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Intracellular free Ca2+ fluxes and responses to phorbol ester in T lymphocytes from healthy elderly subjects

A group of healthy elderly subjects (≥75 years) was selected by the strict criteria of the SENIEUR protocol, and compared with healthy young (≤35 years) volunteers. Mitogenic responses of peripheral blood mononuclear cells to phytohaemagglutinin and anti‐CD3 were significantly reduced in the elderly (P <0.0002), thereby confirming that even though in perfect health, elderly individuals show impaired cell‐mediated immunity. However, no abnormality of intracellular free Ca2+ fluxes could be detected in purified T cells from the elderly subjects when stimulated with anti‐CD3 antibody. Nevertheless, both the proliferative responses of purified T cells to phorbol ester and calcium ionophore (Ionomycin) and the phorbol ester‐induced inhibition of the Ca2+ response were defective in the elderly subjects (p <0.003 and p < 0.0002, respectively). These data suggest that signal transduction and the generation of second messengers proceed normally in T cells from the elderly, but downstream events mediated by activation of protein kinase C are dysfunctional.