Age-dependent changes of human blood lymphocyte subpopulations

T- and B-lymphocyte populations were enumerated at four stages of life: at the newly born, infant, adult and aged stages. The proportion of T cells detected by E rosettes and an anti-human T-lymphocyte antigen (HTLA) serum incresed from new-born children to adults, then decreased with ageing. The antiserum detected less mature T cells in aged people. The percentages of cell forming 'active' E rosettes increased with ageing. Lower numbers of B cells bearing surface immunoglobulins were found in adults.Complement receptor-bearing lymphocytes (percentages and absolute numbers) decreased from new-born children to aged humans. Finally, the number of monocytes were significantly greater in the young than in adult and aged people. Such results bring new data concerning the age-dependent changes of lymphocyte subpopulations and concerning the significance of various techniques used together to detect mononuclear cell populations in the human peripheral blood.