ABSTRACT
Bronchi from guinea pigs actively sensitized to ovalbumin and boosted two weeks later display increased numbers of CD4+ T-lymphocytes and eosinophils. We have further investigated immunopathological changes in sensitized guinea pigs 2 or 24 h after antigenic challenge with ovalbumin. Lungs were resected, frozen and cryostat sections stained with monoclonal antibodies that recognize relevant guinea pig epitopes. Cyanide-resistant peroxidase activity was used to stain eosinophils. No further increase in T-lymphocytes or eosinophils was observed 2 h after challenge. At 24 h, a marked increase in EPO+ eosinophils was found, and this was accompanied by severe mucosal damage characterized by epithelial shedding and ulceration. The numbers of T-lymphocytes remained stable but a novel population of cells with the appearance of dendritic cells was seen in the bronchial wall. They were negative for macrophage markers but were strongly Class II positive. These findings suggest that antigenic challenge results in further recruitment of eosinophils, their activation and release of toxic substances to the epithelium. Furthermore, other cell types, possibly dendritic cells, are attracted to the bronchi and could play a role in maintaining allergic inflammation via antigen presentation.