Aspergillus antigen-induced eosinophil differentiation in a murine model.

Eosinophilia is a prominent feature of the cellular response in allergic and parasitic diseases. Allergic bronchopulmonary aspergillosis due to colonization of the lungs of some asthmatics with Aspergillus fumigatus is characterized by high levels of serum immunoglobulin E and peripheral blood (PB) and lung eosinophilia. This study investigates the role of eosinophils in the pathogenesis of allergic bronchopulmonary aspergillosis by using a mouse model. BALB/c mice were immunized intranasally and intraperitoneally with A. fumigatus antigens (Ag), and the eosinophils in PB and bone marrow (BM) were enumerated. Eosinophilopoiesis in BM cultures was studied in the presence of murine recombinant interleukin-5 (mrIL-5) and supernatants from pokeweed mitogen-stimulated spleen cells as the source of eosinophil differentiation factors. Eosinophils were quantitated by direct counting and by estimating eosinophil peroxidase activity. The results indicate that the percentage of eosinophils in the PB (5.77 +/- 1.17) and the BM (11.19 +/- 4.31) of mice exposed to A. fumigatus Ag was higher than in controls (PB, 2.42 +/- 0.76; BM, 5.12 +/- 2.79; P less than 0.01 for both). Similarly, a significant increase in eosinophils was observed in the BM population from mice exposed to A. fumigatus Ag compared with that in controls when cultured with murine recombinant interleukin-5 (23.13 +/- 7.14 versus 13.77 +/- 5.79, P less than 0.01), indicating that the mice exposed to A. fumigatus Ag had significantly greater numbers of eosinophil precursors in their BM. This study demonstrates that A. fumigatus Ag may be involved in the in vivo commitment of stem cells in the eosinophil differentiation pathway.