Aging affects responsiveness of peripheral blood mononuclear cells to immunosuppression of periodontal ligament stem cells

Objectives The effect of age on the response of peripheral blood mononuclear cells (PBMCs) to immunosuppression induced by human periodontal ligament stem cells (hPDLSCs) is unclear. The identity of the cytokines most effective in inducing the PBMC immune response remains unknown. This study investigated the effects of age on immunophenotype, proliferation, activation, and cytokine secretion capacities of PBMCs following co-culture with hPDLSCs. Methods PBMCs were collected from younger (16-19 years) and older (45-55 years) donors, then co-cultured with confirmed hPDLSCs for various lengths of time. T lymphocyte proliferation and cell surface marker expression were analyzed by flow cytometry. Cytokine expression levels were measured by quantitative polymerase chain reaction assays and enzyme-linked immunosorbent assays. Results CD28 expression by T lymphocytes decreased with age, indicating reduced proliferation; CD95 expression increased with age, indicating enhanced apoptosis. Moreover, hPDLSCs inhibited T lymphocyte proliferation in both age groups; this inhibition was stronger in cells from older donors than in cells from younger donors. Age reduced the secretion of interleukin-2 and interferon-gamma, whereas it increased the secretion of tumor necrosis factor-beta by PBMCs cultured with hPDLSCs. Conclusions Aging may have a robust effect on the response of PBMCs towards hPDLSC-induced immunosuppression.