Detection of class-specific antibodies against Micropolyspora faeni antigens in farmers' lung.

Micropolyspora faeni antigens were used for specific IgA, IgG and IgM determination with an ELISA technique, and for specific IgE antibodies by means of RAST in eighteen patients with farmer's lung, in nineteen farmers with other chest conditions, and in twenty-nine controls. The farmers' lung group had significantly higher IgG antibody levels than the controls, while specific IgA levels were elevated in ten cases. Specific IgE and--except for three cases--IgM levels did not differ from the controls. In the group of farmers with other lung diseases, only three had increased levels of specific IgG antibody. The correlation (0.89) between IgG by ELISA and a complement-fixation test indicated that C activation by M. faeni antigens is mediated by IgG antibodies.