What is the role of the thymus in T cell development?
T cell development occurs in the thymus; the thymic microenvironment directs differentiation as well as positive and negative selection. In the thymus, T cells develop their specific T cell markers, including TCR, CD3, CD4 or CD8, and CD2. T cells also undergo thymic education through positive and negative selection.
What is the action of thymic hormones on T lymphocytes T cells?
Thymic hormones serve a major role in preserving the functions of the immune system, and cytokines have essential roles in the control of immune responses. Cytokines are small polypeptides that regulate cell function and are predominantly secreted by immune cells.
How is an enlarged thymus treated?
Myasthenia gravis can be treated by removing the thymus (whether or not a thymoma is present) or with medicines that either strengthen the chemical signals to muscles or weaken the immune attack on the muscles.
Why is thymus enlarged?
Thymic hyperplasia is seen in a number of immunologic states including Graves disease, collagen vascular disorders, and, most commonly, myasthenia gravis, where it occurs in about 75% of cases. This greatly enlarged thymus was removed from a patient with myasthenia gravis.
Can thymus be seen on xray?
Conventional Radiography The thymus usually has smooth borders and remains visible on radiographs through the age of 3 years. The thymic wave sign, a scalloped or wavy contour of the organ, is created by the impression of the anterior reflection of the ribs (Fig 6).
Are Thymomas always malignant?
However, thymoma is now considered to be always possibility malignant and the best way to determine if the condition will recur after treatment is to examine if the tumors have spread to other areas. See also emphysema, mediastinal tumors, mesothelioma and sarcoidosis for other lung diseases.
How rare is a thymoma?
Most tumors that begin in the thymus are thymoma, but overall, thymoma is uncommon. There are only 1.5 cases of thymoma per every 1 million people that occur each year in the United States. This means about 400 people per year develop thymoma.