Granulocytes and Airway Reactivity1-3 GARY L. LARSEN, ROBERT A. BETHEL, CHARLES G. IRVIN, RICHARD J. MARTIN, and DEREK A. UCHIDA
Pulmonary insults capable of causing airway inflammation often lead to heightened airway reactivity (1).For example, viral respiratory infections (2), exposure to air pollutants such as ozone (3), and antigen inhalation (4) have all been shown to increase airwayreactivity in humans. Thus, the hypothesis has been advanced that inflammation within the airways may alter reactivity. In recent studies, the airwayinflammatory response has been documented through use of bronchoalveolar lavage (BAL) performed before and/or after airway provocation in normal and in asthmatic subjects. Although the number of published reports employing BAL in asthma is relatively small, certain trends have appeared. In clinically stable asthmatics, the total numbers and relative proportions of cells in BAL were very similar to those found in normal nonallergic volunteers, except for a mild increase in eosinophils (5-7) and mast cells (6, 7). In studies of nocturnal asthma, Martin and coworkers (8) found that significant increases in airway reactivity occurred at 4:00 A.M. in asthmatics with nocturnal symptoms. When subjects with nocturnal asthma underwent BAL, significant increases in lavage neutrophils and eosinophils were found at 4 A.M. compared with those found at 4 P.M. On the other hand, asthmatics without nocturnal asthma had significantly smaller increases in airway reactivity and no alteration in their lavage fluid from 4 P.M. to 4 A.M. The antigen-induced late asthmatic response (LAR) in humans also has been associated with a significant increase in eosinophils (9) or both eosinophils and neutrophils (10) within the respiratory tract. In addition, a neutrophilia within lavage fluid was noted after ozone exposure in normal subjects (11). Thus, clinical studies in settings where enhanced airway reactivity is found have documented an increase in inflammatory cells (granulocytes) within the lung as assessed by BAL. In animals, similar stimuli also have been associated with an increase in airway reactivity. For example, dogs develop increases in reactivity after viral infections (12) and exposure to ozone (13). Antigen-induced increases in airwayreactivity also have been seen in sensitized animals after exposure to antigen (14). One advantage of using animal models to study airway inflammation and reactivity is that mechanisms can be addressed more directly. For example, the components of an airway inflammatory response (edema, cellular infiltration) may be correlated with physiologic events. In addition, inflammatory cells may be manipulated in various ways (depletion, repletion, stimulation in vitro), allowing assessment of the potential contribu564
tion of different cell types to changes in lung function. In terms of animal models of "asthma," six species of animals sensitized to an antigen have now been shown to develop antigeninduced airway obstruction both immediately and several hours after challenge (15). In all species, a significant increase in neutrophils and/or eosinophils has been documented by lavage and/or analysis of the pathologic features of the airways during the period of airway obstruction. In addition, in one model (rabbits), an increase in airway reactivity was associated with airway inflammation as defined by neutrophil and eosinophil accumulation within lavage fluid (14). Although the alterations in reactivity in immune rabbits did not correlate with the magnitude of the inflammatory response as defined by lavage, there was a temporal relationship between the two events, and as reactivity returned to preantigen challenge values, so did inflammatory cells in the lavage. Granulocytopenic immune rabbits previously treated with nitrogen mustard failed to develop a late asthmatic response or increase in airway reactivity (16).However, when granulocytopenic immune animals were transfused with homologous white blood cells during antigen challenge, mild airway obstruction again occurred and marked increases in reactivity were noted. Thus, in this model, granulocytes appear to