CHANGES IN LYMPHOCYTE SUBSETS, INTERLEUKIN-2, AND SOLUBLE INTERLEUKIN-2 RECEPTOR IN OLD AND VERY OLD-AGE

In this study, the changes in some of the cellular components of the i mmune system and the activity of the cytokine interleukin 2, important for immune activation and lymphocyte proliferation, were measured in a large cross-sectional study of all age groups including octogenarian and nonagenarian subjects. In 206 apparently well community-living su bjects, the absolute lymphocyte count and T and B cell numbers fell a little in old and very old subjects. Within the T cell compartment, he lper/inducer CD4+ T cells, together with their subsets identified as ' naive' (CD4+/CD45RA+) and 'memory' (CD4+/CD45RO+) cells, also showed a decline with increased age, The suppressor/cytotoxic CD8+ subset show ed no age-related change. The levels of the cytokine interleukin 2 wer e very low in octogenarian and nonagenarian subjects, while the solubl e interleukin 2 receptor levels increased with increasing age. The int erleukin 2 levels were associated with number and percentage of the 'm emory' (CD4+/CD45RO+) subset of T cells which mediates the host respon se to previously met antigens, Since the interleukin 2 values were ver y low in the oldest groups and were associated with a reduced 'memory' (CD4+/CD45RO+) compartment, this suggests a possible mechanism of why the very elderly subject is more susceptible to morbidity and mortali ty from infectious or other agents.