TDI-induced Asthma and Immune Responses in TDI-exposed Workers

Abstract

Background: Toluene diisocyanate (TDI) is known to be the most common cause of occupational asthma (OA) in Korea. Although TDI can elicit humoral immune responses including specific-IgE (sIgE) and specific-IgG (sIgG) responses, the exact role of these immune responses has not been clearly clarified yet. Objective: This study was carried out to estimate the prevalence of TDI-induced OA, and to evaluate the clinical significance of TDI-related humoral immune responses in currently TDI-exposed workers. Method: Questionnaire interview for respiratory symptoms was conducted to 170 workers with direct exposure to TDI (exposed group). After screening survey, workers with suspected occupational asthma were selected for methacholine and TDI bronchial provocation tests (BPTs). Serum sIgG and sIgE antibodies to TDI-HSA conjugate, and sIgG to cytokeratin (CK) 8, 18, and 19 were detected by enzyme- linked immunosorbent assay in 170 exposed workers, and compared with 61 unexposed workers in the same workplace (unexposed group) and 75 unexposed healthy controls(healthy control group). Result: Eleven (6.9%) among 170 workers complained symptoms of OA, and 7 of 11 symptomatic workers showed positive airway hyperresponsiveness to methacholine (4.1%). One worker with spray-painting job was confirmed as having TDI-induced asthma by showing positive responses to both methacholine and TDI BPTs. The prevalence of sIgG to TDI-HSA conjugate was significantly higher in TDI-exposed workers (10.1%) than in unexposed workers (0%) and healthy control (2.7%). However, no significant difference was noted between symptomatic (18.2%) and asymptomatic workers (9.5%) among the exposed group. The prevalences of sIgE to TDI-HSA conjugate and sIgG to CK 8, 18, 19 were not significantly different between the three groups. Conclusion: The prevalence of TDI-induced OA was noted to 0.58% in the current working environments. The clinical significance of TDI-induced humoral immune responses may be clarified by further prospective studies.