Age- and sex-related changes of the lymphocyte subsets in healthy individuals: an analysis by two-dimensional flow cytometry.

The relative and absolute numbers of the peripheral blood lymphocyte (PBL) subpopulations from 156 healthy men and women of different ages (20-99 years old) were studied by the use of monoclonal antibodies (MoAbs) and two-dimensional flow cytometry. The percentage of pan-T MoAb-positive cells decreased with age, which was attributable to a relative decline in the CD8+ suppressor/cytotoxic T cells, more precisely in the CD8+ CD11- cytotoxic T cells. Those of CD4+ Leu-8- helper T cells, CD3+ HLA-DR+-activated T cells, and natural killer subsets (Leu-7+, CD16+, Leu-7+ CD16+ or Leu-7+ CD16-) increased with age. The absolute numbers of most of the lymphocyte subsets examined declined with age except that those of natural killer cell subsets and helper T cells remained unchanged. It should be noted that the PBL subsets differed markedly according to age and sex, the changes being more evident among women.