Complement activation by cell wall fractions of Micropolyspora faeni

The ability of several cell wall fractions of Micropolyspora faeni, a thermophilic actinomycete associated with farmer's lung disease, to activate complement is reported. Cell walls, obtained by mechanical disruption, were purified by enzyme treatment and chemical extractions. Fractions containing the most purified cell walls were most active in consuming complement, as measured by reduction of hemolytic complement levels of normal human serum. Cell wall fractions activated the alternative complement pathway, as shown by monitoring the conversion of C3 proactivator (factor B) to C3 activator (activated factor B) in the presence of specific cation chelators. Selective degradation of cell walls by lysozyme resulted in a decreased ability to consume complement and implicated peptidoglycan as the major complement-reactive component. The role of this nonspecific complement activation in relation to farmer's lung disease is discussed.