Figure 6. Identification of “sub-healthy individuals” with PD-1 expression in PBMCs. (A) Proportion of CD3+PD-1+ cells was <4% in the PBMCs of healthy individuals. PBMCs of 95 individuals (aged >50 years) were analyzed, of which 16.84% of samples had a proportion of CD3+PD-1+ cells >4%. (B) Proportion of CD3+CD4+PD-1+ cells was <10% in the CD3+CD4+ T cells of healthy individuals. In these 95 individuals, 9.47% of samples had a proportion of CD3+CD4+PD-1+ cells >10%. (C) Proportion of CD3+CD8+PD-1+ cells was <10% in the CD3+CD8+ T cells of healthy individuals. In these 95 individuals, 37.9% of samples had a proportion of CD3+CD8+PD-1+ cells >10%. We defined CD3+PD-1+ cells/PBMCs >4% and CD3+CD8+PD-1+ cells/CD3+CD8+ cell >10% as “sub-healthy individuals” (4.21%).