Type IVb Hypersensitivity Reaction in the Novel Murine Model of Palladium–Induced Intraoral Allergic Contact Mucositis

Palladium (Pd) is a component of several alloy types that are widely used in our environment, including several dental alloy types that cause adverse reactions such as hypersensitivity in the oral mucosa. However, the pathological mechanism of intraoral Pd allergies remains unclear because its animal model in the oral mucosa has not been established. In this study, we established a novel murine model of Pd–induced allergies in the oral mucosa, and explored the immune response of cytokine profiles and T cell diversity in terms of the T cell receptor. The Pd–induced allergy mouse was generated by two sensitizations with PdCl(2), plus a lipopolysaccharide solution into the postauricular skin followed by a single Pd challenge of the buccal mucosa. Significant swelling and pathological features were histologically evident at five days after the challenge, and CD4–positive T cells producing high levels of T helper 2 type cytokines had accumulated in the allergic oral mucosa. Characterization of the T cell receptor repertoire in Palladium allergic mice indicated that Pd–specific T cell populations were limited in V and J genes but were diverse at the clonal level. Our model demonstrated that a Pd–specific T cell population with Th2 type response tendencies may be involved in the Pd–induced intraoral metal contact allergy.