Mitogenic activity of 12-O-tetradecanoyl phorbol-13-acetate on peripheral blood lymphocytes from young and aged adults.

The effect of age on the proliferative response to 12-O-tetradecanoyl phorbol-13-acetate (TPA) was examined using peripheral blood lymphocytes from 185 adults. TPA-induced DNA synthesis measured by cellular 3H-thymidine incorporation was found, like the responses of cells activated by PHA and Con A, to markedly diminish with advancing age. The presence of indomethacin (1 microgram/ml) or Ro 20-5720 (10 micrograms/ml) in TPA activated cell cultures, unlike PHA stimulated cultures, did not result in augmentation of 3H-thymidine incorporation by cells from elderly individuals. These results demonstrate that prostaglandin synthesizing suppressor cells are not responsible for the age-related depression of cellular immune function observed in TPA activated cells and confirm the observation that decreased production and/or utilization of soluble mediators, such as IL-2, may account for the diminished mitogen responsiveness of lymphocytes from elderly individuals.