The characteristics of specific IgG to phthalic anhydride (PA)-albumin conjugate

Phthalic anhydride (PA), used in the chemical industry, binds to proteins and causes allergic reactions. It is important to study the characteristics of antibody to PA-protein. We produced specific IgG against PA-rabbit serum albumin (RSA) by administering subcutaneous injections of PA-RSA conjugate to two rabbits. Both rabbits' sera had high titers of IgG not only to PA-RSA but also to PA-human serum albumin (HSA) and HSA. In enzyme-linked immunosorbent assay (ELISA) and ELISA HSA inhibition, specific IgG to PA-HSA revealed cross-reactivity to three other phthalyl anhydride conjugates, hexahydrophthalic anhydride (HHPA)-HSA, methylhexahydrophthalic anhydride (MHHPA)-HSA, and methyltetrahydrophthalic anhydride (MTHPA)-HSA, in both sera. Titers of IgG to HHPA-HSA, MHHPA-HSA, and MTHPA-HSA were not significantly different. On affinity chromatography, highly specific IgG to PA hapten alone was purified. In the serum not binding to PA column, specific IgG to PA-HSA was significantly less than in original serum, but levels of specific IgG to other phthalyl anhydride-HSA were unchanged. Rabbits immunized with PA-RSA produced at least two types of IgG: one is to PA hapten alone and the other may be against new antigenic determinants (NADs) on HSA.