Blood T-lymphocyte functions in healthy adults in relation to age.

Blood T-lymphocyte functions were studied in 167 healthy adults (age range 19-91 years). Lymphocyte DNA synthesis induced by concanavalin A, pokeweed mitogen and PPD antigen declined with age while the spontaneous DNA synthesis remained essentially unchanged. Relative and total T-cell counts but not total lymphocyte counts were moderately decreased in elderly persons. The lymphocyte response to mitogens correlated with the PPD-induced activation in vitro. Lymphocyte and T-cell counts did not show any association with the response to mitogens and antigen. A few subjects were tested on several occasions during 2-7 years confirming a good reproducibility of the techniques employed. Thus ageing is associated with diminished number of T-cells and impairment of lymphocyte activation by T-cell mitogens and PPD antigen. The clinical importance of this general age-related T-cell deficiency remains largely unresolved.