Beta-2 microglobulin (β2-microglobulin or B2M) is a small protein that is present on the surface of most nucleated cells in the body, including lymphocytes (a type of white blood cell). It’s a component of the major histocompatibility complex (MHC) class I molecules, which are important for the immune system’s ability to recognize foreign substances.
Here are some key points about beta-2 microglobulin:
- Role in the Immune System: Beta-2 microglobulin associates with the alpha chain of MHC class I molecules. These molecules display peptide fragments from within the cell on the cell’s surface, allowing the immune system to monitor cellular health. If a cell is infected by a virus or is cancerous, these MHC class I molecules present pieces of these abnormal proteins, alerting the immune system.
- Use in Medical Diagnosis: The level of beta-2 microglobulin can be measured in the blood. Elevated levels can be found in some disorders, especially those affecting the immune system or kidneys.
- Association with Kidney Function: Because beta-2 microglobulin is filtered by the kidneys and reabsorbed, its levels can rise in the blood when kidney function is impaired. Therefore, it can be used as a marker for kidney disease.
- Use in Cancer Diagnosis and Prognosis: High levels of beta-2 microglobulin can be indicative of certain cancers, such as multiple myeloma or lymphoma. It is often used in the staging and prognosis of these diseases.
- Amyloidosis: Beta-2 microglobulin can accumulate in tissues in a condition known as dialysis-related amyloidosis, particularly in patients with long-term kidney failure and on dialysis. This accumulation can lead to various clinical problems, including joint pain and bone cysts.
In summary, beta-2 microglobulin plays an important role in the immune system and serves as a useful biomarker in various medical conditions, particularly those related to the immune system, kidney function, and certain types of cancer.