The cumulative activity of benzo(a)pyrene on systemic immune responses with mite allergen extract after intranasal instillation and ex vivo response to ovalbumin in mice.

The cumulative activity of benzo(a)pyrene (BP) as one of the polycyclic aromatic hydrocarbons which is present in diesel exhaust particles on systemic immune responses was studied in mice after intranasal instillation and in vitro exposure to allergens. The main purpose was to elucidate whether BP has an adjuvant effect in this responses or not. Male Balb/cA mice were immunized with mite allergen extract (MAE) either alone or in combination with BP. Controls were given BP, or buffer alone. The animals were immunized four times. One week after the last immunization, anti-MAE IgE antibody in serum and IL-4, IL-10, IL-12p70 and IFN-gamma secreted by spleen cells upon rechallenge with the same allergen, was measured by ELISA. An increased response to the antigen was observed in animals receiving MAE together with BP, compared with animals receiving MAE alone. In another attempt, bone marrow-derived dendritic cells (DCs) are obtained from naive male Balb/c mice and were exposed to the varying doses of ovalbumin (OA) and BP. There were four groups of study: control, BP, OA and OA plus BP. An elevated response was observed in animals receiving OA together with BP, compared with animals receiving OA alone. In conclusion, this work shows that BP has an cumulative activity for specific IgE and Th1/Th2 cytokines production after intranasal instillation and cytokine secretion by DCs after in vitro exposure, and this phenomenon is dose-dependent. Thus, it may be another evidence on immunomodulatory effect of dendritic cells.