Figure 1. The effect of age on lymphocytes. Lymphocyte subpopulations and T cell senescence were assessed by flow cytometry (n=51 donors). (A) The proportion of T cells (CD3+) gradually increases and NK cells (CD3-/CD56+) and B cells (CD3-/CD56-) have a decreasing trend with age (Jonckheere test). (B) Among CD4 cells, CD28- cells accumulate in old individuals, while there is a partial reduction in the very old (quadratic effect **). (C) A small proportion of CD28- cells expresses CD56, but some differences are found with age. (D) CD28 loss is more pronounced in CD8 cells and a gradual accumulation with age was found (Jonckheere test ***). (E) The gain of CD56 is also more pronounced in CD8 cells and increased proportions were found with age. Age range in years.