Background: Airway inflammation and airway hyperresponsiveness (AHR) are fundamental features of asthma. Migration of inflammatory cells from the circulation into the lungs is dependent on adhesion molecule interactions. The cell surface adhesion molecule L-selectin has been demonstrated to mediate leukocyte rolling on inflamed and noninflamed pulmonary endothelium. However, its role in the development of airway inflammation and AHR in asthma has not been examined.
Objective: We sought to characterize the role of L-selectin in the recruitment of inflammatory cells to the airway-lung and the development of AHR in a murine model of asthma.
Methods: An ovalbumin (OVA)-induced allergic airway disease model of asthma was applied to L-selectin-deficient (LKO) mice and C57BL/6 wild-type (WT) control mice. The development of airway inflammation was assessed by examining leukocyte influx into bronchoalveolar lavage (BAL) fluid and the lung. Total and differential BAL leukocyte counts were determined, and the immunophenotype of BAL lymphocytes was assessed by means of flow cytometry. The development of AHR was assessed by means of whole-body plethysmography.
Results: Airway-lung inflammation was equivalent in LKO and WT mice sensitized-challenged with OVA, as measured by total and differential BAL cell counts and histologic analysis of lung tissue. Numbers of eosinophils, neutrophils, lymphocytes, and monocytes in BAL fluid were equivalent in LKO and WT mice. However, phenotypic analysis of BAL lymphocytes demonstrated significantly reduced CD3(+) populations and increased B220(+) populations in LKO compared with WT mice (P <.05). Remarkably, despite a fulminant inflammatory response in the airway-lung in LKO mice sensitized-challenged with OVA, AHR was completely abrogated.
Conclusion: L-selectin plays a crucial role in the development of AHR but not allergic inflammation in an animal model of asthma. L-selectin represents a potential target for novel asthma therapies specifically aimed at controlling AHR.