Caloric restriction and weight management (obesity accelerates involution) preserve the thymus in mice; chronic aerobic exercise maintains young T cells in older humans.
Lower T-cell diversity compromises tumor surveillance with age.
Defective thymic selection contributes to the loss of immune tolerance with age.
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Thymic involution is the process by which the thymus shrinks with age and produces fewer T cells, impairing immunity and increasing the risk of infection in older adults; in addition, thymic involution increases the risk of cancer and autoimmunity with age because it reduces the diversity of T cells, which are the conductors of the immune system responsible for coordinating responses against pathogens, tumors, and dysfunctional self cells that could become autoimmune problems.
The thymus is a lymphoid organ located behind the sternum and near the heart; its main purpose is to produce mature T cells, a type of white blood cell involved in allergies, autoimmunity, and immunity against pathogens; T cell production falls sharply after adolescence, followed by a marked increase in the rate of thymic involution after age 40, which means that from that age on the immune system becomes less and less able to respond effectively to new pathogens.
Research has identified some mechanisms and possible strategies to improve immunity: caloric restriction through activation of PPAR-gamma reduced the rate of thymic involution in mice and increased the number and diversity of circulating T cells; maintaining a healthy weight may slow thymic involution, since diet-induced obesity increased immunosenescence and thymic involution in mice; and stress raises glucocorticoids that induce cell death in thymic cells, suggesting that stress-reduction tools may slow involution.
A study of 125 amateur cyclists and 75 sedentary adults aged 55-80 found that the older cyclists had the same number of young T cells as young adults aged 20-36; the older cyclists showed no increase in senescent immune cells compared with the young, and had markedly lower levels of proinflammatory IL-6 and higher levels of IL-7, which slows thymic shrinkage, suggesting that intense exercise in older adults may significantly slow thymic involution and maintain more youthful immunity.
Information, not medical advice. Scientific evidence reflects the quality of the studies.