Human lung mast cells and pulmonary macrophages produce tumor necrosis factor-alpha in sensitized lung tissue after IgE receptor triggering.

Tumor necrosis factor (TNF) is considered to play a key role in the pathogenesis of allergic disorders. We examined TNF production in human lung fragments after IgE receptor triggering at mRNA and protein levels. IgE receptor triggering was performed by sensitizing lung fragments with monoclonal human IgE and then exposing them to anti-human IgE antibody. Cytotoxic activity against L929 cells appeared in the culture supernatant of lung fragments 2 h after IgE receptor triggering and increased for up to 4 h. This cytotoxic activity was completely neutralized by anti-human TNF antibody. Northern blot analysis demonstrated that 1.8-kb TNF mRNA transcripts in sensitized lung fragments were expressed as early as 1 h after IgE receptor triggering and continued up to 4 h. Immunohistochemical analysis revealed TNF localization in tissue mast cells, alveolar macrophages, tissue macrophages, and bronchial epithelial cells. Double staining with anti-TNF antibody and alcian blue clearly identified that lung mast cells are one of the TNF-positive cell types in the pulmonary tissue. With immunoelectron microscopy, TNF immunoreactivity was detected in the rough endoplasmic reticulum and the perinuclear spaces in tissue macrophages, and in the cytosol and the perinuclear spaces in bronchial epithelial cells. In addition, IgE was detected on the cell surface of mast cells, tissue macrophages, and alveolar macrophages. These results suggest that TNF is released from mast cells and pulmonary macrophages through IgE receptor triggering and may play a key role in the allergic reaction in human airway.