Aging and lymphokine production by T cell subsets.

From sexual maturity to old age, the mammalian immune system undergoes progressive changes, some of which may predispose individuals to infectious, neoplastic and degenerative diseases. These age-associated changes are prominent in the T lymphocyte compartment and encompass both the CD4+ and CD8+ T cell subpopulations. In this review, we focus on the mouse model system and summarize current information on the existence of functionally distinct subsets within each of the CD4+ and CD8+ cell subpopulations. We describe how the representation of these subsets is altered during the aging process, with consequent changes in the lymphokine production repertoires and other functional attributes of the T cell pool. Lastly, we present evidence showing that similar changes occur in aging humans and discuss the potential impact of these changes on immune responsiveness in late life.