The effect of active immunization of rats with heterologous alpha-fetoprotein upon hepatocarcinogenesis induced by 3'-methyl-4-dimethylaminoazobenzene.

Immunization of rats with a purified mouse alpha-fetoprotein (AFP) suspended in Freund's complete adjuvant resulted in the production of antibodies that could precipitate both mouse and rat AFPs. A group of rats was immunized first and then fed a diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) for 10 weeks. In these rats the elevation of serum AFP as well as the development of hepatoma were markedly inhibited. Another group of rats was immunized after feeding the diet containing 3'-Me-DAB for 10 weeks. The development of hepatoma and production of serum AFP were also suppressed. In both groups the life span of the rats was prolonged by the immunization.