
EXPERIMENTAL MODELS IN PULMONARY PATHOLOGY RAKESH K. KUMAR
School of Pathology, University of New South Wales, Sydney
Summary Because of the cellular complexity and spatial organization of the lung, investigation of the pathogenesis of human pulmonary diseases relies to a considerable extent upon the use of animal models. In this review, the author examines new models and new applications of existing models of pneumonia, asthma, emphysema, interstitial lung disease and neoplasms in laboratory mice and rats. Studies of such models may assist in the development of appropriate strategies for early diagnosis and intervention.
Key words: Animal models, pneumonitis, asthma, emphysema, interstitial lung disease. lung carcinoma. serum-free culture. Accepted 17 March 1995
Alexander Pope's assertion that "The proper study of mankind is man" 1 would surely be wholeheartedly endorsed by most readers of this journal. But mankind is frequently averse to being properly studied, especially when ill, which complicates investigation of the development and progression of human disease. Moreover, subclinical lesions are often not identifiable, or their assessment may be impracticable. Yet such assessment is frequently crucial to understanding pathogenesis and formulating appropriate strategies for early diagnosis and intervention. Thus there is a need for valid, informative experimental models which provide a sound scientific basis for devising these strategies. In vitro models are often useful for analyzing the contribution of individual cellular populations to a disease process. Various investigators have employed lung explants or slices in organ culture, relatively pure populations of cells dissociated from lung tissue, or cell lines adapted to long-term culture for in vitro studies of pulmonary cellular responses to injury. 2 The recent development of improved methods of serum-free primary culture, which permit the maintenance of a differentiated phenotype in vitro, has significantly enhanced the utility of such systems. 3 - 8 The lung, however, is a complex organ in which interactions between the many different types of specialized constituent cells are dependent upon their appropriate spatial organization. Furthermore, the effect of an injurious agent upon the lung is at least in part determined by the route of delivery of the agent in vivo. As a result, many critically important questions about the pathogenesis of lung and airway diseases can only be addressed through animal experimental studies. This brief review, from the perspective of an experimental pathologist, examines some interesting recent developments in the
design and application of relevant animal models of human pulmonary diseases. The author focuses in particular upon models in mice and rats, which offer a number of advantages to the experimentalist. Importantly, these rodents are bred expressly for laboratory use and specific pathogen-free animals are therefore readily available. The use of such animals is an essential prerequisite for reproducible studies of respiratory disorders.
Bacterial pneumonia Pneumococcal pneumonia continues to be a major clinical problem, yet until recently our understanding of its pathogenesis has been lamentably inadequate. Experimental studies in rats have now established that the thiolactivated pneumococcal toxin known as pneumolysin is able to trigger an intra-alveolar inflammatory response comparable to that elicited by viable organisms. 9 Furthermore, ex vivo studies in isolated perfused rat lungs indicate that this is a consequence of selective injury to the alveolar type 1 epithelium. 10 Pneumolysin may therefore have a crucial role in the pathogenesis of pneumonia and is a candidate antigen for the development of a protective immunization regimen. 9 ,10 Host factors are also important determinants of pneumococcal pneumonia. Recent reports of animal models in which increased susceptibility to pneumococcal pneumonia is associated with chronic ethanol ingestion l l or carbon tetrachloride-induced hepatic cirrhosis1 2 are comparable to the clinical situation and should permit further definition of some of these variables. Murine models of bacterial pneumonia continue to be used for evaluation of new therapeutic regimens. Studies published in the past few years include assessment of novel antimicrobial agents 13 and the use of colony stimulating factors to enhance neutrophil recruitment and thus improve the outcome of pneumonia complicating trauma and severe blood 108S. 14 Other pulmonary infections Chlamydia pneumoniae has recently been recognized as an important cause of respiratory infections in humans. Relatively little is known about infections caused by this organism, but the description of an animal model of chlamydial pneumonitis 15 should facilitate an understanding of its pathogenesis and lesions. Animal models of viral pneumonia have long been available. Of current interest is a report evaluating treatment with surfactant substitution in a Sendai virusinduced pneumonitis resembling the adult respiratory distress syndrome (ARDS).16
EXPERIMENTAL MODELS OF LUNG DISEASE
