Production of FBG by lung epithelial cells stimulated with pro-inflammatory mediators. Immunoprecipitation of secreted (media) and intracellular (cells) FBG was performed using purified rabbit antihuman FBG IgG coupled to Protein A-Sepharose. (A) A fluorograph of immunoprecipitated proteins electrophoresed on a 5% to 15% polyacrylamide gel after reduction and denaturation. Untreated HepG2 cells served as the positive control cell line for FBG biosynthesis. In lane 1, untreated HepG2 cells; lane 2, untreated A549 cells; lane 3, DEX-treated A549 cells; lane 4, IL-6–treated A549 cells; lane 5, DEX + IL-6–treated A549 cells. The position of migration of the FBG Aα, Bβ, and γ chain polypeptides is denoted. Fibronectin (FN) bound nonspecifically to anti-FBG IgG-Protein A-Sepharose. (B) A 2% agarose gel electrophoresis of nonreduced FBG immunoprecipitated from media of metabolically labeled A549 cells treated as described for (A), lanes 2-5; lane 1, nonreduced FBG immunoprecipitated from untreated, metabolically labeled HepG2 cell conditioned media. Molecular weight markers are denoted in the left margin.