Age-related changes in interleukin 2 responsiveness of resting and activated human mononuclear cells.

BACKGROUND: Although the "T cell model" on the immunological decline associated with aging is gaining increasing support, the relationship between response to IL2 and aging has not yet been investigated. METHODS: Human peripheral blood mononuclear cells (PBMC) from healthy elderly donors were cultured with increasing concentrations (1-1000 U/ml) of recombinant interleukin 2 (rIL2). RESULTS: PBMC from older donors proliferated as much as those from younger donors until the fifth day of culture, but showed a reduced capability to proliferate in the following days (8th and 10th). Culturing PBMC with PHA we obtained the opposite result. In fact, the known depressed proliferative response of elderly people to the mitogen PHA is detectable only in the early days of culture. Furthermore, the response to rIL2 of 1% or 0.125% PHA-stimulated PBMC showed an important impairment of the proliferative rate in the elderly population with respect to younger controls, although no differences in the number of IL2 receptor-positive cells were detected. This phenomenon was demonstrable mainly in the first several days of culture. CONCLUSIONS: These data suggest a delay in the activation rather than a real functional impairment of PBMC from old donors.