High circulating levels of tumor necrosis factor-alpha in centenarians are not associated with increased production in T lymphocytes

BACKGROUND: Aging is characterized by increased inflammatory activity reflected by increased plasma levels of proinflammatory cytokines, concomitant with an altered cytokine profile of T lymphocytes. High plasma levels of tumor necrosis factor (TNF)-alpha are strongly associated with morbidity and mortality in elderly humans. However, the cellular source and mechanisms for the increased circulating TNF-alpha levels are unknown.

OBJECTIVE: The aim of the present study was to investigate if high plasma levels of TNF-alpha are associated with increased production of TNF-alpha by T lymphocytes in elderly humans.

METHODS: TNF-alpha production by CD4+ and CD8+ T lymphocytes was measured by flow cytometry following stimulation with phorbol 12-myristate 13-acetate and ionomycin in 28 young controls, 14, 81-year-olds and 25 centenarians.

RESULTS: Plasma levels of TNF-alpha increased with increasing age. An increased percentage and number of T lymphocytes from the 81 year olds expressed TNF-alpha, whereas centenarians did not show this altered TNF-alpha secretion profile.

CONCLUSION: T cells may contribute to the elevated levels of plasma TNF-alpha in healthy elderly subjects, whereas other mechanisms are responsible in very old individuals.