Microglobulin ELISA - Beta-2

Enzyme Immunoassay for the Quantitative Determination of Beta-2-Microglobulin Concentration in Human Serum

FOR RESEARCH USE ONLY. NOT FOR USE IN DIAGNOSTIC PROCEDURES

SUMMARY
?2 microglobulin also known as B2M is a component of MHC class I molecules, which are present on all nucleated cells (excludes red blood cells). In humans, the ?2 microglobulin protein is encoded by the B2M gene. In patients on long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces, a disease known as dialysis-related amyloidosis.

Mice models deficient for the ?2 microglobulin gene have been engineered. These mice demonstrate that ?2 microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In fact, in the absence of ?2 microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface. In the absence of MHC class I, CD8 T cells cannot develop. (CD8 T cells are a subset of T cells involved in the development of acquired immunity.) Low levels of ?2 microglobulin can indicate non-progression of HIV.

Levels of beta-2 microglobulin can be elevated in multiple myeloma and lymphoma, though in these cases primary amyloidosis (amyloid light chain) and secondary amyloidosis (amyloid associated protein) are more common. The normal value of beta-2 microglobulin is <2 mg/L. However, with respect to multiple myeloma, the levels of beta2-microglobulin may also be at the other end of the spectrum. Diagnostic testing for multiple myeloma includes obtaining the beta2-microglobulin level, for this level is an important prognostic indicator. A patient with a level <4 mg/L is expected to have a median survival of 43 months, while one with a level >4 mg/L has a median survival of only 12 months. Beta-2 microglobulin levels cannot, however, distinguish between monoclonal gammopathy of uncertain significance (MGUS), which has a better prognosis, and smouldering (low grade) myeloma.

PRINCIPLE OF THE TEST
The United Immunoassay Beta2-MG ELISA test is based on the principle of a solid phase enzyme-linked immunosorbent assay (ELISA). The assay system utilizes a monoclonal anti-Beta2-MG antibody for solid phase immobilization (on the microtiter wells). A sheep anti-Beta2-MG antibody is in the antibody-enzyme (horseradish peroxidase) conjugate solution. The diluted test sample is allowed to react first with the immobilized antibody for 30 minutes at 37C. The sheep anti-Beta2-MG-HRPO conjugate is then added and reacted with the immobilized antigen for 30 minutes at 37C, resulting in the Beta2-MG molecules being sandwiched between the solid phase and enzyme-linked antibodies.

EXAMPLE OF STANDARD CURVE
Results of a typical standard run with optical density readings at 450 nm shown in the Y axis against Microglobulin concentrations shown in the X axis. This standard curve is for the purpose of illustration only, and should not be used to calculate unknowns. Each user should obtain his or her own data and standard curve.