A particularly useful application of animal experimental models has been for the study of pneumonia caused by Pneumocystis carinii. This opportunistic pathogen cannot be grown in culture and thus an in vivo model of the disease is necessary. Improved models in both mice and rats have now been described 17 • 18 which may help in evaluating new therapeutic agents. Asthma Analysis of human bronchial biopsy specimens and bronchoalveolar lavage fluid has led to better definition of the early pathological changes in asthma. Meanwhile, studies of the pathogenesis of this common and complex disorder have been stimulated by the recent development of convenient and realistic models of allergic asthma in laboratory mice and rats. Animals sensitized to protein antigens, including antigens relevant to human allergic asthma, are subsequently challenged by inhalation of aerosolized antigen. 19-22 This triggers airway hyper-reactivity, as demonstrated by in vivo and in vitro studies, which is accompanied by inflammation in the bronchial wall. Experiments using strains of mice that exhibit cytokine deficiencies or other molecular lesions have already yielded new information about cellular mechanisms in asthmatic inflammation. 23 Emphysema Intriguing evidence in support of the protease-antiprotease hypothesis of the pathogenesis of emphysema has come from a recent study of "pallid" mice, an inbred strain with a genetic deficiency of al-antiprotease. 24 Adult animals develop emphysema which is correlated with a decreased content of lung elastin. To complicate the picture, however, emphysema has also been experimentally induced in transgenic mice with abnormal expression of collagenase in the lungs 25 and in these mice there is no evidence of elastic fibre destruction. Interstitial lung disease In most animal models of fibrogenic pulmonary injury, lesions are induced by a single exposure to a toxic agent and fibrosis develops over a relatively short period. These models are reminiscent of ARDS progressing to fibrosis but may be less relevant to chronic, progressive pulmonary fibrosis. Models have recently been described in which subacute inhalational exposure to irritants elicits a fibrotic response that more closely emulates lesions in humans. 26 •27 Experimental evidence is accumulating from these and related models to suggest that recruitment of activated Tlymphocytes plays an important pathogenetic role in pulmonary fibrosis. 27 - 29 There is less agreement about the role of these cells in hypersensitivity pneumonitis, with studies in different models producing quite divergent results. 3o •31 Neoplasms Spontaneously arising and carcinogen-induced pulmonary tumors in genetically susceptible mice have often been used as models of lung carcinoma, but their relevance remains controversial because these neoplasms at best resemble human bronchioloalveolar carcinoma. 32 Nevertheless, useful applications of such models in the evaluation of novel chemotherapeutic regimens continue to be described. 33
131
Potentially of greater interest is the development of xenograft models of human pulmonary neoplasms in immunodeficient mice. In a model in which dissociated cells from small cell carcinoma-derived lines were used to induce neoplasms in mice with severe combined immunodeficiency, the site of tumor growth was demonstrated to have a significant impact upon the efficacy of chemotherapeutic agents. 34 Clinically relevant patterns of response were noted with orthotopic pulmonary tumors but not with subcutaneously growing neoplasms derived from the same cells. Animal models of mesothelioma may be directly relevant to the human malignancy. The recently described complementary in vivolin vitro mouse model of mesothelioma is likely to provide a useful experimental system for studying the behavior of these tumors. 35 COMMENT
Relevant animal models of human respiratory disease continue to be devised and fruitfully applied to studies of pathogenesis, diagnosis and management. Clinical investigators sometimes disparagingly refer to those who study rodent models of disease as "mouse doctors" or the like, but such attitudes are unhelpful. The synergism of human and animal experimental research needs to be recognized by everyone in the interests of better medical science. Address for correspondence: R.K .K., School of Pathology, The University of New South Wales, Sydney, NSW 2052.
References
1. Pope A. An Essay on Man, Epistle 11. 1733.
2. Cohn LA, Adler KB. In vitro studies of mechanisms of lung injury in the rodent. Toxieol Pathol 1991; 19: 419-27. 3. Siminski JT, Kavanagh TJ, Chi E, Raghu G. Long-term maintenance of mature pulmonary parenchyma cultured in serum-free conditions. Am J Physiol 1992; 262: Ll05-10. 4. Kumar RK, O'Grady R, Li Wet al. Primary culture of adult mouse lung fibroblasts in serum-free medium: responses to growth factors. Exp Cell Res 1991; 193: 398-404. 5. Kawada H, Shannon JM, Mason RJ. Improved maintenance of adult rat alveolar type II cell differentiation in vitro: effect of serum-free, hormonally defined medium and a reconstituted basement membrane. Am J Respir Cell Mol Bioi 1990; 3: 33-43 .
