SP-D: Proteins and Enzymes

Surfactant Protein D (SP-D) is a collectin family protein consisting of a collagen-like sequence followed by a C-type lectin domain. It is synthesized primarily in the lung by alveolar type II cells and unciliated bronchial epithelial cells. In addition, SP-D is produced by epithelial cells of the gastrointestinal tract and exocrine glands. SP-D binds to patterns of neutral sugars on micro-organisms to mediate direct opsonization and phagocytosis and is an important component of the innate immune system.