beta2microglobulinderived

Beta-2-microglobulin (β2M) is a small, non-glycosylated protein that forms part of the MHC class I complex. It is the non-polymorphic light chain that associates with the heavy chain of MHC class I molecules in the endoplasmic reticulum and, after proper folding and peptide loading, contributes to the stable expression of the complex on the cell surface. β2M is produced by nearly all nucleated cells and is released into the circulation in small amounts.

Because β2M is freely filtered by the glomeruli and reabsorbed in the proximal tubules, its serum concentration is influenced by renal function. In renal failure or reduced glomerular filtration rate, β2M accumulates in the blood. Prolonged elevated levels in dialysis patients are linked to dialysis-related amyloidosis, a condition in which β2M deposits form amyloid in joints and bones.

Clinically, elevated β2M is observed in various lymphoid and some solid malignancies and can reflect tumor burden. It is a useful prognostic biomarker in multiple myeloma, where higher levels correlate with poorer outcomes and are incorporated into staging systems. Immunoassays such as nephelometry or turbidimetry are used to measure serum β2M; normal levels in healthy adults are typically in the low mg/L range, around 1–3 mg/L, with higher values in renal impairment.