What theory suggests that a decline in immune system functions contributes to aging?

The immunological theory posits that aging is significantly influenced by the decline in immune system functions. According to this theory, as individuals age, their immune response becomes less effective, leading to an increased susceptibility to infections, diseases, and other health complications. This decline is thought to result from various factors including decreased production of immune cells, alterations in the function of existing immune cells, and a decline in the body's ability to respond to new antigens. This weakening of the immune system can accelerate the aging process and contribute to the overall decline in health status in older adults, thereby linking immune function directly to aging.

In contrast, the other theories—oxidative stress theory, cellular aging theory, and programmed aging theory—focus on different mechanisms of aging. The oxidative stress theory explores the damaging effects of free radicals on cellular structures, while cellular aging theory examines the process of cellular senescence. The programmed aging theory suggests that aging is a genetically programmed process, distinct from the immune decline perspective. Each theory adds to the understanding of aging but does not specifically emphasize the role of the immune system in the way that the immunological theory does.