• anhydrides;
  • antibodies;
  • immunologic tests;
  • RAST;
  • ELISA;
  • skin tests

The outcome of immunologic tests of antibodies directed against hapten conjugates of organic acid anhydrides and human serum albumin (HSA) has been studied in workers exposed to phthalic anhydride (PA), methyltetrahydroplithalic anhydride (MTHPA), hexahydrophthalic anhydride (HHPA), and methylhexahydrophthalie anhydride (MHHPA). HSA conjugates of PA, MTHPA, HHPA, MHHPA, and nialeic anhydride (MA) have been prepared and used in the tests. The hapten densities (HD) of the conjugates were varied by different molar ratios of hapten and macromolecule in the preparative procedure. Skin prick reactions to MTHPA-HSA increased with rising HD over the range 6-13 mol/mol. The achieved HD was tested by spectrometric and gas chromatographic methods. In RAST of IgE antibodies MTHPA-HSA with HD six and 25 showed significantly lower bindings than conjugates with intermediate HD. There was a good correlation between skin prick tests and RAST. Of 234 workers tested [MTHPA (n= 145), and HHPA (n= 89)], 45 had a skin prick reaction > 50% of the histamine reaction (1 mg/ml). All but two of these were RAST positive (RAST value > 0.3%; 0.3% upper range in 147 controls; MTHPA, n= 63; HHPA, n= 84). Nine RAST positive workers had no obvious skin prick reaction. However, their RAST values were low (<0.8%). In exposed workers, the ELISA value of specific IgG antibodies to MTHPA-HSA showed optimal values when tested with the HD 13 conjugate. The specific antibodies in workers exposed to either MTHPA or HHPA/MHHPA showed a marked cross-reactivity to MTHPA-HSA, HHPA-HSA, and MHHPA-HSA as proven by skin prick tests, RAST, and RAST inhibition. In workers exposed lo PA (here was less cross reactivity to the other anhydrides.