Immunosenescence: Aging and Immune System Decline

Abstract

Immunosenescence, a systematic reduction in the immune system connected with age, profoundly affects the health and well-being of elderly individuals. This review outlines the hallmark features of immunosenescence, including thymic involution, inflammaging, cellular metabolic adaptations, and hematopoietic changes, and their impact on immune cells such as macrophages, neutrophils, T cells, dendritic cells, B cells, and natural killer (NK) cells. Thymic involution impairs the immune system's capacity to react to novel antigens by reducing thymopoiesis and shifting toward memory T cells. Inflammaging, characterized by chronic systemic inflammation, further impairs immune function. Cellular metabolic adaptations and hematopoietic changes alter immune cell function, contributing to a diminished immune response. Developing ways to reduce immunosenescence and enhance immunological function in the elderly population requires an understanding of these mechanisms.

Keywords: cytokines; immune system; immunoscenence; inflammation; thymus.

Figure 1

Hallmarks of immunosenescence. The primary characteristics of immunosenescence, including thymic involution, inflammaging, cellular metabolic adaptation, and hematopoietic changes. Each section highlights the physiological and molecular changes that contribute to reduced immune competence and an increased inflammatory response with aging. Arrows indicate the direction of change: ↑ denotes an increase and ↓ denotes a decrease.

Figure 2

Impact of Aging on Immune Cells. The effects of aging on various immune cell types, including dendritic cells, macrophages, T cells, B cells, natural killer cells, and neutrophils. Key changes involve reduced cell numbers, altered expression markers, decreased proliferation, telomere dysfunction, and increased reactive oxygen species (ROS), indicating a decline in immune function with age.

Figure 3

Approaches for managing age-related immune decline. Vaccination, p53 modulation, a Mediterranean diet, exercise, gut microbiome support, and supplements are promising strategies to combat immunological aging. They aim to lower inflammation and strengthen older people’s immune systems.

Figure 4

Comparative overview of young and aged immune systems. Key differences between young and aged immune systems. Young immune systems feature high thymopoiesis, naive T cell production, diverse T and B cells, and robust innate immunity. In contrast, aged immune systems exhibit thymic involution, memory cell dominance, impaired innate immunity, and increased inflammation.