Another Look at Immunologic Surveillance

THE idea that the immune response is the principal defense against neoplastic cells has had a profound influence on cancer research, particularly during the past decade. Soon after its explicit formulation by Thomas,1 Burnet2 elaborated this concept into a theory that he termed immunologic surveillance. Its central theme is that ordinarily an immune response destroys cancer cells while they are still in the incipient stage of tumor formation. Both Thomas and Burnet reasoned that malignant cells should differ antigenically from normal cells and thereby elicit a protective immunologic reaction, perhaps of the same type that destroys grafts of foreign cells. . . .