Complement-binding antibodies to Aspergillus fumigatus in patients with pulmonary aspergillosis

Complement-binding antibodies against Aspergillus fumigatus were determined by a fluorescent antibody technique with purified human Clq as the source of complement. Clq binding aspergillus antibodies were found in 8 (67%) of 12 patients with pulmonary aspergillosis, in 4 (57%) of 7 patients with suspected pulmonary aspergillosis, in one (14%) of 7 patients with precipitating antibodies to A. fumigatus of undetermined clinical significance, and in 4 (7%) of 54 healthy blood donors. Sera from patients with definite or probable aspergillosis produced an immunofluorescent staining of hyphal cytoplasm, whereas the staining obtained with positive donor sera was confined to hyphal walls. A positive correlation was found between the frequency and titres of Clq binding antibodies and titres of IgG and IgM aspergillus antibodies. Clq binding antibodies were found only in sera with an IgG aspergillus antibody titre greater than or equal to 640. The frequency of Clq binding antibodies in sera with IgG titres greater than or equal to 640 was significantly higher in patients with aspergillosis (67%) than in blood donors (16%) (p = 0.0036). The Clq binding antibody test may provide diagnostic information as well as clues to the pathogenesis of aspergillus lung disease.