One function of the pulmonary collectins, surfactant proteins A1, A2, A3 and D (SFTPAs, D), is that they influence surfactant homeostasis, contributing to the physical structures of lipids in the alveoli and to the regulation of surfactant function and metabolism. They are directly secreted from alveolar type II cells into the airway to function as part of the surfactant. The mechanism of secretion is unknown. Mutations in SFTPA2 disrupt protein structure and the defective protein is retained in the ER membrane causing idiopathic pulmonary fibrosis (IPF; MIM:178500). IPF is one of a family of idiopathic pneumonias sharing clinical features of shortness of breath, formation of scar tissue and varying degrees of inflammation and/or fibrosis on lung biopsy. IPF is typically progressive, leading to death from respiratory failure within 2-5 years of diagnosis in the majority of instances (Meltzer & Noble 2008, Noble & Barkauskas 2012).