Fig. (4).

Distribution of CD4+ and CD8+ T-cells into naïve, central memory, effector memory (EM) and effector memory RA (EMRA) cells, and distribution of EM and EMRA cells into subsets defined by CD28 and CD27 expression. (A) Schematic model of the T-cells differentiation subsets with respect to CD45RA and CCR7 expression and dot plots representative of these subsets in young people and elderly subjects. (B) Representative dot plots of the subsets defined by CD27 and CD28 expression for individuals in each group. EM Tcells can be divided into EM1 (CD27+CD28+), EM2 (CD27+CD28^null, only in CD8+ T-cells), EM3 (CD27^nullCD28^null) and EM4 (CD27^nullCD28+). Similarly, EMRA cells can be divided into pE1 (CD27+CD28+) and pE2 (CD27+CD28^null, only in CD8 T-cells) and E (CD27^nullCD28^null) groups.