Surfactant protein A (SP-A) is synthesized and secreted by lung epithelial cells. It belongs to group III of the family of C-type lectins and members of this group has overall structure consisting of multiple globular 'head' regions linked by triple-helical, collagen-like, strands. This group also includes SP-D and the serum proteins mannan-binding protein, conglutinin and collectin-43, all of which have been shown to bind to the C1q receptor found on a wide variety of cells. Both SP-D and SP-A have been shown to enhance o, Xenopus/Amphibian,ygen radical production by alveolar macrophages. The serum concentration is 45 ng/ml in healthy individuals. SP-A, in the presence of calcium ions, binds to surfactant phospholipids and contributes to lower the surface tension at the air-liquid interface in the alveoli of the mammalian lung and is essential for normal respiration. Genetic variations in SP-A are a cause of susceptibility to pulmonary fibrosis idiopathic (IPF). Pulmonary fibrosis is a lung disease characterized by shortness of breath, radiographically evident diffuse pulmonary infiltrates, and varying degrees of inflammation and fibrosis on biopsy. IPF results in acute lung injury with subsequent scarring and endstage lung disease.