Antibody formation to dog pulp tissue altered by formocresol uithin the root canal

After pulpal extirpation of twenty teeth in each of five dogs, these animals were primarily immunized intramuscularly by combining formocresol with the dog's own pulp (three dogs), saline solution with pulp (one dog) and injecting sheep erythrocytes (one dog). A sixth dog was used as a control for the Arthus skin test. Secondary immunizations were accomplished via the root canal every 7 days over a 28-day period. Arthus skin-test reactions demonstrated less of a response to the formocresol alone than when the dogs' pulp was conbined with this material. In vitro analysis of hemagglutinating antibody titer showed a tremendous increase when pulp was incubated with formocresol as compared to the saline-treated pulp. Therefore, dogs' pulp tissue became antigenically altered by the formocresol recognized by the host, and a specific humoral response resulted.