Components of the Immune System: Thymus

A previous article entitled, “Components of the Immune System” touched briefly on each part of the immune system and their functions. This article will discuss the functions of the thymus in greater detail and what complications can occur if these functions are not carried out properly.

The Thymus is an organ located in the upper anterior portion of the chest cavity just behind the sternum. The main function of the thymus is to provide an area for T cell maturation, and is vital in protecting against autoimmunity.

The thymus is unique because it reaches its largest stage during childhood and nearly disappears in adults. At birth, the thymus is five centimeters long and is a grey/pink color. It continues to grow until puberty when it can weigh up to 37 grams. When puberty hits, the thymus becomes inactive and with age it starts to shrink. By the age of 75, the thymus only weighs about six grams and is a yellow color.

Although the thymus becomes nearly invisible in adults, it is still important in immune stimulation. Involution of the gland has been linked to loss of immune function in the elderly, susceptibility to infection, and to cancer. As for young children, premature removal of the thymus due to genetic disorders or surgical removal can result in severe immunodeficiency and a high susceptibility to infection.

Another complication involved with the thymus is the potential for cancerous tumors on the gland known as Thymomas. Some Thymomas grow very slowly and are not highly dangerous, but others spread quickly and affect surrounding tissues. Treatment of Thymomas usually involves removal of the entire Thymus.