Immunological alterations associated with aging (immunosenescence) do not represent a simple unidirectional decline in all functions but develop as a complex remodeling of the immune system, involving multiple reorganization and developmentally regulated changes. In general, most data available about aging were obtained at particular age intervals and most of them come from Caucasian individuals from either Europe or the United States. Here, we report the frequencies of major lymphocyte subsets in healthy Brazilian individuals from 2 distinct geographic regions (Southeast and South) at several age intervals spanning a lifetime period (0–86 years). Overall, we demonstrated that changes in the frequencies of cells related to both innate and adaptive immunity clearly occur with aging in these individuals. These changes were not progressive and equally steady for all cell populations tested but instead showed an oscillatory or rhythmic behavior that was distinctive of each population at different age intervals. We also observed that abrupt changes in the frequencies of immune cells may occur in healthy individuals over 75 years old, suggesting there is an impaired flexibility of the immune system at late stages of life to sustain homeostasis via immune mechanisms. We presented reference ranges for healthy Brazilian individuals at all ages. The knowledge of these parameters in further detail will allow interventions to optimize immune function in advanced age and to improve the quality of life in the elderly.

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