6. Kumar RK, Li W, O'Grady R. Maintenance of differentiated phenotype by mouse type 2 pneumocytes in serum-free primary culture. Exp Lung Res 1995; 21: 79-94. 7. Yamaya M, Finkbeiner WE, Chun SY, Widdicombe JH. Differentiated structure and function of cultures from human tracheal epithelium. Am J Physiol 1992; 262: L713-24. 8. Kaartinen L, Nettesheim P, Adler KB, Randell SH. Rat tracheal epithelial cell differentiation in vitro. In Vitro Cell Dev Bioi 1993; 29A: 481-92. 9. Feldman C, Munro NC, Jeffery PK et al. Pneumolysin induces the salient histologic features of pneumococcal infection in the rat lung in vivo. Am J Respir Cell Mol BioI 1991; 5: 416-23. 10. Rubins JB, Duane PG, Clawson D et al. Toxicity of pneumolysin
to pulmonary alveolar epithelial cells. Infect Immun 1993; 61: 1352-8.
11. Davis CC, Mellencamp MA, Preheim LC. A model of pneumococcal pneumonia in chronically intoxicated rats. J Infect Dis 1991; 163: 799-805. 12. MeIJencamp MA, Preheim LC. Pneumococcal pneumonia in a rat model of cirrhosis: effects of cirrhosis on pulmonary defense mechanisms against Streptococcus pneumoniae. J Infect Dis 1991; 163: 102-8.
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KUMAR
13. Azoulay-Dupuis E, Vallee E, Veber B et aJ. In vivo efficacy of a new fluoroquinolone, sparfloxacin, against penicillin-susceptible and -resistant and multiresistant strains of Streptococcus pneumoniae in a mouse model of pneumonia. Antimicrob Agents Chemother 1992; 36: 2698-703. 14. Abraham E, Stevens P. Effects of granulocyte colony-stimulating factor in modifying mortality from Pseudomonas aeruginosa pneumonia after hemorrhage. CritCare Med 1992; 20: 1127-33. 15. Yang ZP, Kuo CC, Grayston IT. A mouse model of Chlamydia pneumoniae strain TWAR pneumonitis. Infect Immun 1993; 61: 2037-40. 16. van Daal GJ, Eijking EP, So KL et al. Acute respiratory failure during pneumonia induced by Sendai virus. Adv Exp Med Bioi 1992; 316: 319-26. 17. Powles MA, McFadden DC, Pittarelli LA, Schmatz DM. Mouse model for Pneumocystis carinii pneumonia that uses natural transmission to initiate infection. Infect lmmun 1992; 60: 1397-400.
Pathology (1995), 27, April 25. D'Armiento J, Dalal SS, Okada Y et aL Collagenase expression in the lungs of transgenic mice causes pulmonary emphysema. Cell 1992; 71: 955-61. 26. Last lA, Gelzleichter TR, Pinkerton KE et aL.A new model of progressive pulmonary fibrosis in rats. Am Rev Respir Dis 1993; 148: 487-94. 27. Velan GM, Kumar RK, Cohen DD. Pulmonary inflammation and fibrosis following subacute inhalational exposure to silica: determinants of progression. Pathology 1993; 25: 282-90. 28. Li W, Kumar RK, O'Grady R, Vel an GM. Role of Iymphocytes in silicosis: regulation of secretion of macrophage-derived mitogenic activity for fibroblasts. Int J Exp Pathol 1992; 73: 793-800. 29. Hu H, Stein-Streilein J. Hapten-immune pulmonary interstitial fibrosis (HIP IF) in mice requires both CD4 + and CD8 + T Iymphocytes. J Leuk Bioi 1993; 54: 414-22.
18. Boylan Cl, Current WL. Improved rat model of Pneumocystis carinii pneumonia: induced laboratory infections in Pneumocystisfree animals. Infect Immun 1992; 60: 1589-97.
30. Denis M, Cormier Y, Laviolette M, Ghadirian E. T cells in hypersensitivity pneumonitis: effects of in vivo depletion of T cells in a mouse model. Am J Respir Cell Mol BioI 1992; 6: 183-9.
