Proteomic analysis of human bronchoalveolar lavage fluid: expression profiling of surfactant‐associated protein A isomers derived from human pulmonary alveolar proteinosis using immunoaffinity detection

Human bronchoalveolar lavage fluid (BALF) proteins from pulmonary alveolar proteinosis (PAP) obtained by washing the epithelial lining of the lung with phosphate-buffered saline, were separated using high resolution two-dimensional gel electrophoresis (2-DE) under denaturing and reducing conditions. By Western blotting, the proteins were transferred from polyacrylamide gel onto a chemical resilient membrane. The surfactant-associated protein A (SP-A) isomers were then identified with enhanced chemiluminescence detection (ECL) using antibody-antigen reaction. Some of the gels were treated with silver staining after 2-DE. The molecular masses of SP-A isomers in BALF from PAP ranged from 20.5 to 26, 26 to 32, and 32 to 42 kDa, respectively; and isoelectric points (pI) were in pH range of 4.5-5.4 under denaturing and reducing conditions. In the mass range of 20.5-26 kDa and pI of 4.5-5.4, there were five isomers, and in mass range of 26-32 kDa and pI of 4.5 to 5.4, there were at least eight isomers on the ECL detection film. However, in the mass range of 32-42 kDa and pI of 4.5-5.4, there were three isomers separated one from another but there was also a cluster of overlapping spots on the ECL detection film. Thus, this communication describes a characteristic 2-DE pattern of SP-A isomers in BALF from PAP as follows. (1) The five isomers of mass 20.5-26 kDa and pI of 4.5-5.4; (2) the eight isomers of mass 26-32 kDa and pI of 4.5-5.4; and (3) the three isomers of mass 32-42 kDa and pI of 4.5-5.4.