The thymus gland lies in the upper chest area beneath the sternum or breastbone , plays an important role in the development of the immune system in early life. Its cells form a part of the body’s normal immune system. The gland is somewhat large in infants, grows gradually until puberty, and then gets smaller and is replaced by fat with age.
Thymus is involved in immune system development.
Hematopoietic precursors from the bone-marrow, referred to as thymocytes, mature into T-cells. Once mature, T-cells emigrate from the thymus and constitute the peripheral T-cells.
The stock of T-lymphocytes is built up in early life, so the function of the thymus is diminished in adults. It is largely degenerated in elderly adults and is barely identifiable, consisting mostly of fatty tissue, but it continues to function as an endocrine gland important in stimulating the immune system.
Abnormalities of Thymus
Any congenital defect in thymic genesis or a defect in thymocyte development can lead to a profound T cell primary immunodeficiencis like Severe Combined Immunodeficiency Syndrome, DiGeorge Syndrome .
Abnormalities of thymus are also found in autoimmune diseases like myasthenia gravis.