Abstract

Immunodiffusion, immunoosmophoresis, and precipitin inhibition tests were carried out on various categories of sera with extracts of Micropolyspora faeni (Thermopolyspora polyspora), Aspergillus fumigatus, and Thermoactinomyces vulgaris. The sera were from clinical cases of farmer's lung, from symptomless farm workers, from expectant mothers, from tuberculous and from asthmatic patients, and from patients with miscellaneous lung disorders. The clinical cases of farmer's lung became divisible into two groups by serological tests for antibody to a particular soluble antigenic component of M. faeni. The suggestion is made that one of these two groups of cases may be aetiologically unrelated to M. faeni. One of six sera tested in this group reacted strongly with an extract of T. vulgaris. Antibodies to certain components of some extracts of M. faeni and of A. fumigatus were found in a high proportion of normal sera. Possible reasons for this finding have been given.