NUMERICAL AND FUNCTIONAL-CHARACTERISTICS OF LYMPHOCYTE SUBSETS IN CENTENARIANS

The immune system in the aged is a very interesting subject for study. In this study, analysis was extended to extrathymic T cells as well a s NK cells and ''conventional'' T cells (i.e., thymus-derived T cells) in terms of their constitution and function in both healthy and unhea lthy centenarians. Middle-aged persons were used as controls. Healthy and unhealthy centenarians showed lower levels in the proportion and a bsolute number of lymphocytes. The major change in the constitution of lymphocyte subsets was increased levels in the proportion of NK cells (CD56(+)/CD57(+)) and extrathymic T cells (CD3(+)CD57(+)). Inversely, conventional T cells decreased in proportion and function (i.e., prol iferative response to mitogen). Although NK cells increased in centena rians, NK activity by whole lymphocytes and the purified NK fraction d ecreased. The difference between healthy and unhealthy centenarians wa s small in all parameters, the only difference being a lower level of expression of CD56 antigens on CD57(+) T cells in unhealthy centenaria ns. These results indicate that there is a major shift in lymphcyte po pulation from conventional T cells to NK cells and extrathymic T cells with aging. Concerning the age-associated increases in CD56(+) T and CD57(+) T cells, these cells correspond to NK1(+) T cells in mice.