Abstract
Culture filtrate antigens of Micropolyspora faeni grown in a synthetic medium in a stirred fermentor were characterized. The culture filtrate antigens were fractionated by preparative isoelectric focusing with a pH gradient of 3.5 to 5.5. The fractions were pooled according to their reaction with rabbit anti-M. faeni sera. A pool containing two major antigens which were resolved by analytical isoelectric focusing and polyacrylamide disc gel electrophoresis was obtained. One antigen was stainable with Coomassie blue and periodic acid-Schiff stain and was determined to have a mass of 51,000 daltons. The other antigen was stainable only with Coomassie blue and was determined to have a mass of 29,000 daltons. When used at 1 mg/ml, this pool reacted with the sera from all patients with farmer's lung disease by immunodiffusion but failed to react with control sera.