POTENTIAL ROLE OF SURFACTANT PROTEIN-A AND PROTEIN-D IN INNATE LUNG DEFENSE AGAINST PATHOGENS

The physiological role of pulmonary surfactant is probably not limited to conferring mechanical stability to the alveoli. Increasing evidenc e suggests that surfactant components, in particular the hydrophilic s urfactant proteins SP-A and SP-D, play potentially important roles in host defense mechanisms. Both SP-A and SP-D are collagenous C-type lec tins (collectins) that are structurally and, perhaps, functionally rel ated to collectins in the circulation. As will be discussed in this re view, evidence is accumulating that the alveolar collectins SP-A and S P-D could be important components of a first-line defense system again st infiltrating pathogenic micro-organisms and viruses.