The thymus is a small, butterfly-shaped organ located in the upper chest just above the heart. It plays a critical role in the production and “education” of T cells, a type of white blood cell essential for immune system functioning. The thymus gland is the organ where precursor cells from the bone marrow mature into functional T cells, capable of distinguishing between the body’s own cells and foreign invaders, a critical function of a healthy immune system.

However, as humans age, the thymus undergoes a process known as thymic regression or involution resulting in a decline in thymic function. This contributes to age related increased vulnerability to infections, autoimmune diseases, and cancer.

Thymic involution refers to the gradual shrinking and loss of functional tissue within the thymus, starting as early as puberty. These changes are ushered in by age related hormonal changes in growth hormone and sex hormones, by free radicals and inflammation and by age related reduction in stem cells. By mid-life much of the thymic tissue is replaced by fatty tissue, significantly reducing its ability to produce new T cells, one of the main immune cells to fight foreign invaders.

This reduction and its effects on the immune system is so important it has been termed immunosenescence by the medical community. Immunosenescence is known to contribute to the increased susceptibility of older adults to infections, including respiratory viruses like influenza and, more recently, SARS-CoV-2. It also contributes to increased autoimmunity with increased susceptibility to illnesses such as rheumatoid arthritis, lupus and other autoimmune illness. Lastly, the decline in thymic function contributes to an increased risk of cancer. T cells play a crucial role in identifying and eliminating cells that have become cancerous. It’s clearly important to try to maintain thymic function to maintain a healthy immune system.

Fortunately, there are nutritional and lifestyle interventions that may help slow the loss of thymic tissue and scientific articles now show there are innovative ways to restore thymic tissue.