be involved in the process that leads to the airway obstruction and increase in airway reactivity. Other animal models also have addressed the relationship between airway inflammation and alterations in airway function. For example, Chung and coworkers (17) studied the relationship between increases in airway reactivity and pulmonary inflammation in a canine model of ragweed-induced asthma. They found an increase in airway reactivity 6 h after antigen challenge that was associated with increased neutrophil recovery from BAL fluid. Sasaki and coworkers (18)also studied the effects of antigen challenge in Ascarissensitive dogs using metyrapone to block endogenous corticosteroid production. In this study, the magnitude of the late response was significantly correlated with neutrophil accumulation within the lungs as assessed by lavage. A recently described guinea pig model of the late asthmatic response developed by Hutson and coworkers (19) has also begun to address the importance of inflammatory cells in these reactions. In this model, the immediate response was maximal at 2 h and was followed by two late responses that peaked at 17 and 72 h after antigen challenge. Significant increases in BAL neutrophils were noted at 6 and 17 h postchallenge, whereas significant increases in eosinophils were ob-
served at 17and 72 h. Employing this guineapig model, this group recently reported that depletion of neutrophils with antineutrophil sera did not block the pulmonary late-phase response (20). Neutrophil depletion followed by repletion has also been used to study hyperresponsiveness produced by platelet-activating factor (PAF) in canine trachealis (21). Infusion of PAF into arteries of the canine cervical trachea increased responsivenessof the trachealis to vagal stimulation. When this tracheal segment was perfused with autologous blood depleted of leukocytes by centrifugation and dextran sedimentation, reactivity of the muscle did not increase after PAF administration. However, when autologous neutrophils were added back to the blood depleted of leukocytes, an increase in responsiveness was again noted, suggesting a dependency on circulating neutrophils for this PAF-induced alteration in canine airway function. Studies employing both in vitro and in vivo techniques have been performed to better define the effects of neutrophils and eosinophils on airway function. Relatively pure and unactivated populations of these cells were exposed to the same stimulus, opsonized zymosan. When aerosolized into the airwaysof rabbits, products released from highly purified neutrophils did not lead to acute airflow limitation, but they did cause an increase in airway reactivity to histamine (22). On the other hand, supernatants obtained from relatively pure populations of stimulated eosinophils led to acute airway obstruction but no changes in airway reactivity to inhaled histamine (23). Thus, the same stimulus led to elaboration of products that produced different effects on airway function. Although the above observations in humans and animals suggest a relationship between airway inflammation and increases in airway reactivity, increases in reactivity may occur without significant airway inflammation. For example, Evans and coworkers (24) found that an ozone-induced increase in reactivity in rats was not associated with either
1 From the Departments of Pediatrics and Medicine, Pulmonary Physiology Unit, National Jewish Center for Immunology and Respiratory Medicine, University of Colorado School of Medicine, Denver, Colorado. 2 Supported by Grant POI HL-36577 from the National Institutes of Health. 3 Correspondence and requests for reprints should be addressed to Gary L. Larsen, M.D., Associate Professor, Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, 1400Jackson Street, Denver, CO
80206. AM REV RE5PIR DI5 1991; 143:564-565
