The comparative biology of pulmonary surfactant: past, present and future

Richard E. Pattle contributed enormously to the biology of the pulmonary surfactant system. However, Pattle can also be regarded as the founding father of comparative and evolutionary research of the surfactant system. He contributed eight seminal papers of the 167 publications we have located on this topic. In particular, Pattle produced a synthesis interpreting the evolution of the surfactant system that formed the foundation for the area. Prepared 25 years ago this synthesis spawned the three great discoveries in the comparative biology of the surfactant system: (1) that the surfactant system has been highly conserved throughout the enormous radiation of the air breathing vertebrates; (2) that temperature is the major selective condition that influences surfactant composition; (3) that acting as an anti-adhesive is one primitive and ubiquitous function of vertebrate surfactant. Here we review the literature and history of the comparative and evolutionary biology of the surfactant system and highlight the areas of comparative physiology that will contribute to our understanding of the surfactant system in the future. In our view the surfactant system is a neatly packaged system, located in a single cell and highly conserved, yet spectacularly complex. The surfactant system is one of the best systems we know to examine evolutionary processes in physiology as well as gain important insights into gas transfer by complex organisms.