Mast cells in the airway mucosa and rapid development of occupational asthma induced by toluene diisocyanate.

We examined lobar bronchial biopsies taken from 18 subjects with occupational asthma induced by toluene diisocyanate (TDI) and from nine nonasthmatic control subjects. Two groups of asthmatics were identified on the basis of the duration of exposure to TDI before the onset of symptoms of asthma. Group A (n = 8) developed asthma after 2.4 +/- 0.4 yr of exposure to TDI, and Group B (n = 10) developed asthma after 21.6 +/- 3.1 yr of exposure to TDI. Both groups of asthmatic subjects had increased numbers of inflammatory cells in the airway mucosa compared with subjects in the nonasthmatic control group. Comparison between Groups A and B showed that subjects who developed asthma after short-term exposure had a significantly increased number of mast cells both in epithelium and in lamina propria than did subjects who developed asthma after long-term exposure to TDI (p < 0.01). Interestingly, the numbers of mast cells both in the epithelium (rs = -0.52, p < 0.05) and in the lamina propria (rs = -0.81, p < 0.001) were inversely correlated with the length of exposure to TDI before the onset of asthma. In conclusion, subjects who develop asthma after short-term exposure to TDI have an increased number of mast cells in the airway mucosa, suggesting that these cells may be associated with individual susceptibility differences to offending agents.