The thymus gland serves a vital role in T-cell production and regulation in the body and in mature immunity. The thymus gland's function is to receive "immature” T -cells that are created within the red bone marrow and teach the immature cells how to become functional, mature T- cells who are used solely to attack foreign cells. The thymus gland plays it's greatest role in childhood, enlarging until puberty where it subsequently begins to shrink at the onset of puberty and into full adulthood. As the thymus shrinks, its tissues are replaced by adipose tissue. According to researchers, the shrinking is due to the reduced role of the thyroid in adulthood – the immune system produces most of its T cells during childhood and requires very few new T cells after puberty. In a healthy adult, the thymus should be residual and continue to shrink throughout maturity.
While not fully understood, research shows a correlation between thymectomy as a surgical treatment for AChR and seronegative patients and an increase in long term stability and remission compared to patients who do not have surgical intervention. Experts do not all agree that thymectomy is an appropriate course of action for patients who present without thymoma (a tumor on the thymus gland that is typically benign but can be malignant in some cases and is seen in an estimated 20% of Myasthenics), however, a new study affirms the belief that thymectomy for non-thymoma patients is beneficial (some criteria excludes certain patient populations).