Lung surfactant proteins A and D in innate immune defense.

The lung surfactant proteins (SP) A and D are large multimeric proteins and belong to a family of collagenous C-type lectins designated collectins. Both SP-A and SP-D are believed to play a role in the innate immunity of the lung. SP-A and SP-D bind to a broad spectrum of pathogens, including bacteria, viruses, fungi and yeasts but also lipopolysaccharides and allergens. Furthermore, SP-A and SP-D enhance the clearing of various pathogens by neutrophils and macrophages in vitro. Recent in vivo studies on SP-A deficient mice also support a role of SP-A in host defense.