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a significant increase in neutrophils in the tracheal mucosa or the amount of Evans blue dye extravasated into the trachea in this species. This is in contrast to dogs where increases in reactivity after ozone exposure paralleled the increases in neutrophils in the airway epithelium (13). Cibulas and coworkers (25) also reported that toluene-diisocyanate-induced increases in airway reactivity in the guinea pig can occur in the presence of granulocytopenia, suggesting that alterations in airway function caused by this stimulus are independent of neutrophils and eosinophils in this species of animals. Airway inflammation also can occur without increasing airway reactivity. This was recently demonstrated by Folkerts and colleagues (26) in guinea pigs where endotoxin-induced airway inflammation was associated with bronchial hypo reactivity instead of hyperreactivity. In summary, several observations in humans and in experimental animals have suggested that various inflammatory stimuli may lead to an increase in airway reactivity. Granulocytes (neutrophils and eosinophils) have been associated with alterations of airways function in both humans arid animal models. However, not all stimuli that lead to airway inflammation are associated with an increase in airway reactivity, and increases in airway reactivity may occur without evidence of significant airway inflammation. These observations suggest that multiple mechanisms may lead to increases in airway reactivity, and these mechanisms may be granulocyte-dependent or granulocyte-independent. Furthermore, the type of mechanism(s) leading to alterations in airway reactivity may be both stimulus- and species-specific. References 1. Wilson MC, Irvin CG, Larsen GL. Inflammation and asthma. Semin Respir Med 1987;8:279-86. 2. Empey DW, Laitinen LA, Jacobs L, Gold WM, Nadel JA. Mechanisms of bronchial hyperreactivity in normal subjects after respiratory tract infection. Am Rev Respir Dis 1976; 113:131-9. 3. Holtzman MJ, Cunningham JH, Sheller JR,
IrsiglerGB, Nadel JA, BousheyHA. Effect of ozone on bronchial reactivity in atopic and nonatopic subjects. Am Rev Respir Dis 1979; 120:1059-67. 4. Boulet LP, Cartier A, Thomson NC, Roberts RS, Dolovich J, Hargreave FE. Asthma and increasesin nonallergic bronchial responsivenessfrom seasonal pollen exposure. J Allergy Clin Immunol 1983; 71:399-406. 5. Fick RB, Richerson HB, zavala DC, Hunninghake GW. Bronchoalveolar lavage in allergic asthmatics. Am Rev Respir Dis 1987; 135:1204-9. 6. Wardlaw AJ, Dunnette S, Gleich GJ, Collins JV, Kay AB. Eosinophils and mast cells in bronchoalveolar lavage in subjects with mild asthma. Relationship to bronchial hyperreactivity. Am Rev Respir Dis 1988; 137:62-9. 7. Kirby JG, Hargreave FE, Gleich GJ, O'Byrne PM. Bronchoalveolar cell profiles of asthmatic and nonasthmatic subjects. Am Rev Respir Dis 1987; 136:379-83. 8. Martin RJ, Cicutto LC, Smith HR, Ballard RD, Szefler SJ. Airway inflammation in nocturnal asthma. Am Rev Respir Dis 1991; 143:351-7. 9. de Monchy JGR, Kauffman HF, Venge P, et at. Bronchoalveolar eosinophilia during allergeninduced late asthmatic reactions. Am Rev Respir Dis 1985; 131:373-6. 10. Metzger WJ, Richerson HB, Worden K, Monick M, Hunninghake GW. Bronchoalveolar lavage of allergic asthmatic patients following allergen bronchoprovocation. Chest 1986; 89:477-83. 11. Seltzer J, Bigby BG, Stulbarg M, et at. Or induced change in bronchial reactivity to methacholine and airway inflammation in humans. J Appl Physiol 1986; 60:1321-6. 12. Inoue H, Horio S, Ichinose M, et at. Changes in bronchial reactivity to acetylcholine with type C influenza virus infection in dogs. Am Rev Respir Dis 1986; 133:367-71. 13. Holtzman MJ, Fabbri LM, O'Byrne PM, et at. Importance of airway inflammation for hyperresponsiveness induced by ozone. Am Rev Respir Dis 1983; 127:686-90. 14. Marsh WR, Irvin CG, Murphy KR, Behrens BL, Larsen GL. Increases in airway reactivity to histamine and inflammatory cells in bronchoalveolar lavage after the late asthmatic response in an animal model. Am Rev Respir Dis 1985;131:875-9. 15. Larsen GL. Animal models of the late asthmatic response. In: Kay AB, ed. Balliere's clinical immunology and allergy. The allergic basis of asthma. London: Balliere Tindall, 1988; 91-109. 16. Murphy KR, Wilson MC, Irvin CG, et at. The
