?2-Microglobulin (?2M) is a small serum protein that constitutes the light chain of the major histocompatibility class I human leukocyte antigen (HLA class I), an integral membrane protein involved in the immune response. The protein is 99 amino acid residues in length and has molecular mass of 12 kDa (1 - 4). ?2M is released from the cell surface of HLA class I into the serum and carried to the kidneys for degradation and secretion (5). In chronic renal failure,