Age-dependent responsiveness of T lymphocytes to allogeneic and PHA stimulation.

In the course of family investigations a linear age-dependent decrease of reactivity against pooled allogeneic lymphocytes was found between 20 and 70 yr of age. This decreasing tendency was ascertained also by the investigation of unrelated people of a more advanced age. In the elderly, maximal transformation values in PHA stimulation investigated at different PHA doses showed a similar degree of reduction as allogeneic reactivity, and a good correlation between the two parameters of T-lymphocyte function has been found.