Experimentally induced alterations in periapical tissues of the cat.

Ten cats were immunized with subcutaneous injections of keyhole limpet hemocyanin (KLH). After it was determined that the experimental animals had developed circulating antibodies to KLH, challenge doses of KLH were administered via the root canal system. The radiographic and histologic findings suggest that antigen-antibody complex reactions can occur in periapical tissues of teeth, and that they can play a role in the pathogenesis of periapical lesions. In contrast, no radiographic and histologic changes were noted in non-immunized cats.