Surfactant protein A: Regulation of innate and adaptive immune responses in lung inflammation

Although the bulk of available studies demonstrate a role for SP-A and SP-D in pulmonary innate immunity, a growing body of literature supports the possibility that the lung collectins directly mediate functions of cells of the adaptive immune response. The report by Yang and coworkers (1) lends credence to the hypothesis that SP-A and SP-D may mediate cross-talk between innate and adaptive immunity in the lungs, a prospect that requires further investigation. The current study also raises the provocative possibility that SP-A containing surfactant preparations may be important for treatment of idiopathic pneumonitits syndrome and other pulmonary inflammatory diseases. Currently, neither SP-A nor SP-D are components of the surfactant replacement therapies that are routinely used to treat infant respiratory distress syndrome or in the surfactant preparations that have been tested as therapies for acute respiratory distress syndrome, an inflammatory disease associated with deficiencies in SP-A and SP-D (60) as well as other surfactant components (61-63). Although there are still many unanswered questions about the functions of these proteins, the rationale is building for considering these proteins as therapies for lung inflammation.