The frequency of precipitins to trichloroacetic acid-extractable antigens from thermophilic actinomycetes in farmer's lung patients and asymptomatic farmers.

The hypothesis that the trichloroacetic acid (TCA)-extractable antigen fractions prepared from Micropolyspora faeni cells and other thermophilic actinomycetes are better diagnostic immunodiffusion reagents for the detection of farmer's lung disease than the crude extracellular antigen concentrates has been tested. The frequency of serum precipitins to the TCA-extractable antigens has been compared in symptomatic farmer's lung patients and in healthy farmers having positive precipitin tests to the crude antigen concentrates of the analogous thermophilic actinomycetes. Sixty-eight per cent of the symptomatic group were found to have precipitins to the M. faeni TCA-extractable antigens compared with only 22 per cent of the asymptomatic group. With regard to the other thermophilic actinomycetes tested, no significant differences in frequencies of precipitins to TCA-extractable antigens between the symptomatic and asymptomatic groups were found. However, the total number of patients available for testing with each of these antigens was small. Sufficient chemical characterization of the TCA-extractable antigens was carried out to show that they were chemically similar to the TCA-extractable antigens prepared by other workers.