Experimental study on respiratory sensitivity to inhaled toluene diisocyanate

Groups of guinea pigs were exposed via inhalation to toluene diisocyanate (TDI) ranging from 0.02 to 1.0 ppm for 3 h/day on 5 consecutive days. Three weeks later, guinea pigs were challenged with TDI-GSA conjugates. Evaluations were based on TDI specific antibodies, pulmonary response and antigen stimulated histamine release from lung mast cells (LMC). The results indicated that both the antibody titer and the severity of pulmonary response followed a concentration-dependent pattern, with corresponding threshold levels. Antibodies and pulmonary responses were undetectable in animals exposed to 0.02 ppm TDI; however, exposure to 0.2 ppm TDI resulted in significant antibody production and pulmonary responses. Animals showed higher antibody titers and more severe pulmonary responses as TDI concentration increased from 0.6 ppm to 1.0 ppm. A discrepancy which was noted between antibody production and pulmonary responses was thought to be relevant to the discrimination of the potentials of antigen stimulated histamine release from LMC mediating between these two responses.