Age-related changes in immunologic and hormonal activities.

: The immune system has been a focus of intensive gerontological research, because it appears to be involved in many deleterious diseases associated with ageing, including cancer, and because the likelihood of successful therapeutic strategies for altered immune functions in the elderly is high. Research efforts have been centred on two levels of biological complexity--the cell and the organism. At the cellular level, emphasis has been on the nature of the alteration in immune functions with age, and, at the level of the organism, whether the diseases associated with immunological dysfunction of elderly individuals can be controlled by immunomodulation. We discuss age-related changes at the cellular level with emphasis on qualitative changes in the antigen/mitogen responsive cells with respect to production of and response to hormones. We then consider whether ageing 'hot spots' exist along the differentiation vector of antigen/mitogen responsive cells; i.e., whether immune cells are vulnerable to ageing only at certain stages of their differentiation processes. We conclude by considering the use of tissue grafting and chemical treatment, the two most encouraging methods of immunopotentiation at the level of the organism, as an option in modulating resistance of old individuals to cancer.