[Characterization of membrane antigens from human kidney and renal adenocarcinoma]

The brush border of the proximal tubule of human kidney consists of peripheral, integral as well as of transmembranous antigens. Peripheral (surface) antigens are associated with the presence of 5-7 nm globular particles sensitive to limited proteolysis; particles were found to contain a multienzyme complex and exhibited strong affinity towards ConA and WGA. PM-antigens can be solubilized from different portions of PM by differential treatment with proteases and detergents. Labelled antisera against isolated surface glycoproteins reveal a specific reaction with luminal PM of the proximal tubule only, supporting their value for quantitative image analysis (histometry) of kidney tissue sections and for screening of tissue-proteinuria. PM were capable of binding cationic serumproteins (esp. immunoglobulin) and certain O/K-antigens from E.coli, where adhesion was observed on peripheral and intrinsic PM-antigens as well. Major markers of the distal tubule are Tamm-Horsfall protein (cytoplasmic compartment) and a PNA-binding glycoprotein originating from the luminal PM. PM from renal adenocarcinoma exhibit not the globular surface structure found in renal PM, show low immunogenicity, a modulation in the glycosylation pattern of the marker gamma-Glu-transpeptidase and are characterized by a marked depletion of normally differentiated renal antigens. Due to solubilization experiments the presence of cryptic antigens are likely. In addition common determinants between cancer antigens and distinct proteins of the distal tubule and placental trophoblast became apparent.