Immunoelectron Microscopic Diagnosis In Nephropathology

An immunogold postembedding method for the ultrastructural localization of immunoglobulin G (IgG), IgA, IgM, C3, fibrinogen, and kappa and lambda immunoglobulin light chains was established. The method was performed on surplus tissue from renal biopsies fixed in 2% glutaraldehyde and embedded in acrylic LR White resin. Fifteen cases were studied and the localization of antigen in the dense deposits in glomeruli compared with the immunofluorescence (IF) findings on the same cases. The results obtained by IF and immunoelectron microscopy (IEM) were comparable for IgG and IgA. In most instances, IgM and C3 were more intensely labeled by IF than IEM. Some discrepancies were noted for fibrinogen. It is postulated that these differences are related to a partial loss of antigenicity due to fixation or chemical reaction with the embedding medium. The advantage of IEM resides in localizing antigens in very small deposits seen in early stages of glomerulonephritis. The method can supplement IF in diagnostically difficult cases or be substituted for it when material for IF is not available.