Isolation and characterization of proteins associated with the lung surfactant system.

Rabbit lung washings and purified lung surfactant were delipidated without precipitation or loss of protein. This enabled effective study of the proteins by electrophoretic and immunoelectrophoretic techniques. The lung washings contained secretory immunoglobulin A and several serum proteins. The protein composition of purified lung surfactant was the same as the unfractionated lung washings confirming our previous study which indicated that there is no specific protein associated with surfactant phospholipids obtained by alveolar lavage with isotonic saline.