Monoclonal antibodies to human glomerular antigens

Using cultured human fetal kidney cortical cells as antigen, two monoclonal antibodies (moAbs) against human glomeruli were produced. One of these moAbs, H-4, recognized the cell surface of glomerular epithelial cells, and the other, H-13, recognized the extracellular matrix present in the mesangial area. Both also reacted with liver, H-4 recognizing antigen present on the hepatocyte, and H-13 recognizing antigen distributed along the sinusoid. Species specificity for these moAbs was examined using mouse, rat, guinea pig and rabbit glomeruli, which revealed that H-4 reacted with rat glomerular epithelial cells and H-13 stained guinea pig glomerular mesangium. In the human fetal kidney, H-13 reacted with the mesangium, glomerular and tubular basement membrane and Bowman's capsule, and H-4 with the glomerular and tubular epithelial cells. Dot immunobinding assay of fibronectin purified from glomerular culture supernatant and plasma revealed that H-13 recognized both plasma and cellular fibronectin. Immunoblot analysis of 2.0 M guanidine HCl extract after dissociation in sodium dodecyl sulfate and electrophoresis demonstrated binding of H-4 to a 125 kd polypeptide. Immunoblot analysis of thermolysin-digested fibronectin exhibited binding of H-13 to 145 kd and 110 kd fragments, but not to 38 kd-29 kd fragments. In renal biopsy specimens from patients with membranous nephropathy. H-13 stained the glomerular basement membrane (GBM), but not the mesangium, whereas anti-fibronectin antisera stained both the GBM and the mesangium. In those from patients with minimal change nephrotic syndrome (MCNS), IgA glomerulonephritis (IgAGN) and membranoproliferative glomerulonephritis (MPGN), the staining pattern with H-13 was similar to that with polyclonal anti-fibronectin antisera. These results indicate that H-4 recognizes a 125 kd polypeptide constituent of the glomerular epithelial cell membrane and that H-13 recognizes the cell binding domain of fibronectin as well as revealing structural alterations in the mesangium and GBM.