Immunobiology of aging and cancer

Although the incidence of neoplasms is increased in the elderly, some tumors appear to grow more slowly in old as compared to young patients. We have used the B16 melanoma to explore the relationship between age, T-lymphocyte function, and the rate of tumor growth. Increasing age is associated with a decreased rate of tumor growth and impaired T-cell function in C57BL/6 mice. Furthermore, when T-cell immunity in young mice is compromised by thymectomy, B16 tumor growth is decreased. Mixed cell transfer studies demonstrated that T cells from young but not old donors stimulate the growth of B16 melanoma cells in young lethally irradiated recipients. Recently, T cells from young but not old mice have been reported to produce angiogenic factors. As tumors from young mice have a richer vascular supply than in old mice, it appears that one mechanism for the age-associated decrease in B16 melanoma growth is the decreased capacity of T cells from old mice to generate angiogenic factors. However, parabiosis of young and old mice showed that local factors in old mice also limit the stimulatory influences of T cells from young mice. Novel therapeutic approaches to limit the growth of tumors might result from a greater understanding of the production of and response to angiogenic factors produced by T cells.