Fas deficiency delays the resolution of airway hyperresponsiveness after allergen sensitization and challenge

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Background: In asthma, persistent inflammation might be the result of (1) an impaired ability to clear inflammatory cells from the airways and/or (2) impaired apoptotic responses. Objective: In a mouse model, we investigated the regulatory role of Fas (CD95)–induced apoptosis in the development and resolution of airway inflammation and airway hyperresponsiveness (AHR). Methods: Mice that were either Fas-sufficient (wild-type; WT) or Fas-deficient (lpr ) were sensitized by intraperitoneal injections of ovalbumin (OVA) and challenged once intranasally with OVA (IP-IN mice). Control (IN) mice were challenged only. Results: IP-IN WT mice developed AHR at 48 hours; changes in airway resistance resolved by 96 hours. Airway responsiveness at 48 hours in IP-IN lpr mice was similar to that in IP-IN WT mice. However, in contrast to WT mice, IP-IN lpr mice sustained significant AHR at 96 hours in comparison with IN lpr mice; the AHR resolved by 6 days. Bronchoalveolar lavage fluid cell composition was similar in all of the different groups at 48 hours and 96 hours. Both IP-IN WT mice and lpr mice exhibited similar tissue eosinophilia, whereas IP-IN lpr mice had significantly lower numbers of TdT-mediated dUTP nick end labeling (TUNEL)–positive cells in comparison with IP-IN WT mice at 48 hours. Anti–IL-5 antibody given to IP-IN lpr mice 48 hours and 72 hours after the challenge significantly decreased AHR and eosinophilic inflammation and increased TUNEL-positive cell numbers at 96 hours. Conclusion: These results suggest that Fas expression can regulate the onset and resolution of AHR through an increase in eosinophil apoptosis. (J Allergy Clin Immunol 2001;108:547-56.)