Different classes of antibody activities to Trichosporon cutaneum antigen in summer-type hypersensitivity pneumonitis by enzyme-linked immunosorbent assay.

To assess the diagnostic value of antibody activities to Trichosporon cutaneum antigen in patients with summer-type hypersensitivity pneumonitis in Japan, we measured the serum IgG, IgA, and IgM antibodies to saline-soluble antigen of homogenized T. cutaneum cells by enzyme-linked immunosorbent assay (ELISA). The IgG antibody activity was observed in serum samples from 25 (83%) of the 30 patients and in 9 (82%) of the 11 asymptomatic family members. The IgA antibody activity was found in 25 (83%) of the patients but in only 3 (27%) of asymptomatic family members. Unexpectedly, we found no significant correlation between the IgG and IgA antibody activities to the same antigen in individual patients. Moreover, although the IgG antibody activity was related to the precipitating antibody, the IgA antibody activity was not. The IgM antibody activity by ELISA was found in only 5 (17%) of the patients. The IgG+IgA+IgM antibody activity was demonstrated in 27 (90%) of the 30 patients, and of 3 serum samples that were found negative by the ELISA method, 2 were positive by the IFA method. We conclude that the detection of the serum IgG and IgA antibody activities to T. cutaneum antigen by ELISA is a simple and useful serodiagnostic test for summer-type hypersensitivity pneumonitis. Measurement of the IgA antibody activity is especially helpful in discriminating symptomatic from asymptomatic family members.