A Perspective on Cellular Immunity in the Elderly

The increased incidence of infection and malignancy in elderly individuals has prompted many studies that demonstrate that the aging immune system is impaired. Most of these studies have focused on the impairment of acquired immunity provided by lymphocytes. While defects in acquired humoral and T-cell-mediated immunity may exist, increased susceptibility to infection may result from defects in the constitutive functioning of macrophages and granulocytes. Recognition of the potential importance of defects in constitutive immunity in the elderly may provide new opportuni-ties for therapeutic and prophylactic intervention in this population. There is considerable epidemiological evidence that the inci- Most of the research on cell-mediated immunity in the el-derly has used either human or murine systems to define indence of both infections [1–4] and cancers [5, 6] increases with age. Efforts to characterize immune defects underlying vitro and in vivo defects in T cell function. Miller [7] described decreased proliferative responses to T cell mitogens, whichthis increased susceptibility of the aged have focused on readily measurable parameters of acquired immune function, particu- may be related to altered signal transduction pathways [12, 13] or to alterations in the production of [14, 15] and respon-larly on deficits in T cell function. The critical role of macro-phages and granulocytes in primary resistance to infection dic- siveness to [16] IL-2. While numbers of both memory and naive T cells may be decreased in elderly subjects, the relativetates a need to reevaluate the importance of defects in thes