Conclusions
Endotoxin augments the allergic inflammation in the lungs of individuals with asthma, and induces an enhanced influx of monocytes and functionally active antigen-presenting mDCs into the respiratory tract.
Methods
Seventeen subjects with mild allergic asthma underwent segmental challenge with allergen, endotoxin, and the combination of both in three different lung segments via bronchoscopy. The cellular influx including monocytes, myeloid dendritic cells (mDCs), and plasmacytoid dendritic cells (pDCs), as well as the level of cytokines, were assessed in bronchoalveolar lavage fluid obtained 24 hours after segmental challenge. Monocytes, mDCs, and pDCs were isolated and their capacity to induce T cell proliferation was determined. Measurements and main
Results
Endotoxin enhanced the cellular response to allergen. The combination of allergen and endotoxin resulted in increased numbers of total cells, lymphocytes, neutrophils, eosinophils, monocytes, and mDCs, as well as increased levels of lipopolysaccharide-binding protein, IL-1alpha, IL-6, and tumor necrosis factor-alpha in the bronchoalveolar lavage fluid compared with allergen alone. Isolated mDCs but not pDCs induced a strong T cell proliferation in vitro. Conclusions: Endotoxin augments the allergic inflammation in the lungs of individuals with asthma, and induces an enhanced influx of monocytes and functionally active antigen-presenting mDCs into the respiratory tract.