Interaction of urinary Tamm-Horsfall protein with transitional cells and transitional epithelium

Uropathogenic E. coli that express mannose sensitive adhesins adhere to agglutinated urinary Tamm-Horsfall protein (THP) and to exfoliated transitional epithelial cells coated with THP. Whether THP interacts with the transitional epithelium in vivo and facilitates adhesin mediated attachment of E. coli is not known. Using immunohistochemical techniques we could not identify THP associated with formalin-fixed, paraffin-embedded transitional epithelium from a variety of sites within the urinary tract. However, varying levels of THP associated with the washed exfoliated transitional cells from 10 different subjects were detected by indirect radioimmunoassay methodologies. After in vitro incubation in human urine the mean interaction of THP with the exfoliated transitional cells increased significantly but closely paralleled the mean interaction of THP with exfoliated vaginal and buccal epithelial cells after identical incubation. We conclude that the interaction of THP with transitional cells in vivo is nonspecific and occurs after detachment from the mucosa. THP may act as a natural host defense against E. coli bacteriuria by inhibition of adhesion mediated bacterial adherence to the urothelium.