A monoclonal antibody to a rat hepato-renal membrane antigen

A monoclonal antibody against a membrane glycoprotein of rat hepatocytes has been produced. The nature of this antibody designated as HAM.4 was analysed by cellular radioimmunoassay, flow cytofluorography and indirect immunoperoxidase procedures. The following characteristics of HAM.4 were elucidated. First, an immunohistochemical study revealed that this antibody stained preferentially the bile canalicular face of hepatocyte membrane. Secondly, HAM.4 cross-reacted with kidney, spleen and thymus as well as liver. The kidney expressed much more the antigen molecules detected by this antibody than the liver did. The antigen was located predominantly on the brush border of proximal tubules in kidney. Thus, HAM.4 would be useful for analysing one of the brush border antigens of renal tubules which has been thought to be a pathogenic antigen for inducing experimental membranous glomerulonephritis. Finally, HAM.4 failed to label the cell membrane of rat hepatoma cell lines examined, indicating that the antigen detected by HAM.4 may disappear from cell surface during the course of hepatocarcinogenesis.