The aim of the study was to investigate whether normal aging leads to blood cells being produced from fewer cell clones. This was examined by comparing which X chromosome the cells were using between different age groups and between neutrophils and T cells. In other words, they studied human hematopoiesis acros s age by analyzing purified blood cell lineages from the subjects. --- 👋 ------- ## Study - 197 hematologically normal females - 23 newborn - taken during delivery - 94 young adult - age: 17-50 median 30 - 80 eldery - age: 75-96 median 81 - purified neutrofils - purified T-cells ---- ### Methods 1. Peripheral blood samples were collected 2. Neutrophils and T cells were isolated using cell separation techniques _(centrifugation followed by lineage-specific purification)_ 3. X-chromosome inactivation was analyzed using the HUMARA PCR assay _(PCR-based measurement of which X chromosome is active)_ 4. T cells were analyzed by PCR to check for clonal expansion _(T-cell receptor γ gene rearrangement analysis)_