ABSTRACT
Mouldy hay was produced in the laboratory by sterilising good hay, inoculating with aqueous suspensions of microorganisms, and incubating at 40 degrees or 60 degrees C. Extracts were tested for presence of farmer's lung hay (F.L.H.) antigen by agar-gel double-diffusion and immunoelectrophoresis tests against sixteen to twenty sera from patients with farmer's lung. F.L.H. antigen developed in hay after: (1) inoculating with mixed microbial suspensions from antigenically active hay; (2) inoculation with mixed suspensions of pure cultures of thermophilic actinomycetes, after raising the pH of the hay to 70 either by prior inoculation with fungi or by infiltration with ammonia vapour; and (3) inoculation at pH 70 with pure cultures of Thermopolyspora polyspora or with Micromonospora vulgaris. F.L.H. antigen did not develop in hay after inoculation with fungi only, or with six other actinomycetes tested, or after prior heating (though some sera reacted to fungal antigens in all these extracts). T. polyspora is the richest source yet found of F.L.H. antigen, and inhalation of an extract by affected subjects produces some of the features of farmer's lung. Pure cultures can produce F.L.H. antigen on artificial media without hay. Spores and mycelium are rich in F.L.H. antigen, and inhalation of the spores may play a part in farmer's lung disease. Other antigens relevant to farmer's lung may be found in other actinomycetes, not yet cultured.