Urinary Kidney-Derived Antigens Determined by Tests Built on Monoclonal Antibodies: New Markers for Kidney Damage

We have developed a series of sandwich ELISA for the quantitation of kidney derived urinary antigens (UA) utilizing monoclonal antibodies specific for antigens localized in cells of defined subunits of the nephron of human kidney. Antigens derived from the distal and proximal parts of the tubular system as well as antigens localized over its entire length can be detected and quantified in urine samples. Antigen excretion was measured in the urine of healthy individuals, patients with various diseases with and without kidney involvement, kidney transplant recipients, and healthy volunteers after receiving antibiotics. Low antigen excretion values were found in healthy individuals, patients with diseases primarily affecting the glomerulus, and inactive phases of chronic diseases. Toxic side effects of drugs were reflected by slightly (antibiotic drugs) or strongly (cytostatic drugs) enhanced antigenuria. Excretion of some or all of the antigens was always indicative of massive alteration of tubular structures, such as in acute phases of tubulointerstitial disease or during rejection episodes in kidney transplant recipients. The results obtained indicate that it is possible to obtain information on the location and extent of acute primary processes in the kidney with these tests.