Age-associated changes of memory (CD45RO+) and naive (CD45R+) T cells

1. The total number of lymphocytes and the percentage of CD45RO+ (putative memory T cell) and CD45R+ (putative naive T cell) were determined in 15 cord blood samples, 66 healthy children ranging in age from 1 to 18 years, 16 adults (23-59 years) and 16 aged individuals (60-96 years). 2. The total number of lymphocytes decreased with age and reached the adult range in children aged 11-14 years. CD45R+ T cells were the predominant cell type in cord blood and decreased with age up to the adult group, while the percentage of CD45RO+ T cells was low in cord blood and increased with age. No significant difference was observed between the adult and the aged groups for either lymphocyte subset. 3. These data support the view that CD45RO+ and CD45R+ T-cell subsets represent maturational stages of T cells.