Effect of allergen-specific immunotherapy on interleukin-4, interleukin-5 and interferon-gamma mRNA expression in the nasal mucosa of rats with allergic rhinitis.

To elucidate the mechanism of immunotherapy, we tested the effect of ovalbumin and ovalbumin-pullulan conjugate immunotherapy on the expression of interleukin (IL)-4, IL-5 and interferon-gamma (IFN-gamma) mRNA in the nasal mucosa of sensitized rats. Forty-five rats were injected with ovalbumin intraperitoneally on three consecutive days and later were exposed to ovalbumin aerosol. The rats were injected intradermally, on six consecutive days, with saline, ovalbumin or ovalbumin-pullulan conjugate. Later, nasal mucosa was obtained and reverse transcription-polymerase chain reaction (RT-PCR) was performed. Nasal responses and specific immunoglobulin E (IgE) were measured. Although the immunotherapy significantly decreased nasal airway resistance, dye leakage and histamine content in nasal irrigation after allergen challenge, no significant difference was found in IL-4 and IL-5 mRNA expression or in specific IgE level among the three groups. We conclude that in this allergic model, the improvement of nasal responses after immunotherapy was the result of a mechanism other than decrease of T-helper 2 (Th2) cytokines.