An Indirect Lectin Affinity Bioassay for Uromodulin

Uromodulin, also known as Tamm-Horsfall glycoprotein (THG), derived from human pregnancy urine, is a monomeric glycoprotein of 85 kDa. It is produced in the thick ascending limb (TAL) and early distal convoluted tubule (DCT) and is excreted in large amounts in urine. The immunosuppressive property of Uromodulin is based on its glycosylation pattern that is different THG obtained from males and nonpregnant women. Although the exact physiological functions of uromodulin are yet to be clarified, a number of researchers have reported its possible involvement in the regulation of ion transport, the urine-diluting mechanism of nephrons, the pathogenesis of stone formation and in some forms of acute renal failure. Uromodulin has also been reported to have a high binding affinity for tumor necrosis factor (TNF). Several assay methods have been developed to quantify uromodulin. Among these, radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) are widely used. Although immunoassays are selective and sensitive, these methods rely on the availability of specific polyclonal or monoclonal antibodies. This study reports a sensitive and specific bioassay for uromodulin without the presence of antibodies. The bioassay is based on the lectin affinity of the glycoprotein and the known interaction between uromodulin and TNF. The results are monitored by using the mortality index of a mouse fibroblast L929 cell line.