SPUTUM EOSINOPHILIA AFTER ASTHMATIC RESPONSES INDUCED BY ISOCYANATES IN SENSITIZED SUBJECTS

To assess the nature and the time-course of the cellular component of airway inflammation induced by isocyanates, we examined nine subjects with occupational asthma induced by toluene- or methylene diphenyl-dii socyanate (TDI, MDI) and four control subjects never exposed to isocya nates. Sputum was induced by inhalation of ultrasonically nebulized hy pertonic saline (3-4% NaCl) before and 8, 24, 48 h after inhalation ch allenge with TDI or MDI. Expectorated samples were incubated with dith iothreitol, washed and cytocentrifuged. Differential cell counts were obtained on slides stained with May-Grunwald-Giemsa. Metachromatic cel ls (mast cells and basophils) were counted on slides stained with tolu idine blue at pH 0.1. One occupational asthmatic exhibited a dual reac tion to TDI, two exhibited a single early asthmatic reaction to MDI, s ix exhibited a late asthmatic reaction to TDI (n = 5) or MDI (n = 1), whereas no reactions were observed in control subjects after TDI chall enge. In sensitized subjects eosinophils increased from a median value (interquartile range) of 5 (15)% before challenge to 29 (29)% (P=0.01 4) and to 30 (31)% (P=0.031) 8 and 24 h after TDI/MDI challenges, resp ectively. Sputum eosinophilia was observed both in early and late reac tors and declined to near to baseline values 48 hr after challenge. Pe rcentages of eosinophils in control subjects did not exceed 7% during the study. There was a significant correlation between the increase in eosinophil counts and the magnitude of the bronchoconstriction expres sed as the area of FEV(1) response to isocyanate challenge (rank corre lation coefficient=0.71, P=0.014). No significant changes in sputum ne utrophils, macrophages, lymphocytes and mast cells were detected. The results indicate that isocyanate-induced asthmatic responses are assoc iated with influx of eosinophils in airway secretion lasting up to 24 h.