19. Elwood W, Lotvall 10, Barnes Pl, Chung KF. Characterization of allergen-induced bronchial hyperresponsiveness and airway inflammation in actively sensitized Brown-Norway rats. 1 Allergy Clin Immunol 1991; 88: 951-60.
31. Takizawa H, Ohta K, Horiuchi T et al. Hypersensitivity pneumonitis in athymic nude mice: additional evidence of T cell dependency. Am Rev Respir Dis 1992; 146: 479-84.
20. Nagai H, Yamaguchi S, Ingagaki N et al. Effect of anti-IL-S monoclonal antibody on allergic responsiveness in mice. Life Sciences 1993; 53: PL243-7.
32. Gunning WT, Stoner GD, Goldblatt PJ. Glyceraldehyde-3phosphate dehydrogenase and other enzymatic activity in normal mouse lung and in lung tumors. Exp Lung Res 1991; 17: 255-61.
21. Renz H, Saloga 1, Bradley KL et al. Specific V/3 T cell subsets mediate the immediate hypersensitivity response to ragweed allergen. 1 Immunol1993; 151: 1907-17.
33. Belinsky SA, Stefanski SA, Anderson MW. The A/J mouse lung as a model for developing new chemointervention strategies. Cancer Res 1993; 53: 410-6.
22. Kung TT, lones H, Adams GK et al. Characterization of a murine model of allergic pulmonary inflammation. lnt Arch Allergy Appl Immunol 1994; 105: 83-90.
34. Kuo TH, Kubota T, Watanabe M et al. Site-specific chemosensitivity of human small-cell lung carcinoma growing orthotopically compared to subcutaneously in SCID mice: the importance of orthotopic models to obtain relevant drug evaluation data. Anticancer Res 1993; 13: 627-30.
23. Brusselle GG, Kips lC, Tavernier JH et al. Attenuation of allergic airway inflammation in IL-4 deficient mice. Clin Exp Allergy 1994; 24: 73-80. 24. Martorana PA, Brand T, Gardi C et aL The pallid mouse: A model of genetic ai-antitrypsin deficiency. Lab Invest 1993; 68: 233-41.
35. Davis MR, Manning LS, Whitaker D et al. Establishment of a murine model of malignant mesothelioma. Int J Cancer 1992; 52: 881-6.
EXPERIMENTAL MODELS IN PULMONARY PATHOLOGY RAKESH K. KUMAR
School of Pathology, University of New South Wales, Sydney
Summary Because of the cellular complexity and spatial organization of the lung, investigation of the pathogenesis of human pulmonary diseases relies to a considerable extent upon the use of animal models. In this review, the author examines new models and new applications of existing models of pneumonia, asthma, emphysema, interstitial lung disease and neoplasms in laboratory mice and rats. Studies of such models may assist in the development of appropriate strategies for early diagnosis and intervention.
Key words: Animal models, pneumonitis, asthma, emphysema, interstitial lung disease. lung carcinoma. serum-free culture. Accepted 17 March 1995
Alexander Pope's assertion that "The proper study of mankind is man" 1 would surely be wholeheartedly endorsed by most readers of this journal. But mankind is frequently averse to being properly studied, especially when ill, which complicates investigation of the development and progression of human disease. Moreover, subclinical lesions are often not identifiable, or their assessment may be impracticable. Yet such assessment is frequently crucial to understanding pathogenesis and formulating appropriate strategies for early diagnosis and intervention. Thus there is a need for valid, informative experimental models which provide a sound scientific basis for devising these strategies. In vitro models are often useful for analyzing the contribution of individual cellular populations to a disease process. Various investigators have employed lung explants or slices in organ culture, relatively pure populations of cells dissociated from lung tissue, or cell lines adapted to long-term culture for in vitro studies of pulmonary cellular responses to injury. 2 The recent development of improved methods of serum-free primary culture, which permit the maintenance of a differentiated phenotype in vitro, has significantly enhanced the utility of such systems. 3 - 8 The lung, however, is a complex organ in which interactions between the many different types of specialized constituent cells are dependent upon their appropriate spatial organization. Furthermore, the effect of an injurious agent upon the lung is at least in part determined by the route of delivery of the agent in vivo. As a result, many critically important questions about the pathogenesis of lung and airway diseases can only be addressed through animal experimental studies. This brief review, from the perspective of an experimental pathologist, examines some interesting recent developments in the
design and application of relevant animal models of human pulmonary diseases. The author focuses in particular upon models in mice and rats, which offer a number of advantages to the experimentalist. Importantly, these rodents are bred expressly for laboratory use and specific pathogen-free animals are therefore readily available. The use of such animals is an essential prerequisite for reproducible studies of respiratory disorders.
