The Rat B2M Assay Kit provides the assay-specific components for the quantitative determination of beta-2-microglobulin (B2M) in rat urine. B2M is an 11.8 kDa secreted and ubiquitously expressed protein that is involved in the presentation of peptide antigens to the immune system. B2M is normally filtered in the kidneys through the glomerulus, reabsorbed, and metabolized in the cells of the proximal tubules. Under normal conditions, trace amounts of B2M are excreted in the urine. The levels of B2M rise in the event of kidney toxicity associated with glomerular injury and/or renal tubular damage. Elevated serum B2M levels have also been reported in conditions involving reduced Glomerular Filtration Rate (GFR) as well as allograft rejection in patients undergoing kidney transplant.