Molecular changes associated with increased TNF-α-induced apoptotis in naïve (TN) and central memory (TCM) CD8+ T cells in aged humans

Abstract

Background: Progressive T cell decline in aged humans is associated with a deficiency of naïve (TN) and central memory (TCM) T cells. We have previously reported increased Tumor necrosis factor-α (TNF-α)-induced apoptosis in TN and TCM T cells in aged humans; however, the molecular basis of increased apoptosis remains to be defined. Since expression of TNF receptors (TNFRs) was reported to be comparable in young and aged, we investigated signaling events downstream of TNFRs to understand the molecular basis of increased TNF-α-induced apoptosis in aged TN and TCM CD8+ cells. Results: The expression of TRAF-2 and RIP, phosphorylation of JNK, IKKα/β, and IΚBα, and activation of NF-ΚB activation were significantly decreased in TN and TCM CD8+ cells from aged subjects as compared to young controls. Furthermore, expression of A20, Bcl-xL, cIAP1, and FLIP-L and FLIP-S was significantly decreased in TN and TCM CD8+ cells from aged subjects. Conclusions: These data demonstrate that an impaired expression/function of molecules downstream TNFR signaling pathway that confer survival signals contribute to increased apoptosis of TN and TCM CD8+ cells in aged humans.