Di-(2-ethylhexyl) phthalate possesses an adjuvant effect in a subcutaneous injection model with BALB/c mice.

The prevalence of allergic airway diseases is rapidly increasing in Western Europe and North America and the introduction of anthropogenic chemicals may explain a part of this increase. Recently, our group found that degradation products from several commonly used phthalate plasticizers possess adjuvant activity in an animal model. Mono-2-ethylhexyl phthalate, which is the degradation product of di-(2-ethylhexyl) phthalate (DEHP), was among these substances. These findings prompted the study of the adjuvant activity of the parent compound itself. Thus, DEHP was studied in a model using ovalbumin (OA) as the model antigen. OA was injected subcutaneously in the neck region of BALB/cJ mice with or without DEHP. The levels of OA-specific IgE, IgG1 and IgG2a antibodies in sera were measured by ELISA. Adjuvant effect, defined as a statistically significant increase in antibody level, was observed with IgG1 at a concentration of 2000 microg DEHP/ml after both one and two boosters.