Urinary tract glycoprotein: distribution and antigenic specificity

It has previously been demonstrated that the urinary tract contains a unique glycoprotein (GP1) that appears to serve a function in the clearance of pathogenic bacteria. We prepared a panel of monoclonal antibodies (mAbs) to human GP1 and examined its antigenic specificity and distribution in the human urinary tract. This was also observed in relation to another glycoprotein associated with infection, Tamm-Horsfall protein (THP), as well as to URO-5, a protein used in identifying the lower urinary tract. In enzyme-linked immunoadsorbent assays (ELISA), all of the GP1 mAbs reacted with GP1 prepared from both human urine and rabbit bladder mucosa. No immunoreactivity was observed with either THP mAbs or URO-5 mAbs. Western-blot analyses using GP1 mAbs with human urine GP1 preparations detected a single band of approximately 50-52 kDa. Human urinary tract tissues were also examined by immunohistochemical techniques using the GP1 mAbs, commercial THP, and URO-5 mAbs. In paraffin-embedded bladder sections, only GP1 mAbs reacted with the urothelium. Selective staining of distal collecting tubules, renal pelvis, and ureters was demonstrated for GP1 mAbs. Proximal convoluted tubules, loops of Henle, and Bowman's capsule failed to stain for GP1. In the same tissues, THP mAbs reacted with the thick and thin segments of medullary loops of nephrons (Henle's loops). URO-5 mAbs stained fresh frozen sections of bladder urothelium, distal collecting tubules, and portions of Henle's loops; however, they failed to stain paraffin-embedded tissue sections. These GP1 mAbs provide a new tool for biochemical and histochemical investigations of the mucin layer in both healthy and diseased urinary tract tissue.