Aging and lymphocyte function: a model for testing gerontologic hypotheses of aging in man

Area of Science:

• Immunology
• Gerontology
• Cellular Biology

Background:

• Advanced age is linked to decreased T lymphocyte responsiveness in humans and animal models.
• Age-related T cell decline is not explained by reduced T cell numbers or altered CD4+ to CD8+ ratios.
• A decrease in naive T cells and a corresponding increase in memory T cells are observed with aging.

Purpose of the Study:

• To investigate the hypothesis that thymic involution leads to reduced naive T cell output.
• To explore the role of accumulated memory T cells in age-associated T cell dysfunction.
• To examine if the biological age of memory T cells contributes to impaired in vitro activation responses.

Main Methods:

• Analysis of T cell populations (naive vs. memory) in aging humans and animal models.
• Assessment of in vitro T cell responsiveness and activation.
• Investigation of cellular aging mechanisms within memory T cell subsets.

Main Results:

• A decline in naive T cells and a rise in memory T cells with increasing age.
• Evidence suggesting that the biological age of accumulated memory T cells correlates with reduced activation responses.
• Identification of a subset of memory T cells becoming refractory to activation due to in vivo aging.

Conclusions:

• Thymic involution and lifelong antigen exposure contribute to an altered T cell repertoire with age.
• The accumulation of biologically aged memory T cells is a key factor in age-related T cell functional decline.
• Memory T cells offer a valuable model for studying the mechanisms of in vivo cellular aging.