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Studies of tracheal secretion using serous cell cultures and monoclonal antibodies.

The glycoconjugate composition of tracheal secretions varies with physiological and pathophysiological parameters. Believing that these differences might be explained by metabolic or regulatory modifications of particular cell types, we have developed strategies for biochemical analysis at the cellular level. We have produced monoclonal antibodies whose determinants are restricted to a single secretory cell type (serous, mucous, or goblet cell granules, or ciliated cell glycocalyx). By enzyme immunoassay (ELISA), we have characterized four of the antibodies biochemically, and have also used the antibodies as quantitative molecular probes to detect release of antigen from mixed cell explants. Four of the antigens are carried by carbohydrate moieties of high molecular weight glycoproteins. Western blot analysis shows their molecular weight in reducing gels (SDS-PAGE) to exceed 200 kD. When used in parallel with pulse-chase labeling studies, the antibodies are both more sensitive and specific (than bound radioactivity) in detecting gland or goblet cell secretion in response to autonomic drugs or proteases. We have also isolated and cultured serous gland cells for physiological and biochemical studies. These cells express serous cell phenotype as reflected by ultrastructure, histochemistry, and lysozyme activity. Biochemical analysis of their secretory products reveals glycoconjugate components which are heterogeneous with respect to both molecular weight and charge. Radiolabeled secretory products eluting in the void volume of Sepharose C1 4B were completely degraded by chondroitinase ABC. This indicates that the major glycoconjugate produced by serous cell is a proteoglycan resembling chondroitin sulfate.