Joanna Floros

Localization of Pulmonary Surfactant Proteins Using Immunohistochemistry and Tissue in Situ Hybridization

Surfactant, a complex mixture of lipids and proteins, is produced by the type II alveolar epithelial cells. Numerous studies have localized surfactant protein A (SP-A) to type II cells of the lung, and recent studies have shown that the type II cells in the human lung are also the site of synthesis of SP-B, one of the hydrophobic surfactant proteins. There have been conflicting reports about additional sites of SP-A production. We have studied the localization of the mRNAs for SP-A, SP-B, and SP-C in the rat and for SP-C in the human lung by tissue in situ hybridization using cRNA probes. The mRNAs for all three rat surfactant proteins and for human SP-C were found in type II alveolar epithelial cells. In addition, the mRNAs for rat SP-A and SP-B were found in nonciliated bronchiolar cells. SP-C mRNA was not detectable in the bronchiolar cells of both rat and human lung tissue. Immunohistochemical studies in the rat lung with antisera to SP-A and SP-B confirmed the presence of the protein in cell types where the mRNA was found, as well as in some alveolar macrophages. Alveolar macrophages in both rat and human lung tissue were negative for all mRNAs. Further studies are required to ascertain whether there are differences in the processing, function, and regulation of these proteins in the different cell types that produce them.

The 35 kd pulmonary surfactant-associated protein is encoded on chromosome 10

SummaryThe genomic components identified by each of two closely related cDNA clones for the major 35 kilodalton non-serum surfactant-associated proteins (PSP-A) were shown to derive from human chromosome 10 by Southern blot analysis of DNAs from human-rodent somatic cell hybrids. By in situ hybridization to human metaphase chromosomes, the cDNA probes were localized to the region 10q21-q24.