The presence of surface-active material in the lung alveolus has been known for several decades as being essential for normal lung function. Surfactant is essential for reducing the surface tension at the alveolar air-liquid interface. Pulmonary surfactant is composed of 90% lipids and 10% proteins. There are four non-serum proteins surfactant protein-A (SP-A), surfactant protein-B (SP-B), surfactant protein-C (SP-C) and surfactant protein-D (SP-D) named in chronologic, order of discovery. Lung SPA and SP-D belong to a family of collagen-containing C-type lectin family called collectins. The host defence and controlling inflammatory processes of the lung are the major functions of SP-A and SP-D.