Surfactant protein B (SP-B) is a small protein that plays a crucial role in the lungs. It is part of the pulmonary surfactant, a substance that reduces surface tension in the alveoli, the tiny air sacs where gas exchange occurs. By helping to keep the alveoli open, SP-B ensures that the lungs can function efficiently during breathing. SP-B is produced by type II alveolar cells and is essential for normal lung function. Deficiencies or mutations in the gene responsible for SP-B can lead to serious respiratory issues, particularly in newborns. Understanding SP-B is important for developing treatments for lung diseases and conditions like neonatal respiratory distress syndrome.