Interleukin-2 and aging: decreased interleukin-2 production in healthy older people does not correlate with reduced helper cell numbers or antibody response to influenza vaccine and is not corrected in vitro by thymosin alpha 1.

The capacity of lymphocytes obtained from healthy young or old volunteers to produce interleukin-2 was measured and the results were compared with other measures of immune function. The in vitro effect of thymosin alpha 1 on interleukin-2 production was also measured. Interleukin-2 was lower in lymphocytes from the elderly, and individuals with low production also had lower proliferative responses in vitro to phytohemagglutinin. These individuals did not have a reduced helper T-cell number, abnormal ratio of helper to suppressor T-cells or reduced antibody production in response to vaccine. Thymosin alpha 1 did not have a consistent effect on interleukin-2 production.