Changes in lymphocyte subsets and immune competence in very advanced age.

To study the changes in immune system during aging and their effects on patient survival, immune functions of 18 very old (92-107 years) hospital patients were tested. After three years follow-up, the survival of patients and the correlation of immune capacity to lifetime were determined. In the very old patients, the frequency of T lymphocytes was significantly lower than in young adults. This decrease was attributed more to the CD8-positive than to CD4-positive cell subset, leading to generally high CD4/CD8 ratios. The mitogenic responses to phytohemagglutinin (PHA) and concanavalin A (Con A), but not pokeweed mitogen (PWM), were decreased significantly in cultures with isolated lymphocytes, while in whole blood cultures the responses to PHA and PWM but not to Con A were reduced. In very advanced age, there was a significant decrease in the number of B cells, and the ability to produce IgM in vitro was decreased. During the follow-up time, 15 out of the 18 patients died. However, their lifetime was not in correlation with any single immune parameter.