Specific bronchoalveolar lavage IgA antibody in patients with summer-type hypersensitivity pneumonitis induced by Trichosporon cutaneum.

Patients with summer-type hypersensitivity pneumonitis induced by Trichosporon cutaneum were studied with respect to specific IgG, IgA, and secretory IgA (S-IgA) antibody activities to T. cutaneum in serum and bronchoalveolar lavage fluid (BALF). A strain of T. cutaneum was isolated from 1 patient's pillow. All serum samples from the family members (2 patients and 2 asymptomatic) contained IgG antibody activity to T. cutaneum, and the titers showed no difference between the patients and asymptomatic family members. On the other hand, IgA and S-IgA antibody activities in serum and BALF were markedly increased only in the patients, and the titers were well correlated with the clinical course. The BALF/serum ratio of specific antibody activity was markedly elevated in IgA and S-IgA antibody activities in striking contrast to that in IgG, suggesting an immune reaction of the respiratory tract. The bronchial challenge test with T. cutaneum antigen was positive in the patients, but not in an asymptomatic family member. These results indicate that measurement of IgA and S-IgA antibody activities in serum and BALF is useful for diagnosis and evaluation of disease activity in summer-type hypersensitivity pneumonitis.