Bronchial epithelial cells exposed to isocyanates potentiate activation and proliferation of T-cells

Bronchial epithelial cells release chemotactic factors for lymphocytes and express HLA-DR antigens. Thus they may contribute to the T-cell-mediated inflammatory responses involved in a number of pulmonary diseases such as asthma. In this study, the in vitro exposure of human bronchial epithelial cells to toluene 2,4-diisocyanate (TDI), an inflammatory and asthmogenic stimulus presumed to act at least in part through immunological mechanisms, provoked cell damage followed by proliferation of the cells that survived the injury. At the time of the proliferative response, epithelial cells released factors that upregulated the activation and proliferation of T lymphocytes presensitized by antigen receptor triggering. The T-cell activating factors were interleukin (IL) 1- and 6-like substances, as demonstrated by the ability of specific antisera to inhibit most of the biological effect, and by the ability of recombinant IL-1 and IL-6 to reproduce it. Appreciable amounts of immunoreactive IL-1 and IL-6 were indeed recovered in the supernatants of TDI-exposed epithelial cells. The release of these cytokines may represent an important mechanism by which epithelial cells respond to some environmental stimuli and contribute to the persistence of inflammatory responses in the airways.