requirement for polymorphonuclear leukocytes in the late asthmatic response and heightened airway reactivity in an animal model. Am Rev Respir Dis 1986; 134:62-8. 17. Chung KF, Becker AB, Lazarus SC, Frick 0 L, Nadel JA, Gold WM. Antigen-induced airway hyperresponsiveness and pulmonary inflammation in allergic dogs. J Appl Physiol1985; 58:1347-53. 18. Sasaki H, Yanai M, Shimura S, et at. Late asthmatic response to Ascaris antigen challenge in dogs treated with metyrapone. Am Rev Respir Dis 1987; 136:1459-65. 19. Hutson PA, Church MK, Clay TP, Miller P, Holgate ST.Early- and late-phase bronchoconstriction after allergen challenge of nonanesthetized guinea pigs. I. The association of disordered airway physiology to leukocyte infiltration. Am Rev Respir Dis 1988; 137:548-57. 20. Hutson PA, VarleyIG, Sanjar S, KingsM, Holgate ST, Church MK: Evidence that neutrophils do not participate in the late-phase airway response provoked by ovalbumin inhalation in conscious, sensitized guinea pigs. Am Rev Respir Dis 1990; 141:535-9. 21. Bethel RA, Lien DC, Henson PM, Worthen GS. Effects of neutrophil depletion and repletion on platelet activating factor-induced hyperresponsivenessof canine trachea. Am Rev Respir Dis 1988; 137:98. 22. Irvin CG, Baltopoulos G, Honour J, Seccombe JF, Henson PM. Lipid mediators released by activated human neutrophils which increase airway reactivity (abstract). Am Rev Respir Dis 1986; 133:AI75. 23. Uchida DA, Kimani G, Larsen GL, Irvin CG. Effects on airways function of supernatants from phagocytosing eosinophils (abstract). Am Rev Respir Dis 1987; 135:AI78. 24. Evans TW, Brokaw JJ, ChungKF, Nadel.JA, McDonald DM. Ozone-induced bronchial hyperresponsivenessin the rat is not accompanied by neutrophil influx or increased vascular permeability in the trachea. Am Rev Respir Dis 1988;138:140-4. 25. Cibulas W, Brooks SM, Murlas CG, Miller ML, McKay RT.Toluene diisocyanate-induced airway hyperreactivity in guinea pigs depleted of granulocytes. J Appl Physiol 1988; 64:1773-8. 26. Folkerts G, Henricks PAJ, Slootweg PJ, Nijkamp FP. Endotoxin-induced inflammation and injury of the guinea pig respiratory airways cause bronchial hyporeactivity. Am Rev Respir Dis 1988; 137:1441-8.
Pulmonary insults capable of causing airway inflammation often lead to heightened airway reactivity (1).For example, viral respiratory infections (2), exposure to air pollutants such as ozone (3), and antigen inhalation (4) have all been shown to increase airwayreactivity in humans. Thus, the hypothesis has been advanced that inflammation within the airways may alter reactivity. In recent studies, the airwayinflammatory response has been documented through use of bronchoalveolar lavage (BAL) performed before and/or after airway provocation in normal and in asthmatic subjects. Although the number of published reports employing BAL in asthma is relatively small, certain trends have appeared. In clinically stable asthmatics, the total numbers and relative proportions of cells in BAL were very similar to those found in normal nonallergic volunteers, except for a mild increase in eosinophils (5-7) and mast cells (6, 7). In studies of nocturnal asthma, Martin and coworkers (8) found that significant increases in airway reactivity occurred at 4:00 A.M. in asthmatics with nocturnal symptoms. When subjects with nocturnal asthma underwent BAL, significant increases in lavage neutrophils and eosinophils were found at 4 A.M. compared with those found at 4 P.M. On the other hand, asthmatics without nocturnal asthma had significantly smaller increases in airway reactivity and no alteration in their lavage fluid from 4 P.M. to 4 A.M. The antigen-induced late asthmatic response (LAR) in humans also has been associated with a significant increase in eosinophils (9) or both eosinophils and neutrophils (10) within the respiratory tract. In addition, a neutrophilia within lavage fluid was noted after ozone exposure in normal subjects (11). Thus, clinical studies in settings where enhanced airway reactivity is found have documented an increase in inflammatory cells (granulocytes) within the lung as assessed by BAL. In animals, similar stimuli also have been associated with an increase in airway reactivity. For example, dogs