Apoptosis and reduced influenza A virus specific CD8+ T cells in aging mice

Some studies have reported increased apoptosis in CD8+ T cells from aged mice. We previously demonstrated diminished virus-specific CD8+ cytotoxic T lymphocyte (CTL) activity in aged mice in comparison to young mice. The present study investigated the role of apoptosis in age-related influenza virus-specific CD8+ CTL deficiency. Splenocytes from influenza-primed aged and young mice were stimulated in vitro with virus. The CD8+ T cell/total lymphocyte ratios correlated with CTL activity and were significantly decreased and increased in aged and young mice, respectively. Fas, FasL, TNF-α and TNFR-p55 expression, measured by flow cytometry, ELISA and/or RT–PCR, were significantly elevated in aged mice. Apoptotic CD8+ T cells (Annexin V binding) were also elevated in aged mice. IL-12 treatment increased CD8+ CTL activity and IFN-γ production but did not affect apoptosis. Thus, apoptosis may contribute to reduced influenza virus-specific CD8+ T cell frequency, CTL deficiency and increased influenza disease in aging.