[Farmer's lung: IgG-subclass reactivities against thermophilic actinomycetes].

IgG subclass reactivities of patients suffering from farmer's lung, healthy family members and blood donors were tested for specific binding to Micropolyspora faeni extract by means of immunoblot techniques (IEF-Print, Western Blot). In patients' sera IgG1 and IgG2 had shown the strongest reactivities while IgG3- and IgG4-reactivities were not found in all cases. Strong IgG2-reactivities against acidic proteins (pl 3-5) of M. faeni seem to distinguish between patients and exposed or not exposed controls, respectively.