Figure 1

CD4 but not CD8 T cell decay in secondary lymphoid organs during ageing. (A) Total CD4 and CD8 T cell numbers recovered from pooled spleen and lymph nodes. Numeration and FACS analyses of secondary lymphoid organs were performed on young (2–6 months (Y); n = 30), middle-aged (10–14 months (M); n = 20) and old (22–26 months (O); n = 12) C57BL/6 mice. (B) Representative dot plots of CD62L and CD44 expression on FOXP3- CD4 T cells (conventional CD4 T cells) and CD8 T cells recovered from spleen of young, middle-aged and old C57BL/6 mice. (C) Naïve, effector/memory or regulatory of CD4 and CD8 T cell distributions in pooled spleen and lymph nodes from young (n = 20), middle-aged (n = 10) and old (n = 10) C57BL/6 mice. Naïve CD4 T cells were identified as CD45+ TCRβ+ CD4+ FOXP3- CD62L+ CD44low cells, naïve CD8 T cells as CD45+ TCRβ+ CD8α+ CD62L+ CD44- cells, effector/memory CD4 T cells as CD45+ TCRβ+ CD4+ FOXP3- CD62L- CD44high, effector/memory CD8 T cells as CD45+ TCRβ+ CD8α+ non CD62L+CD44- and regulatory CD4 T cells (Treg) as CD45+ TCRβ+ CD4+ FOXP3+. Cumulative results show the mean ± SEM of absolute numbers. P values indicate statistical difference between effector/memory proportion depending on age as followed: ns, non-significant; *, p < 0.05; **, p < 0.01; ***, p < 0.001 (Student’s t test).