Scanning electron microscopy of immune complexes in membranous glomerulopathy

Scanning electron microscopy (SEM) was done on seven cases of membranous glomerulopathy (MG) in order to describe the morphologic appearance of the immune complexes that are deposited in the glomerular basement membranes, as previous SEM studies on the human glomerulus primarily focused on the changes in the podocytes. The diagnosis of membranous glomerulopathy of idiopathic form or secondary to systemic lupus erythematosus was confirmed by conventional light and transmission electron microscopy and immunofluorescent microscopy. By SEM, the external surfaces of the basement membranes were covered by immune complexes that appeared as a network of "lumpy-bumpy" deposits. They were arranged in anastomosing cords imparting a "swiss cheese" pattern. The immune-complex nature of these anastomosing cords of deposits is confirmed by our preliminary immunoscanning electron-microscopic study. The exact mechanism for immune complexes to be localized on the external surface of the basement membrane remains to be elucidated.