IgA antibody against Aspergillus fumigatus antigen in patients with allergic bronchopulmonary aspergillosis.

IgA antibodies against Aspergillus fumigatus (Af) antigen were measured by a radioimmunoassay in sera from patients with allergic bronchopulmonary aspergillosis (ABPA) and compared with IgA antibody levels in asthmatics who had positive prick tests to Af and normal controls. The assay for IgA antibody discriminated between both control groups and the ABPA group at two serum dilutions (10(-2) and 10(-3)) but did not discriminate all individual ABPA sera from the peak levels of antibody in the control groups. IgA antibody against Af may participate in the immunopathogenetics of pulmonary inflammation in some cases of ABPA and may be of some diagnostic value in some, but not all, cases.