develop increases in reactivity after viral infections (12) and exposure to ozone (13). Antigen-induced increases in airwayreactivity also have been seen in sensitized animals after exposure to antigen (14). One advantage of using animal models to study airway inflammation and reactivity is that mechanisms can be addressed more directly. For example, the components of an airway inflammatory response (edema, cellular infiltration) may be correlated with physiologic events. In addition, inflammatory cells may be manipulated in various ways (depletion, repletion, stimulation in vitro), allowing assessment of the potential contribu564
tion of different cell types to changes in lung function. In terms of animal models of "asthma," six species of animals sensitized to an antigen have now been shown to develop antigeninduced airway obstruction both immediately and several hours after challenge (15). In all species, a significant increase in neutrophils and/or eosinophils has been documented by lavage and/or analysis of the pathologic features of the airways during the period of airway obstruction. In addition, in one model (rabbits), an increase in airway reactivity was associated with airway inflammation as defined by neutrophil and eosinophil accumulation within lavage fluid (14). Although the alterations in reactivity in immune rabbits did not correlate with the magnitude of the inflammatory response as defined by lavage, there was a temporal relationship between the two events, and as reactivity returned to preantigen challenge values, so did inflammatory cells in the lavage. Granulocytopenic immune rabbits previously treated with nitrogen mustard failed to develop a late asthmatic response or increase in airway reactivity (16).However, when granulocytopenic immune animals were transfused with homologous white blood cells during antigen challenge, mild airway obstruction again occurred and marked increases in reactivity were noted. Thus, in this model, granulocytes appear to be involved in the process that leads to the airway obstruction and increase in airway reactivity. Other animal models also have addressed the relationship between airway inflammation and alterations in airway function. For example, Chung and coworkers (17) studied the relationship between increases in airway reactivity and pulmonary inflammation in a canine model of ragweed-induced asthma. They found an increase in airway reactivity 6 h after antigen challenge that was associated with increased neutrophil recovery from BAL fluid. Sasaki and coworkers (18)also studied the effects of antigen challenge in Ascarissensitive dogs using metyrapone to block endogenous corticosteroid production. In this study, the magnitude of the late response was significantly correlated with neutrophil accumulation within the lungs as assessed by lavage. A recently described guinea pig model of the late asthmatic response developed by Hutson and coworkers (19) has also begun to address the importance of inflammatory cells in these reactions. In this model, the immediate response was maximal at 2 h and was followed by two late responses that peaked at 17 and 72 h after antigen challenge. Significant increases in BAL neutrophils were noted at 6 and 17 h postchallenge, whereas significant increases in eosinophils were ob-
served at 17and 72 h. Employing this guineapig model, this group recently reported that depletion of neutrophils with antineutrophil sera did not block the pulmonary late-phase response (20). Neutrophil depletion followed by repletion has also been used to study hyperresponsiveness produced by platelet-activating factor (PAF) in canine trachealis (21). Infusion of PAF into arteries of the canine cervical trachea increased responsivenessof the trachealis to vagal stimulation. When this tracheal segment was perfused with autologous blood depleted of leukocytes by centrifugation and dextran sedimentation, reactivity of the muscle did not increase after PAF administration. However, when autologous neutrophils were added back to the blood depleted of leukocytes, an increase in responsiveness was again noted, suggesting a dependency on circulating