Immunologic Markers in a Longitudinal Study of Aging in Pigtailed Macaques (Macaca nemestrina)

Blood lymphocyte subsets, serum immunoglobulins (Ig), response of lymphocytes to mitogens, and natural killer (NK) cell activity were evaluated as potential biomarkers for primate aging. All were evaluated in a cross-sectional study of 60 pigtailed macaques (Macaca nemestrina) ranging from 2 to 32 years of age. Lymphocyte responses to mitogens were lower in older animals than in most younger ones. NK cell activity showed no clear relation to age cohort. In a longitudinal study of lymphocyte subsets and immunoglobulins, class I restricted T cells (CD8+bri) of the memory (CD18+M) subtype increased with age, whereas those of the naive (CD18+du") subtype decreased with age in females. A class II restricted T-cell subset (CD4+CD45RA~), which includes memory T cells, increased with age in females. Serum IgA increased. These results support the utility of memory and naive subsets ofCD8+ T cells, CD4+ T cells, and serum IgA as biomarkers for longitudinal studies. Total lymphocytes, total T cells, CD4+ T cells, and CD8+ T cells may also be useful in this species. STUDIES in rodents suggest that the rate of aging may beslowed and the natural life span extended by dietary intervention (Schneider and Reed, 1985). Such an observa-tion underscores the need for means of assessing potential life span-extending interventions in long-lived species (Schneider and Reed, 1985; Ingram et al., 1990). Th