Hi there!

T-lymphocytes are a type of white blood cell that play an important role in your immune system, which helps your body fight disease and infection. The thymus gland is responsible for the maturation of T-lymphocytes. However, as you mentioned, the function of the thymus gland gradually declines with age, which can lead to a decrease in the number of T-cells in the body.

When T lymphocytes are damaged by harmful bacteria and new T lymphocytes are not maturing or maturing slowly, the body relies on other components of the immune system to fight infections. 

For example, B-lymphocytes produce antibodies that can neutralise harmful bacteria and viruses. Additionally, natural killer cells can recognise and destroy infected cells of the body.

When adults have low functioning thymus gland, the body tries to compensate by increasing the production of T-lymphocytes in other organs such as the spleen and lymph nodes. However, the rate of T-cell death and maturation is not always perfectly matched, which can lead to a decrease in the number of T-cells in the body. This can make it more difficult for the body to fight infections, especially in older adults.

Thanks