Free secretory component and other proteins in human lung lavage.

Subsegmental bronchoalveolar lavage of the lingula and right middle lobe was performed in a group of normal subjects (32 cigarette smokers and 24 non-smokers) to analyze the recoverable fluid for its content of respiratory cells, several proteins including IgG and IgA, and free secretory component, a glycoprotein elaborated by serous bronchial epithelial cells. The lavage fluid obtained from the smokers consistently demonstrated an increased cell yield, reflecting primarily an increase in alveolar macrophages. In addition, the number of polymorphonuclear granulocytes was tenfold greater in smokers, and the total number of lymphocytes recovered was approximately twice that of nonsmokers. As in previous studies, the analysis of proteins contained in bronchoalveolar lavage (BAL) revealed an increase in the ratio of IgA to albumin in both smokers and nonsmokers, as compared with serum; but an increase in the IgG/albumin ratio in BAL was found only in smokers. The total amount of secretory component recovered ...