Aging profoundly impacts the immune system through two interconnected, mutually reinforcing processes: immunosenescence and inflammaging.

1. Immunosenescence (Immune Decline) Immunosenescence refers to the gradual deterioration of both the innate and adaptive immune systems. A key hallmark is "thymic involution" (the shrinking of the thymus), which drastically reduces the body's output of new, naïve T cells required to recognize and fight novel pathogens. Concurrently, there is an accumulation of exhausted, late-stage memory lymphocytes, frequently driven by a lifetime of chronic antigenic stress from latent infections like Cytomegalovirus (CMV). Innate immune cells, such as macrophages and neutrophils, also exhibit reduced pathogen-clearing and chemotactic abilities. Consequently, older adults experience increased susceptibility to infecti ...