Thymus removal surgery (thymectomy), a therapeutic alternative for myasthenia gravis (MG), appears to have long-lasting consequences for immune system function, according to a recently published study in the Journal of Cardiothoracic Surgery.
About the thymus and MG
The thymus is an important immune organ that plays a key role in the development and maturation of T cells (also called T lymphocytes), a type of white blood cell. The thymus also has a crucial role in self-tolerance, the process by which lymphocytes learn not to attack the body’s own cells.
Research shows that up to 80% of patients with MG exhibit some form of thymic abnormality that alters the self-tolerance process. Therefore, thymectomy has emerged as a common and effective therapeutic option for MG. However, recent evidence suggests that patients who undergo thymectomy are at a higher risk of infection and cancer.
In light of these findings, the study’s authors aimed to further analyze the immune changes that occur after thymectomy at the cellular level by examining samples from patients with MG who underwent thymectomy and comparing them with samples from MG patients who chose pharmacological treatment.
Learn more about MG signs and symptoms
Thymectomy leads to decreased T cell levels
There are two main kinds of T cells: TCD4 (T helper) and TCD8 (cytotoxic) lymphocytes. The study’s results showed that patients who underwent thymectomy experienced a significant decrease in levels of both TCD4 and TCD8 one month after surgery, compared to patients who began medical treatment. These changes persisted throughout the duration of the study.
The change particularly affected TCD4 lymphocytes: post-op patients presented with abnormally low CD4-to-CD8 ratios.
Thymectomy and medication have similar effects on cytokine and antibody levels
T helper cells produce substances called cytokines that activate other immune cells during an immune response and play a key role in the defense against viruses, cancer and certain bacteria.
The authors observed a significant decrease in cytokines such as interferon gamma, interleukin (IL)-6, IL-2, IL-4, and tumor necrosis factor alpha (TNF-α) in both the surgical and pharmacological treatment groups. However, after 12 months, cytokine levels stabilized in both groups.
There were no significant changes in antibody levels between the two groups, with all patients maintaining stable levels before and after treatment.
Significance of the findings
The results showed that thymectomy represents a significant shock to the immune system. It appears to alter T cell expression over a long period and causes transient alterations in key cytokines essential for immune function.
“While thymectomy can improve MG symptoms, it may also lead to immune alterations. Close monitoring of immune function and infection risk is recommended for MG patients following thymectomy,” the study’s authors concluded.
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