Absence of IgG antibodies to TDI-HSA in a radioimmunological study

Sera of ninety-one workers with respiratory symptoms related to occupational exposure to toluene diisocyanate (TDI) were tested by a solid phase radioimmunoassay using polyvinyl plates, in an attempt to demonstrate specific IgG antibodies to a conjugate of TDI with human serum albumin (TDI-HSA). Different conjugates were prepared. In our radioimmunoassay a TDI-HSA 1600 (1600 micrograms TDI/mg HSA), obtained at alkaline pH with borate buffer, was used; this conjugate was immunologically reactive and did not contain protein macro-aggregates. No difference in percent of binding of radiolabelled anti-human IgG to TDI-HSA coated on plastic plates was found between exposed workers (asthmatic and non-asthmatic) and fifteen normal subjects. This may suggest that either TDI-induced bronchial asthma is not mediated by IgG antibodies, or TDI-HSA conjugate is unsuitable to be detected by anti-isocyanate IgG.