Expression of interleukin (IL)-4 and IL-5 proteins in asthma induced by toluene diisocyanate (TDI).

BACKGROUND: TDI-induced asthma exhibits clinical, functional and morphological similarities with allergen-induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDI. In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T-cell clones derived from bronchial mucosa of subjects with TDI-induced asthma produced IL-5 and interferon-gamma, but not IL-4, upon in vitro stimulation. OBJECTIVES: To investigate in vivo the role of IL-4 and IL-5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies. METHODS: We obtained bronchial biopsies from six subjects with TDI asthma 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1-4 weeks after the last exposure to TDI (chronic group), and in six non-asthmatic controls. The number of eosinophils, mast cells, T-lymphocytes, and IL-4 and IL-5 protein positive cells was determined by immunohistochemistry in the area 100 microm beneath the epithelial basement membrane. RESULTS: The characteristic increase of submucosal eosinophils, but not of mast cells and T-lymphocytes, was observed in the subjects with TDI-induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI-induced asthma, cell immunoreactivity for IL-5 was increased when compared with normal controls. There was no difference in the expression of IL-5 protein between challenged and chronic asthmatics. In contrast, the expression of IL-4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI. CONCLUSIONS: We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL-4 and IL-5, whereas chronic TDI asthma was associated with increased expression of IL-5, but not of IL-4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL-5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH2-like cytokines in TDI-induced asthma may not always be co-ordinately regulated in vivo.

Cytokines in the airway mucosa of subjects with asthma induced by toluene diisocyanate.

To determine the status of activation of lymphocytes and the role of cytokines on the inflammatory response of the bronchial mucosa in toluene diisocyanate (TDI) asthma, we performed a quantitative analysis of bronchial biopsies obtained from 15 subjects with TDI-induced asthma and seven normal control subjects. Markers of activation of lymphocytes (CD25 and Very Late activation Antigen-1, VLA-1) and expression of Tumor Necrosis Factor-alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) were determined by immunohistology in the submucosa. Moreover, expression of adhesion molecules on endothelium of submucosal vessels was assessed. Asthmatic subjects had increased numbers of cells expressing CD25 and VLA-1 compared with the control group (p < 0.05). TNF alpha and IL-1 beta immunoreactivity was increased in asthmatics compared with control subjects (p < 0.01), whereas the expression of adhesion molecules, ICAM-1 and E-selectin, on vascular endothelium was not significantly different. No significant differences in the morphologic quantifications were observed between the asthmatics who had biopsies taken 2 d after TDI challenge (n = 7) and those with longer interval (21 +/- 8 d) between TDI challenge and biopsy (n = 8), suggesting that the increase in CD25, VLA-1, TNF alpha, and IL-1 beta was not due to an acute effect, but could be considered a part of the chronic inflammatory process of the airways. We conclude that the inflammatory response of the airways in TDI-induced asthma is characterized by persistent activation of lymphocytes and by chronic expression of proinflammatory cytokines.