Immunologic studies in hypersensitivity pneumonitis--quantitative precipitins and complement-fixing antibodies in symptomatic and asymptomatic pigeon breeders.

Quantitative precipitation and complement fixation tests were performed on sera from a group of patients with hypersensitivity pneumonitis (pigeon breeders' disease). Their antibody levels were compared to a selected group of similarly exposed but asymptomatic subjects. The quantity of precipitating antibodies was generally greater in serum from symptomatic breeders, although quantities in the serum from some of the asymptomatic subjects were greater than that seen in ill breeders. Complement-fixing antibodies were detected in the serum of both groups. Here again, complement-fixing activity was generally greater in the serum of ill breeders. However, one asymptomatic breeder showed complement-fixing activity greater than most of the symptomatic breeder group. These findings indicate that the presence of complement-fixing antibodies per se in serum to pigeon gamma-globulin is not sufficient to cause the symptoms of pigeon breeders' disease. We suggest that other factor(s) may be involved, such as lgE- or cell-mediated hypersensitivity.