Identification of an early expressed marker of the luminal membrane of rabbit small intestinal columnar cells. Presence of a homologous antigen in kidney proximal tubules and glomeruli.

Four monoclonal antibodies have been produced that specifically react with a rabbit intestinal brush-border glycoprotein which migrates in SDS-polyacrylamide gel electrophoresis as a protein of molecular weight 140,000. Contrarily to brush-border hydrolases, it is expressed in poorly differentiated crypt cells of the small intestine. Absent from colon columnar cells, it can be considered to be an early marker of differentiation of absorbing cells of the small intestine. Immunofluorescence technique showed the presence of a homologous antigen in kidney proximal tubule brush-border and podocytes of kidney glomeruli.