Surfactant and its role in chronic sinusitis.

Although numerous studies have focused on the nature and defensive role of surfactant in the lower airways, relatively little is known about its role in the upper airways. Decreased levels of the main component of surfactant--phospholipids--have been implicated in atrophic rhinitis. The lamellar body arrangement of phospholipids has now been demonstrated in both normal and diseased sinus tissue, resulting in the implication that these structures may play a crucial role in mucociliary clearance against inhaled pathogens, as well as in the regulation of mucous viscosity. Furthermore, they may be secreted from sinonasal ciliated epithelium. Surfactant proteins (SPs) make up a relatively smaller proportion of surfactant, but appear to have an important role in innate immunity. Altered levels of SPs have been observed in a number of respiratory tract diseases. These SPs may prove to play a significant role in chronic sinusitis. Demonstrated expression of SP-A and SP-D in diseased and normal sinus tissue may mean that these SPs are excreted into the airway-lining fluid of the sinuses. Additionally, initial contact and interaction between pathogens and SP-A and SP-D may occur relatively early after inhalation and deposition into the mucus of the respiratory tract. These findings may lead to potential therapeutic options for difficult-to-treat sinus disease in the future.