Immunity to cancer. Naturally occurring tumours in domestic animals as models for research. 1.

PREVENTIVE VACCINATION IS SUCCESSFULLY PRACTISED TODAY AGAINST TWO NEOPLASTIC DISEASES OF DOMESTIC ANIMALS: fibropapillomatosis of cattle and Marek's disease of chickens (a lymphoproliferative disease). Also it may soon be possible to immunize cats against lymphosarcoma. This memorandum describes these diseases and the immunological reactions involved. It also mentions a number of other tumours that could be used for immunological studies.The greatest advances in immunity have been made with the tumours caused by viruses. The killed papillomavirus vaccine used against bovine papillomatosis produces demonstrable antibodies against the virus. In the case of Marek's disease of chickens, which is due to a herpesvirus, a live virus vaccine is used. This does not prevent infection with virulent virus, but prevents the development of neoplasia. The mechanism by which the vaccine produces its effect is not yet known. Immunization with live and with killed vaccines has been successfully carried out experimentally against leukosis of chickens, which is caused by an oncornavirus. There is evidence that it will be possible to vaccinate cats against lymphosarcoma with non-living vaccine.Naturally occurring cancer in domestic animals parallels cancer in man more closely than does experimentally induced cancer in inbred laboratory animals; therefore immunological studies with the former are more likely to yield results relevant to the problem in man. Experimental cancer in rodents provides models that have the great advantages of uniformity and availability, and they cannot be replaced. However, models in domestic animals offer valuable supplementary systems for research aimed at elucidating the basic principles of immunity to cancer.