| thymus gland | A bilaterally symmetric lymphoid organ situated in the anterior superior mediastinum. Each of its two lobes consists of an outer zone, the cortex, relatively rich in lymphocytes (thymocytes), and an inner zone, the medulla, relatively rich in epithelial cells. The thymus is the site of the production of T-lymphocytes. The thymus reaches its maximal development at about puberty and then undergoes a gradual process of involution resulting in a slow decline of immune function throughout adulthood. (12 Dec 1998) |
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| thymus hormones | Humoral factors secreted by the thymus gland. They participate in the development of the lymphoid system and the maturation of the cellular immune response. (12 Dec 1998) |
| thymus hyperplasia | Enlargement of the thymus. A condition described in the late 1940's and 1950's as pathological thymic hypertrophy was status thymolymphaticus and was treated with radiotherapy. Unnecessary removal of the thymus was also practiced. It later became apparent that the thymus undergoes normal physiological hypertrophy, reaching a maximum at puberty and involuting thereafter. The concept of status thymolymphaticus has been abandoned. Thymus hyperplasia is present in two thirds of all patients with myasthenia gravis. (12 Dec 1998) |
| thymus-independent antigen | An antigen that does not require T helper cell activation in order for the host's B-cells to be stimulated. Repeating polymers such as polysaccharides are examples of T-independent antigens. (05 Mar 2000) |
| thymus treatment | Treatment of disease by administration of extracts of thymus gland. (05 Mar 2000) |