The efficacy of an “allergen–gene immunization protocol” in altering allergic response was examined. Intramuscular injection of rats with a plasmid DNA encoding a house dust mite allergen into the muscle results in its long–term expression and the induction of specific immune responses. Significantly, this approach prevents the induction of immunoglobulin E synthesis, histamine release in bronchoalveolar fluids, and airway hyperresponsiveness in rats challenged with aerosolized allergen. Furthermore, this suppression is persistent and can be transferred into naive rats by CD8⁺ T cells from gene–immunized rats. These findings suggest that allergen–gene immunization is effective in modulating allergic responses, and may provide a novel therapeutic approach for allergic diseases.