neutrophils for this PAF-induced alteration in canine airway function. Studies employing both in vitro and in vivo techniques have been performed to better define the effects of neutrophils and eosinophils on airway function. Relatively pure and unactivated populations of these cells were exposed to the same stimulus, opsonized zymosan. When aerosolized into the airwaysof rabbits, products released from highly purified neutrophils did not lead to acute airflow limitation, but they did cause an increase in airway reactivity to histamine (22). On the other hand, supernatants obtained from relatively pure populations of stimulated eosinophils led to acute airway obstruction but no changes in airway reactivity to inhaled histamine (23). Thus, the same stimulus led to elaboration of products that produced different effects on airway function. Although the above observations in humans and animals suggest a relationship between airway inflammation and increases in airway reactivity, increases in reactivity may occur without significant airway inflammation. For example, Evans and coworkers (24) found that an ozone-induced increase in reactivity in rats was not associated with either
1 From the Departments of Pediatrics and Medicine, Pulmonary Physiology Unit, National Jewish Center for Immunology and Respiratory Medicine, University of Colorado School of Medicine, Denver, Colorado. 2 Supported by Grant POI HL-36577 from the National Institutes of Health. 3 Correspondence and requests for reprints should be addressed to Gary L. Larsen, M.D., Associate Professor, Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, 1400Jackson Street, Denver, CO
80206. AM REV RE5PIR DI5 1991; 143:564-565
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GRANULOCYTES AND AIRWAY REACTIVITY
a significant increase in neutrophils in the tracheal mucosa or the amount of Evans blue dye extravasated into the trachea in this species. This is in contrast to dogs where increases in reactivity after ozone exposure paralleled the increases in neutrophils in the airway epithelium (13). Cibulas and coworkers (25) also reported that toluene-diisocyanate-induced increases in airway reactivity in the guinea pig can occur in the presence of granulocytopenia, suggesting that alterations in airway function caused by this stimulus are independent of neutrophils and eosinophils in this species of animals. Airway inflammation also can occur without increasing airway reactivity. This was recently demonstrated by Folkerts and colleagues (26) in guinea pigs where endotoxin-induced airway inflammation was associated with bronchial hypo reactivity instead of hyperreactivity. In summary, several observations in humans and in experimental animals have suggested that various inflammatory stimuli may lead to an increase in airway reactivity. Granulocytes (neutrophils and eosinophils) have been associated with alterations of airways function in both humans arid animal models. However, not all stimuli that lead to airway inflammation are associated with an increase in airway reactivity, and increases in airway reactivity may occur without evidence of significant airway inflammation. These observations suggest that multiple mechanisms may lead to increases in airway reactivity, and these mechanisms may be granulocyte-dependent or granulocyte-independent. Furthermore, the type of mechanism(s) leading to alterations in airway reactivity may be both stimulus- and species-specific. References 1. Wilson MC, Irvin CG, Larsen GL. Inflammation and asthma. Semin Respir Med 1987;8:279-86. 2. Empey DW, Laitinen LA, Jacobs L, Gold WM, Nadel JA. Mechanisms of bronchial hyperreactivity in normal subjects after respiratory tract infection. Am Rev Respir Dis 1976; 113:131-9. 3. Holtzman MJ, Cunningham JH, Sheller JR,
