Immunoglobulin E-mediated asthma and hypersensitivity pneumonitis with precipitating anti-hapten antibodies due to diphenylmethane diisocyanate (MDI) exposure.

Two workers are presented who were exposed to diphenylmethane diisocyanate (MDI) while coating pipes with a polyurethane foam. After a latent period of exposure, worker A developed immediate-onset asthma and worker B developed a clinical picture of hypersensitivity pneumonitis for which he was hospitalized. The antibody response of these workers to a conjugate of MDI with human serum albumin (MDI-HSA) was measured by gel precipitation, total antibody binding of 125I MDI-HSA, and specific IgG and IgE antibody by polystyrene-tube radioimmunoassay (PTRAI). Worker B had precipitating antibody to MDI-HSA by double immunodiffusion in gel. Both workers had high levels of IgG antibody specific for MDI-HSA which had some cross-reactivity with a conjugate or toluene diisocyanate and HSA. Total serum antibody binding of 125I MDI-HSA was 15 microgram/ml in worker A and 900 microgram/ml in worker B. Both workers had serum IgE antibody specific for MDI-HSA as measured by two PTRIA techniques. These results indicate that a marked immunologic response to MDI is possible in exposed workers and that hypersensitivity pneumonitis can occur subsequent to the inhalation of a low-molecular-weight chemical in the industrail setting.