Most monoclonal antibodies (mAbs) to fungi are often found to cross-react with related and non-related fungi. In this study we attempted to shift the immune response towards species-specific antibodies by immunizing mice with preformed immune complexes rather than spores alone.

Balb/c mice were repeatedly immunized with immune complexes composed of the particulate fraction of homogenized spores of P. brevicompactum and mAbs which were previously produced against spores of Penicillium chrysogenum and shown to be highly cross-reactive with P. brevicompactum. The specificities of the resulting mAbs were determined by ELISA against spores of 51 fungal species commonly found in indoor environments.

None of the 12 mAbs produced was found to be speciesspecific for P. brevicompactum and based on their cross-reactivity profiles the 12 mAbs could be allocated to one of 5 different groups. Although immune complex immunization when compared to conventional immunizations with spores alone resulted in a decrease of mAb reactivity to related species of Penicillium and Aspergillus, the reactivity of mAbs to unrelated species such as Cladosporium, Memnoniella, Stachybotrys or Ulocladium spp. was unaffected and very common.

Immune complex immunization did not result in species-specific mAbs against P. brevicompactum. The cross-reactivity patterns demonstrate that phylogenetically distant fungi share common epitopes and that these epitopes are expressed at different amounts on a per spore basis by different fungi.