IrsiglerGB, Nadel JA, BousheyHA. Effect of ozone on bronchial reactivity in atopic and nonatopic subjects. Am Rev Respir Dis 1979; 120:1059-67. 4. Boulet LP, Cartier A, Thomson NC, Roberts RS, Dolovich J, Hargreave FE. Asthma and increasesin nonallergic bronchial responsivenessfrom seasonal pollen exposure. J Allergy Clin Immunol 1983; 71:399-406. 5. Fick RB, Richerson HB, zavala DC, Hunninghake GW. Bronchoalveolar lavage in allergic asthmatics. Am Rev Respir Dis 1987; 135:1204-9. 6. Wardlaw AJ, Dunnette S, Gleich GJ, Collins JV, Kay AB. Eosinophils and mast cells in bronchoalveolar lavage in subjects with mild asthma. Relationship to bronchial hyperreactivity. Am Rev Respir Dis 1988; 137:62-9. 7. Kirby JG, Hargreave FE, Gleich GJ, O'Byrne PM. Bronchoalveolar cell profiles of asthmatic and nonasthmatic subjects. Am Rev Respir Dis 1987; 136:379-83. 8. Martin RJ, Cicutto LC, Smith HR, Ballard RD, Szefler SJ. Airway inflammation in nocturnal asthma. Am Rev Respir Dis 1991; 143:351-7. 9. de Monchy JGR, Kauffman HF, Venge P, et at. Bronchoalveolar eosinophilia during allergeninduced late asthmatic reactions. Am Rev Respir Dis 1985; 131:373-6. 10. Metzger WJ, Richerson HB, Worden K, Monick M, Hunninghake GW. Bronchoalveolar lavage of allergic asthmatic patients following allergen bronchoprovocation. Chest 1986; 89:477-83. 11. Seltzer J, Bigby BG, Stulbarg M, et at. Or induced change in bronchial reactivity to methacholine and airway inflammation in humans. J Appl Physiol 1986; 60:1321-6. 12. Inoue H, Horio S, Ichinose M, et at. Changes in bronchial reactivity to acetylcholine with type C influenza virus infection in dogs. Am Rev Respir Dis 1986; 133:367-71. 13. Holtzman MJ, Fabbri LM, O'Byrne PM, et at. Importance of airway inflammation for hyperresponsiveness induced by ozone. Am Rev Respir Dis 1983; 127:686-90. 14. Marsh WR, Irvin CG, Murphy KR, Behrens BL, Larsen GL. Increases in airway reactivity to histamine and inflammatory cells in bronchoalveolar lavage after the late asthmatic response in an animal model. Am Rev Respir Dis 1985;131:875-9. 15. Larsen GL. Animal models of the late asthmatic response. In: Kay AB, ed. Balliere's clinical immunology and allergy. The allergic basis of asthma. London: Balliere Tindall, 1988; 91-109. 16. Murphy KR, Wilson MC, Irvin CG, et at. The
requirement for polymorphonuclear leukocytes in the late asthmatic response and heightened airway reactivity in an animal model. Am Rev Respir Dis 1986; 134:62-8. 17. Chung KF, Becker AB, Lazarus SC, Frick 0 L, Nadel JA, Gold WM. Antigen-induced airway hyperresponsiveness and pulmonary inflammation in allergic dogs. J Appl Physiol1985; 58:1347-53. 18. Sasaki H, Yanai M, Shimura S, et at. Late asthmatic response to Ascaris antigen challenge in dogs treated with metyrapone. Am Rev Respir Dis 1987; 136:1459-65. 19. Hutson PA, Church MK, Clay TP, Miller P, Holgate ST.Early- and late-phase bronchoconstriction after allergen challenge of nonanesthetized guinea pigs. I. The association of disordered airway physiology to leukocyte infiltration. Am Rev Respir Dis 1988; 137:548-57. 20. Hutson PA, VarleyIG, Sanjar S, KingsM, Holgate ST, Church MK: Evidence that neutrophils do not participate in the late-phase airway response provoked by ovalbumin inhalation in conscious, sensitized guinea pigs. Am Rev Respir Dis 1990; 141:535-9. 21. Bethel RA, Lien DC, Henson PM, Worthen GS. Effects of neutrophil depletion and repletion on platelet activating factor-induced hyperresponsivenessof canine trachea. Am Rev Respir Dis 1988; 137:98. 22. Irvin CG, Baltopoulos G, Honour J, Seccombe JF, Henson PM. Lipid mediators released by activated human neutrophils which increase airway reactivity (abstract). Am Rev Respir Dis 1986; 133:AI75. 23. Uchida DA, Kimani G, Larsen GL, Irvin CG. Effects on airways function of supernatants from phagocytosing eosinophils (abstract). Am Rev Respir Dis 1987; 135:AI78. 24. Evans TW, Brokaw JJ, ChungKF, Nadel.JA, McDonald DM. Ozone-induced bronchial hyperresponsivenessin the rat is not accompanied by neutrophil influx or increased vascular permeability in the trachea. Am Rev Respir Dis 1988;138:140-4. 25. Cibulas W, Brooks SM, Murlas CG, Miller ML, McKay RT.Toluene diisocyanate-induced airway hyperreactivity in guinea pigs depleted of granulocytes. J Appl Physiol 1988; 64:1773-8. 26. Folkerts G, Henricks PAJ, Slootweg PJ, Nijkamp FP. Endotoxin-induced inflammation and injury of the guinea pig respiratory airways cause bronchial hyporeactivity. Am Rev Respir Dis 1988; 137:1441-8.
