Rheumatoid factor activity in serum and bronchoalveolar lavage fluid from patients with acute hypersensitivity pneumonitis.

The presence of rheumatoid factor was detected in both serum and bronchoalveolar lavage fluid (BALF) from patients with acute pigeon breeder's disease. IgM rheumatoid factor was positive in 14 of 20 serum samples and 6 of 20 BALF samples by ELISA. In contrast, negative results were found in 20 healthy subjects with a history of avian antigen exposure, as well as in the serum and BALF from 10 normal subjects. The simultaneous presence of rheumatoid factor in serum and BALF occurred in five patients, and four of them revealed high levels of rheumatoid factor in BALF in comparison with serum determinations. These abnormalities may play an important role during the acute inflammatory reaction in hypersensitivity pneumonitis.