Bacterial pneumonia Pneumococcal pneumonia continues to be a major clinical problem, yet until recently our understanding of its pathogenesis has been lamentably inadequate. Experimental studies in rats have now established that the thiolactivated pneumococcal toxin known as pneumolysin is able to trigger an intra-alveolar inflammatory response comparable to that elicited by viable organisms. 9 Furthermore, ex vivo studies in isolated perfused rat lungs indicate that this is a consequence of selective injury to the alveolar type 1 epithelium. 10 Pneumolysin may therefore have a crucial role in the pathogenesis of pneumonia and is a candidate antigen for the development of a protective immunization regimen. 9 ,10 Host factors are also important determinants of pneumococcal pneumonia. Recent reports of animal models in which increased susceptibility to pneumococcal pneumonia is associated with chronic ethanol ingestion l l or carbon tetrachloride-induced hepatic cirrhosis1 2 are comparable to the clinical situation and should permit further definition of some of these variables. Murine models of bacterial pneumonia continue to be used for evaluation of new therapeutic regimens. Studies published in the past few years include assessment of novel antimicrobial agents 13 and the use of colony stimulating factors to enhance neutrophil recruitment and thus improve the outcome of pneumonia complicating trauma and severe blood 108S. 14 Other pulmonary infections Chlamydia pneumoniae has recently been recognized as an important cause of respiratory infections in humans. Relatively little is known about infections caused by this organism, but the description of an animal model of chlamydial pneumonitis 15 should facilitate an understanding of its pathogenesis and lesions. Animal models of viral pneumonia have long been available. Of current interest is a report evaluating treatment with surfactant substitution in a Sendai virusinduced pneumonitis resembling the adult respiratory distress syndrome (ARDS).16
EXPERIMENTAL MODELS OF LUNG DISEASE
A particularly useful application of animal experimental models has been for the study of pneumonia caused by Pneumocystis carinii. This opportunistic pathogen cannot be grown in culture and thus an in vivo model of the disease is necessary. Improved models in both mice and rats have now been described 17 • 18 which may help in evaluating new therapeutic agents. Asthma Analysis of human bronchial biopsy specimens and bronchoalveolar lavage fluid has led to better definition of the early pathological changes in asthma. Meanwhile, studies of the pathogenesis of this common and complex disorder have been stimulated by the recent development of convenient and realistic models of allergic asthma in laboratory mice and rats. Animals sensitized to protein antigens, including antigens relevant to human allergic asthma, are subsequently challenged by inhalation of aerosolized antigen. 19-22 This triggers airway hyper-reactivity, as demonstrated by in vivo and in vitro studies, which is accompanied by inflammation in the bronchial wall. Experiments using strains of mice that exhibit cytokine deficiencies or other molecular lesions have already yielded new information about cellular mechanisms in asthmatic inflammation. 23 Emphysema Intriguing evidence in support of the protease-antiprotease hypothesis of the pathogenesis of emphysema has come from a recent study of "pallid" mice, an inbred strain with a genetic deficiency of al-antiprotease. 24 Adult animals develop emphysema which is correlated with a decreased content of lung elastin. To complicate the picture, however, emphysema has also been experimentally induced in transgenic mice with abnormal expression of collagenase in the lungs 25 and in these mice there is no evidence of elastic fibre destruction. Interstitial lung disease In most animal models of fibrogenic pulmonary injury, lesions are induced by a single exposure to a toxic agent and fibrosis develops over a relatively short period. These models are reminiscent of ARDS progressing to fibrosis but may be less relevant to chronic, progressive pulmonary fibrosis. Models have recently been described in which subacute inhalational exposure to irritants elicits a fibrotic response that more closely emulates lesions in humans. 26 •27 Experimental evidence is accumulating from these and related models to suggest that recruitment of activated Tlymphocytes plays an important pathogenetic role in pulmonary fibrosis. 27 - 29 There is less agreement about the role of these cells in hypersensitivity pneumonitis, with studies in different models producing quite divergent results. 3o •31 Neoplasms Spontaneously arising and carcinogen-induced pulmonary tumors in genetically susceptible mice have often been used as models of lung carcinoma, but their relevance remains controversial because these neoplasms at best resemble human bronchioloalveolar carcinoma. 32 Nevertheless, useful applications of such models in the evaluation of novel chemotherapeutic regimens continue to be described. 33
