Sequential localization of antibody to multiple regions of the glomerular capillary wall in passive Heymann nephritis

Passive Heymann nephritis was produced in rats by injection of the multispecific anti-Fx1A antibody. At time points 1 hour, 1 day, 2 days, 3 days, and 4 days groups of rats were sacrificed and their kidneys fixed by retrograde perfusion with paraformaldehyde lysine periodate. The antibody was visualized by direct immunofluorescence and by 125I-Protein-A electron microscopic autoradiography. Localization of the antibody in the lamina rara interna, lamina densa, lamina rara externa and the glomerular epithelial cell was determined by electron microscopic autoradiography according to the method of Saltpeter, Fertuck, and Saltpeter (Saltpeter MM, Fertuck MC, Saltpeter EE: J Cell Biol 72:161, 1977). At least 100 grains/kidney were analyzed. At one hour the antibody was localized in a linear, discontinuous pattern by immunofluorescent microscopy. Ultrastructurally, the antibody was present in all regions of the capillary wall although predominantly in the lamina rara interna. At later time points the immunofluorescence staining changed to the typical granular pattern with majority of the grains localizing to the lamina rara externa and the cell body of the glomerular epithelial cell. The importance of these observations is several-fold. (a) It suggests the involvement of multiple antigens in the pathogenesis of Heymann nephritis. (b) The initial reaction to the lamina rara interna may be potentiating the eventual formation of deposits in the lamina rara externa by locally permeabilizing the capillary wall and allowing passage to other antibodies. (c) The immune complexes formed at the various sites in the capillary may be getting shed and trapped in the lamina rara externa resulting in coalescence and genesis of the nephritogenic electron-dense deposits.