SP-B is expressed in pulmonary adenocarcinomas with acinar, papillary, bronchioloalveolar, and solid growth patterns. Squamous cell and large cell carcinomas of the lung and nonpulmonary adenocarcinomas do not express SP-B. Pulmonary surfactant-associated protein B' is a membrane protein which manufactures surfactant.Humans and animals born with a congenital absence of SP-B suffer from intractable respiratory failure.

The SFTPB is an amphipathic surfactant protein essential for lung function and homeostasis after birth. Pulmonary surfactant is a lipid-rich material that prevents lung collapse by lowering surface tension at the air-liquid interface in the alveoli of lung. SPB enhances the rate of spreading and increases the stability of surfactant monolayers in vitro.