Daan Pieren

46 Chapter 2 % of max PD-1 Th cells Day 0 Day 2 Young Aged Tc cells Young Aged Young Aged Th cells Tc cells CD25 + CD69 + PD-1 + cells CD25 + CD69 + PD-1 - cells A B C Day 0 Day 2 0 20 40 60 80 100 % CD25 + CD69 + of PD-1 + Tc cells *** Day 0 Day 2 0 20 40 60 80 100 % CD25 + CD69 + of PD-1 - Tc cells ** Day 0 Day 2 0 20 40 60 80 100 % CD25 + CD69 + of PD-1 + Th cells *** Day 0 Day 2 0 20 40 60 80 100 % CD25 + CD69 + of PD-1 - Th cells *** Young (2 months) Aged (28 months) Day 0 Day 2 Day 0 Day 2 0 20 40 60 80 100 PD-1 + Th cells (%) p = 0.06 ** Day 0 Day 2 Day 0 Day 2 0 20 40 60 80 100 PD-1 + Tc cells (%) *** ns Figure 7. PD-1 + Th and Tc populations contain less activated cells at old age. ( A ) Histograms depict expression of PD-1 by Th and Tc cells of young (n=6, 2 months old) and aged (n=4, 28 months old) mice at day 0 and at day 2 after culturing with an intermediate stimulatory strength. ( B ) Graphs show the induction of PD-1 + Th and Tc cells of young and aged mice after stimulation (day 2). ( C ) The activation status of PD-1 + and PD-1 - Th and Tc cells from young and aged mice was analyzed before and after stimulation. The proportion of activated cells was characterized by the simultaneous expression of CD25 and CD69. Mean ± SD; ** p < 0.01, *** p < 0.001 for difference between young and aged mice using Kruskal-Wallis test.