ABSTRACT
Recent studies have supported the long-suspected belief that the immune system surveys for antigens associated with a newly developing tumor, and destroys the cells bearing them. Evidence supportive of this possibility comes from the observation of increased 282tumor incidence in immunodeficient animals or humans. However, congenitally athymic mice do not have high tumor rates, suggesting that the T-cell system may not be the major player in surveillance of certain tumors. Moreover, congenitally immunodeficient and immunosuppressed patients have high rates of tumors only of lymphoid or epithelial cells. Thus, a less-specific tumor surveillance system, perhaps NK cells, may predominantly search for and eliminate certain types of tumor cells early in their development. The best evidence for a surveillance mechanism involving T cells comes from experimental mouse models with virus-induced tumors, but here the response is essentially directed to viral antigens and not tumor antigens.
