MUTATION FREQUENCY IN HUMAN BLOOD-CELLS INCREASES WITH AGE

Using either the colony formation assay or flow cytometry, it is feasi ble to measure the frequency of rare mutant lymphocytes or erythrocyte s in human peripheral blood, Accordingly, we have investigated the mut ant cell frequencies of the hypoxanthine-guanine phosphoribosyltransfe rase and T-cell receptor genes in T lymphocytes and of the glycophorin A gene in erythrocytes of several hundred persons aged 0-96 years. Th e mutant frequency of every one of these genes increased significantly with age. A simple accumulation of mutations in hematopoietic stem ce lls over time may explain the age-dependent increase in the frequency of glycophorin A mutants. In contrast, a balance between mutant cell g eneration and loss should be taken into account for the mechanism of t he increase of T-cell mutations.