Selectivity of IgE Responses, Mast Cell Sensitization, and Cytokine Expression in the Immune Response of Brown Norway Rats to Chemical Allergens

Sensitizing chemicals can induce various types of allergic disease, including contact dermatitis and occupational asthma. In the present study we have examined the nature of the immune response induced in Brown Norway (BN) rats by oxazolone (OX), a potent contact allergen, and by trimellitic anhydride (TMA), a chemical known to cause sensitization of the respiratory tract and occupational asthma. BN rats were exposed topically to either OX or TMA at doses selected to achieve similar levels of proliferative activity by draining LNC. Both chemicals stimulated hapten-specific IgG antibody responses, but only TMA induced specific IgE antibody, an increase in total serum IgE, and active sensitization of mast cells. Draining LNC from OX-treated rats expressed elevated IFN-γ mRNA, whereas those from TMA-treated rats expressed elevated IL-5 mRNA compared to controls. Furthermore, Con A-activated draining LNC from rats exposed to TMA, but not OX, released significantly increased concentrations of IL-4. In conclusion, different chemical allergens can induce in the BN rat divergent patterns of IgE response and cytokine expression.