[Age and the response of peripheral blood lymphocytes to mitogens].

Reactions of the peripheral blood lymphocytes of normal persons from 19 to 49 years of age to the following mitogens was studied; phytohemagglutinin (PHA), concanavalin A (ConA), rabbit serum against human thymocytes (ATS). A significant reduction of the lymphocytes proliferative response to ConA was reported in persons above 30 years old. There was also demonstrated a significant negative correlation between the proliferative response indices and the donor's age (in ConA-stimulation-for the whole group examined, and in ATS-stimulation-for persons aged from 30 to 49 years only. Analysis of the intensity of thymidine-(3)H incorporation showed that with the advance of age there was a fall of the percentage of cells with an intensively labelled nuclei and an accumulation of cells with weakly labeled nuclei, this phenomenon was observed both when the proliferative response was decreased and when no significant differences were reported in these indices.