In healthy humans, phenotypic restructuring occurs with age within the CD3+ T-lymphocyte complement. This is characterized by a nonlinear decrease of the percentage of “naïve” (CD45RA+) cells and a corresponding nonlinear increase of the percentage of “memory” (CD45R0+) cells among both the CD4+ and CD8+ T-cell subsets. This is illustrated in the two-part figure below and on the next page.

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