131
Potentially of greater interest is the development of xenograft models of human pulmonary neoplasms in immunodeficient mice. In a model in which dissociated cells from small cell carcinoma-derived lines were used to induce neoplasms in mice with severe combined immunodeficiency, the site of tumor growth was demonstrated to have a significant impact upon the efficacy of chemotherapeutic agents. 34 Clinically relevant patterns of response were noted with orthotopic pulmonary tumors but not with subcutaneously growing neoplasms derived from the same cells. Animal models of mesothelioma may be directly relevant to the human malignancy. The recently described complementary in vivolin vitro mouse model of mesothelioma is likely to provide a useful experimental system for studying the behavior of these tumors. 35 COMMENT
Relevant animal models of human respiratory disease continue to be devised and fruitfully applied to studies of pathogenesis, diagnosis and management. Clinical investigators sometimes disparagingly refer to those who study rodent models of disease as "mouse doctors" or the like, but such attitudes are unhelpful. The synergism of human and animal experimental research needs to be recognized by everyone in the interests of better medical science. Address for correspondence: R.K .K., School of Pathology, The University of New South Wales, Sydney, NSW 2052.
References
1. Pope A. An Essay on Man, Epistle 11. 1733.
2. Cohn LA, Adler KB. In vitro studies of mechanisms of lung injury in the rodent. Toxieol Pathol 1991; 19: 419-27. 3. Siminski JT, Kavanagh TJ, Chi E, Raghu G. Long-term maintenance of mature pulmonary parenchyma cultured in serum-free conditions. Am J Physiol 1992; 262: Ll05-10. 4. Kumar RK, O'Grady R, Li Wet al. Primary culture of adult mouse lung fibroblasts in serum-free medium: responses to growth factors. Exp Cell Res 1991; 193: 398-404. 5. Kawada H, Shannon JM, Mason RJ. Improved maintenance of adult rat alveolar type II cell differentiation in vitro: effect of serum-free, hormonally defined medium and a reconstituted basement membrane. Am J Respir Cell Mol Bioi 1990; 3: 33-43 .
6. Kumar RK, Li W, O'Grady R. Maintenance of differentiated phenotype by mouse type 2 pneumocytes in serum-free primary culture. Exp Lung Res 1995; 21: 79-94. 7. Yamaya M, Finkbeiner WE, Chun SY, Widdicombe JH. Differentiated structure and function of cultures from human tracheal epithelium. Am J Physiol 1992; 262: L713-24. 8. Kaartinen L, Nettesheim P, Adler KB, Randell SH. Rat tracheal epithelial cell differentiation in vitro. In Vitro Cell Dev Bioi 1993; 29A: 481-92. 9. Feldman C, Munro NC, Jeffery PK et al. Pneumolysin induces the salient histologic features of pneumococcal infection in the rat lung in vivo. Am J Respir Cell Mol BioI 1991; 5: 416-23. 10. Rubins JB, Duane PG, Clawson D et al. Toxicity of pneumolysin
to pulmonary alveolar epithelial cells. Infect Immun 1993; 61: 1352-8.
11. Davis CC, Mellencamp MA, Preheim LC. A model of pneumococcal pneumonia in chronically intoxicated rats. J Infect Dis 1991; 163: 799-805. 12. MeIJencamp MA, Preheim LC. Pneumococcal pneumonia in a rat model of cirrhosis: effects of cirrhosis on pulmonary defense mechanisms against Streptococcus pneumoniae. J Infect Dis 1991; 163: 102-8.
132
KUMAR
13. Azoulay-Dupuis E, Vallee E, Veber B et aJ. In vivo efficacy of a new fluoroquinolone, sparfloxacin, against penicillin-susceptible and -resistant and multiresistant strains of Streptococcus pneumoniae in a mouse model of pneumonia. Antimicrob Agents Chemother 1992; 36: 2698-703. 14. Abraham E, Stevens P. Effects of granulocyte colony-stimulating factor in modifying mortality from Pseudomonas aeruginosa pneumonia after hemorrhage. CritCare Med 1992; 20: 1127-33. 15. Yang ZP, Kuo CC, Grayston IT. A mouse model of Chlamydia pneumoniae strain TWAR pneumonitis. Infect Immun 1993; 61: 2037-40. 16. van Daal GJ, Eijking EP, So KL et al. Acute respiratory failure during pneumonia induced by Sendai virus. Adv Exp Med Bioi 1992; 316: 319-26. 17. Powles MA, McFadden DC, Pittarelli LA, Schmatz DM. Mouse model for Pneumocystis carinii pneumonia that uses natural transmission to initiate infection. Infect lmmun 1992; 60: 1397-400.
