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. This antibody is specific for human pulmonary SP-A.