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The effects of aging on the activation of the cytoplasmic tyrosine protein kinase p56(lck) have been investigated in PBL from adult and elderly subjects upon activation with mitogens or different co-stimuli. Results show that the amount and phosphorylation of p56(lck) are reduced in PBL from elderly as compared to adult subjects. This finding suggests that alterations in p56(lck) may contribute to the age-associated loss of some T cell functions, such as proliferation and IL-2 production, which are found decreased in PBL from old individuals. However, p56(lck) seems irrelevant to the production of IFN-gamma and IL-4 which were both found increased in the PBL from old subjects, as expected from the relative expansion of memory versus naive T cell subpopulations in aging.

Previous studies on DNA repair in ageing have demonstrated increased frequencies of single and double strand breaks in lymphocytes from elderly subjects and, as a consequence, decreased efficiency in DNA replication. We have investigated the relationship between cell proliferation and the nuclear expression of ku protein in a human population of 43 subjects of different ages. Ku is an heterodimeric protein composed of two subunits of 70 and 80 kDa, which is involved in the early steps of DNA damage recognition. In the present study, PBL from subjects of different ages were PHA-activated to evaluate the stimulation index and the production of Th1- and Th2-type cytokines. Moreover, nuclear extracts were obtained from activated lymphocytes to evaluate by a gel retardation assay the presence and the functional activity of the heterodimer ku 70/80. Our results indicate that ageing affects the mitotic responsiveness and cytokine production to a significant extent, but only marginally the expression of ku 70/80. These findings suggest that the age-related impairment in DNA repair mechanisms are only in part related to the reduced expression of ku protein able to recognize DNA damage.

Lymphocyte activities were determined in a population of 26 institutionalized aged subjects, selected as healthy according to the SENIEUR protocol and previously reported to display immunological and endocrinological abnormalities correlated with depressive disorders. The lymphocyte mitotic response to PHA, which was reduced in aged as compared to adult subjects, was found to be significantly lower and negatively correlated with the depression score in the elderly subjects. In supernatants of PHA-stimulated lymphocyte culture from aged subjects, IL-2, IL-4 and gamma-IFN levels were very low and more severely affected in the depressed aged group. Each cytokine production was negatively correlated with age and depression score. NK activity was lower in the aged and it could be augmented by the addition of IL-2 or alpha-IFN, even though to a lesser extent than in the adult subjects. The nondepressed aged displayed higher levels of IL-2 inducible NK activity than the depressed aged subjects. IL-2 and alpha-IFN stimulated NK activities were negatively correlated with depression score. The present work indicates that the psychological status could affect lymphocyte reactivity in the aged. Given the relatively high frequency of affective disorders in these subjects, the psychological status should be considered in studies of immune senescence.

Twenty-six institutionalized elderly subjects, selected as healthy according to the SENIEUR protocol, were compared to adult controls to establish correlations between affective disorders and immune abnormalities and to investigate underlying neuroendocrine mechanisms. After an extensive psychodiagnostic examination, 35% of the aged subjects were classified as depressed. Cutaneous delayed hypersensitivity tests showed reduced responses in the aged, but no correlation was found with the psychological status. Examination of the peripheral blood lymphocyte subsets revealed no imbalance in the percentages of CD3+, CD4+, CD8+ cells in the aged. A slight reduction in the CD4+/CD8+ cell ratio could however be detected in the non-depressed aged, as compared to adult controls. The CD4+/CD45R+ cell subset was reduced in non-depressed aged. The percentage of B lymphocytes was reduced in the aged, mostly in the non-depressed subjects. No changes were detected in the percent of OKDR+ cells. The percentage of CD16+ cells was found unchanged, while that of Leu7+ cells was significantly higher in the aged than in the adults and in the non-depressed than in the depressed aged. Leu7+ cell levels were negatively correlated with the depression score. On double labelling, the percent of CD16+/Leu7+ cells appears increased in the subgroup of depressed aged and positively correlated with age. Plasmatic and urinary cortisol levels were both positively correlated with depression score. Urinary cortisol level was higher in the depressed aged. These parameters, as well as plasmatic ACTH, beta-endorphin and urinary catecholamines, were not correlated with immune responses. Based on these findings, we recommend that the neuroendocrinological conditions should be taken into account when healthy subjects are examined in studies of immune senescence.