Activation of the complement sequence by extracts of bacteria and fungi associated with hypersensitivity pneumonitis.

Complement (C) consumption by antigens associated with hypersensitivity pneumonitis was investigated. Micropolyspora faeni in the presence of precipitating antibodies consumed C in a manner similar to the BSA-anti BSA system. An extract of M. faeni was shown to consume C and convert C3PA to C3A in the absence of detectable antibodies. In addition, three species of Aspergillus and two strains of Thermoactinomyces vulgaris were also shown to have the same activity with respect to C3PA. Mucor racemosus, Hormodendrum sp. and a mixed extract of Penicillium did not convert C3PA.