Thymus

The thymus is a lobular endocrine gland positioned in the chest. It lies between the two lungs, behind the sternum (breastbone), on the ventral (front) side of the aorta.

Role in the immune system

The thymus is important chiefly for the development of the immune system. It secretes a group of peptide hormones called thymosins.

Thymosins act on the body's defence mechanisms in two ways:

• They drive the differentiation of T-lymphocytes, the white blood cells responsible for cell-mediated immunity.
• They also promote the production of antibodies, which provide humoral immunity.

Change with age …