Thymus Therapy is the most important building block for immune therapy. This initial therapy involves a series of thymus extract injections, which activate and balance the body’s immune system. The thymus gland is located just behind the sternum on top of the heart. This gland is the center of our immune system. The function of the thymus is to produce and “educate” T-lymphocytes (T cells). These cells are critical to the adaptive immune system. The thymus changes its size and function during our life cycle. It is largest and most active in newborns, infants and in the years prior to adolescence. By the early teens, the thymus begins to shrink and thymus tissue is replaced by fatty tissue.