Surfactant protein A (SP-A) is a biomolecule that belongs to the collectin family of proteins and is primarily involved in the immune defense mechanism of the lungs. It is a key component of pulmonary surfactant, a complex mixture of lipids and proteins that lines the alveoli (air sacs) in the lungs. SP-A is produced by type II alveolar cells and is secreted into the fluid lining the alveoli.
Functionally, SP-A acts as an innate immune molecule by recognizing and binding to various pathogens such as bacteria, viruses, fungi, and allergens present in the respiratory tract. This interaction helps to facilitate their clearance and neutralization, preventing their colonization and subsequent infection in the lungs.
Furthermore, SP-A plays a crucial role in regulating the surface tension of the alveoli, ensuring efficient gas exchange during respiration. It does this by reducing the cohesive forces between the alveolar cells, lowering surface tension and preventing alveolar collapse at the end of expiration.
The structure of SP-A consists of a collagen-like domain with globular regions at the ends. These globular regions are responsible for the protein's ability to bind to a wide range of pathogens and participate in immune response activation.
Research has suggested that abnormalities or deficiencies in SP-A expression or function may contribute to various lung diseases, such as respiratory distress syndrome, pneumonia, and chronic obstructive pulmonary disease (COPD). Understanding the role of surfactant protein A in lung health and disease is of significant interest for developing potential therapies and interventions.
