Immunomodulatory Role of Histamine H2 Receptor in Allergen-Specific Immunotherapy: A Mouse Model of Allergic Rhinitis

Objective. The purpose of this pilot study was to investigate the effects of HR2 on allergen-specific immunotherapy in a mouse model of allergic rhinitis. Study Design. An in vivo study using an animal model. Setting. Catholic Research Institutes of Medical Science. Methods. Fifty mice were divided into 5 groups: control, allergic rhinitis (AR), immunotherapy (IT), immunotherapy with HR2 agonist (HI), and immunotherapy with HR2 antagonist (HB). All mice except for the control group were sensitized with ovalbumin (OVA). After 1 week, mice in the IT, HI, and HB groups underwent immunotherapy by intradermal injections of OVA. During immunotherapy, the HI group was injected with HR2 agonist, whereas the HB group was injected with HR2 antagonist. All sensitized mice were challenged with intranasal OVA. After the final challenge, allergic behavior was evaluated. Interleukin (IL)-13, interferon-gamma, IL-10, and transforming growth factor (TGF)-beta levels in nasal lavage fluid (NALF), as well as OVA-specific IgE levels in serum, were measured. The number of eosinophils in lamina propria was evaluated. Results. The levels of serum OVA-specific IgE and IL-13 in NALF were significantly increased in the HB group compared with the IT group (P < .05). Also, the tissue eosinophil counts were higher in the HB group than in the IT group (P < .05). Conclusion. HR2 antagonist impaired OVA-specific immunotherapy in mice. Although confirmation of this preliminary result is needed, these findings suggest that HR2 receptors may have inhibitory effects on immune tolerance. The authors suggest that application of this property could enhance the efficiency of allergen-specific immunotherapy.