Pulmonary surfactant-associated protein B (SP-B)

Pulmonary surfactant-associated protein B (SP-B) is a small, highly hydrophobic protein essential for the biophysical function of the lung surfactant film (UniProt P07483). It is synthesized by alveolar type II cells and works in conjunction with phospholipids to reduce surface tension at the air-liquid interface of the alveoli, preventing their collapse during expiration (StatPearls, Physiology, Pulmonary Surfactant). SP-B is uniquely critical for life; its absence, due to genetic mutations in the SFTPB gene or prematurity, results in lethal respiratory failure (PubMed, PMID: 8107770). In clinical practice, SP-B is a key component of exogenous surfactant preparations, such as Poractant alfa and Beractant, used to treat neonatal respiratory distress syndrome (FDA Label, Curosurf). These drugs aim to mimic the natural surfactant film to improve lung compliance and gas exchange in patients with surfactant deficiency or dysfunction (NIH, Surfactant Replacement Therapy). Beyond its mechanical role, SP-B also contributes to the structural organization of tubular myelin and may play a minor role in the pulmonary innate immune response.

Other names

SFTPBSurfactant protein BPulmonary surfactant-associated proteolipid SPL(Phe)18 kDa pulmonary-surfactant-associated proteinPSP-BSurfactant film

Exogenous surfactant replacement therapy restores the biophysical properties of the alveolar lining by providing essential lipids and proteins, specifically SP-B or its mimics, to lower surface tension and prevent alveolar collapse (StatPearls).