[An immunological study of workers exposed to diphenylmethane diisocyanate (MDI)]

The average (OD values) and positive rates of specific IgE antibodies to a MDI-human serum albumin (HSA) conjugate in 25 workers exposed to MDI were significantly lower than those in 8 subjects of MDI asthma, while they were significantly higher than those in the 30 control subjects who had never bee exposed to MDI before. The positive rates of specific IgE antibodies in symptomatic MDI-workers were significantly higher than those in asymptomatic MDI-workers. The results of studies of specific IgE antigenic inhibition of serum ELISA activity confirmed the antigenic specificity to MDI-HSA. The average levels and positive rates of serum total IgE in 25 MDI-workers significantly increased when compared with 30 non-exposed subjects; while no significant difference when compared with 8 subjects of MDI asthma. Agreement rates of specific IgE were 85.7% with skin-prick test. The percentage of the acid alpha-naphthyl acetate esterase activity in T-cell of peripheral blood showed no statistically significant difference in all 3 groups. The results of the study suggested that the level of specific IgE was related to exposure to MDI and IgE mediated response played an important role in the allergic mechanism due to MDI, while it was not related to cell-immunological response.