Age-related changes in the expression of CD95 (APO1/FAS) on blood lymphocytes.

Aging is associated with alterations of the immune system, thought to be related to an increased susceptibility to infectious diseases, and possibly to cancer and autoimmunity in the elderly. In the present paper we report data obtained on freshly collected blood from 148 healthy subjects of different ages (from cord blood to 102 years old). The subjects were divided into seven age classes (cord blood, 3-11 years, 15-39 years, 41-60 years, 61-74 years, 75-84 years, 85-102 years) and their lymphocyte subsets and the expression of the apoptosis-related molecule CD95 were evaluated. In respect of lymphocyte subsets, the major differences were found in the cord-blood samples compared with the oldest old groups. In the cord-blood group, the absolute number of all the lymphocyte subsets was enhanced, but in the oldest group, an increase of CD16+ lymphocytes was observed, whereas CD19+ lymphocytes, which progressively decrease with age, continue to decrease further in the very old. The data show that the expression of CD95 increases until age 74 years, whereas in the oldest old it tends to decrease again. The trend of CD95 expression seems to be related to the change of expression of CD95 on CD4+ lymphocytes, because the CD8+/CD95+ population rose steadily throughout the entire age range. The evaluation of CD95+/CD45R0+ lymphocytes shows similar results to those observed analyzing CD95 on total lymphocytes. Furthermore, a constant increase of CD95+/CD28+ and a related decline of CD28+ lymphocytes was observed in all age groups. These data suggest that the expression of CD95 on the different subsets of lymphocytes can be considered a good marker for studies of immunosenescence, because it may be predictive of successful aging, and can partially explain the change in lymphocytes subsets in elderly.