Pathology (1995), 27, April 25. D'Armiento J, Dalal SS, Okada Y et aL Collagenase expression in the lungs of transgenic mice causes pulmonary emphysema. Cell 1992; 71: 955-61. 26. Last lA, Gelzleichter TR, Pinkerton KE et aL.A new model of progressive pulmonary fibrosis in rats. Am Rev Respir Dis 1993; 148: 487-94. 27. Velan GM, Kumar RK, Cohen DD. Pulmonary inflammation and fibrosis following subacute inhalational exposure to silica: determinants of progression. Pathology 1993; 25: 282-90. 28. Li W, Kumar RK, O'Grady R, Vel an GM. Role of Iymphocytes in silicosis: regulation of secretion of macrophage-derived mitogenic activity for fibroblasts. Int J Exp Pathol 1992; 73: 793-800. 29. Hu H, Stein-Streilein J. Hapten-immune pulmonary interstitial fibrosis (HIP IF) in mice requires both CD4 + and CD8 + T Iymphocytes. J Leuk Bioi 1993; 54: 414-22.
18. Boylan Cl, Current WL. Improved rat model of Pneumocystis carinii pneumonia: induced laboratory infections in Pneumocystisfree animals. Infect Immun 1992; 60: 1589-97.
30. Denis M, Cormier Y, Laviolette M, Ghadirian E. T cells in hypersensitivity pneumonitis: effects of in vivo depletion of T cells in a mouse model. Am J Respir Cell Mol BioI 1992; 6: 183-9.
19. Elwood W, Lotvall 10, Barnes Pl, Chung KF. Characterization of allergen-induced bronchial hyperresponsiveness and airway inflammation in actively sensitized Brown-Norway rats. 1 Allergy Clin Immunol 1991; 88: 951-60.
31. Takizawa H, Ohta K, Horiuchi T et al. Hypersensitivity pneumonitis in athymic nude mice: additional evidence of T cell dependency. Am Rev Respir Dis 1992; 146: 479-84.
20. Nagai H, Yamaguchi S, Ingagaki N et al. Effect of anti-IL-S monoclonal antibody on allergic responsiveness in mice. Life Sciences 1993; 53: PL243-7.
32. Gunning WT, Stoner GD, Goldblatt PJ. Glyceraldehyde-3phosphate dehydrogenase and other enzymatic activity in normal mouse lung and in lung tumors. Exp Lung Res 1991; 17: 255-61.
21. Renz H, Saloga 1, Bradley KL et al. Specific V/3 T cell subsets mediate the immediate hypersensitivity response to ragweed allergen. 1 Immunol1993; 151: 1907-17.
33. Belinsky SA, Stefanski SA, Anderson MW. The A/J mouse lung as a model for developing new chemointervention strategies. Cancer Res 1993; 53: 410-6.
22. Kung TT, lones H, Adams GK et al. Characterization of a murine model of allergic pulmonary inflammation. lnt Arch Allergy Appl Immunol 1994; 105: 83-90.
34. Kuo TH, Kubota T, Watanabe M et al. Site-specific chemosensitivity of human small-cell lung carcinoma growing orthotopically compared to subcutaneously in SCID mice: the importance of orthotopic models to obtain relevant drug evaluation data. Anticancer Res 1993; 13: 627-30.
23. Brusselle GG, Kips lC, Tavernier JH et al. Attenuation of allergic airway inflammation in IL-4 deficient mice. Clin Exp Allergy 1994; 24: 73-80. 24. Martorana PA, Brand T, Gardi C et aL The pallid mouse: A model of genetic ai-antitrypsin deficiency. Lab Invest 1993; 68: 233-41.
35. Davis MR, Manning LS, Whitaker D et al. Establishment of a murine model of malignant mesothelioma. Int J Cancer 1992; 52: 881-6.