Antibody-induced redistribution of Heymann antigen on the surface of cultured glomerular visceral epithelial cells: possible role in the pathogenesis of Heymann glomerulonephritis

In this study we analyze the ability of antibodies that produce passive Heymann glomerulonephritis to induce antigen redistribution on the surface of cultured glomerular visceral epithelial cells (GEC). Polyclonal antibodies produced by immunization with membrane vesicles prepared from proximal tubule brush borders (BB) and polyclonal (rabbit) and monoclonal (mouse) antibodies to a membrane glycoprotein (gp 330) purified from epithelial cells of rat proximal tubule were used. The study by immunofluorescence of GEC kept at 4 degrees C or fixed with paraformaldehyde showed that the three antibody preparations reacted with the plasma membrane in a punctate pattern known to be due to staining of coated pits or coated vesicles on the cell surface. At 37 degrees C and, at a slower rate, at 22 degrees C, the two polyclonal antibodies induced a rapid clustering of antigen-antibody complexes on the nonadherent surface of living cultured GEC with subsequent formation of patches and caps and, after prolonged incubation, with temporary disappearance of Heymann antigen from the cell surface, so-called antigenic modulation. Antigen redistribution and modulation were inhibited by sodium azide, indicating that these processes are energy dependent. Monovalent Fab fragments of antibodies to BB vesicles did not alter the distribution of Heymann antigen unless they were subsequently cross-linked. Monoclonal anti-gp330 induced a modest degree of antigen redistribution, which was increased by subsequent cross-linking. Exposure of glomerular epithelial cells to cytochalasin B, colchicine, or ionophore A23187 prevented or altered antigen redistribution at 37 degrees C. Furthermore, the antibody-induced antigen redistribution was associated with changes in distribution of cytoplasmic actin, myosin, and tubulin, indicating that it is related to the contractile activity GEC. LEW rats, given i.v. injection of IgG directed against BB membrane vesicles, developed passive Heymann glomerulonephritis (i.e., immune deposits in the lamina rara externa of the glomerular basement membrane). In contrast, the glomeruli of rats exposed for longer periods to larger amounts of Fab fragments of the same antibodies failed to develop immune deposits. These studies show that the antibodies to the nephritogenic antigen of Heymann glomerulonephritis may induce a redistribution of immune complexes (IC) in the membrane of glomerular epithelial cells that is similar to that produced by other plasma membran