Fig. 5
From: Effect of age and sex on immune checkpoint expression and kinetics in human T cells
PD-1 expression frequencies among CD4+ differentiation subsets of young and older adults. Age effects on PD-1 expression were determined by flow cytometric staining of whole blood according to the Miyara classification employing CD45RA and CD25 [21, 22]. By staining for CD45RA and CD25 expression, the following seven fractions were distinguished: Memory CD25- (fraction 5), Memory CD25dim (fraction 4), Memory CD25int Treg (fraction 3), Memory CD25high Treg (fraction 2), Naive CD25- (fraction 6), CD25dim (fraction 7) and Naive CD25int Treg (fraction 1). Graphs represent percentages of PD-1+ cells within the seven different naive and memory conventional and regulatory CD4+ fractions. Dashed line divides conventional memory and naive fractions from regulatory fractions. Open and closed circles respectively represent males and females. Horizontal bars reflect median percentages. Open and closed triangles represent males (n = 2) and females (n = 2), respectively, that were 65 years of age or younger in the OA group. The Mann-Whitney U test was used for comparison between young (YA, n = 20) and older (OA, n = 20) adults. P-values are indicated in the graphs