Fig. 1.

Roles of pulmonary surfactants in maintenance of normal lung function. In asthmatic patients, environmental or genetic factors cause deficiency of surfactants, which are important for host defense and immunomodulation. In the absence of surfactants, inhaled exposures such as allergens, pollutants, and microorganisms enhance epithelium damage or cytokine production, leading to airway inflammation/remodeling associated with lung dysfunction. SP, surfactant protein