In situ immune complex formation in isolated perfused kidney using homologous antibody

The pathogenesis of Heymann nephritis (HN), a morphologic and immunohistologic model for the human membranous glomerulonephropathy, is controversial. To determine the presence of the offending antigen in glomeruli, the specific disease-producing brush border antibody (BBAb) of homologous origin was infused into isolated perfused rat kidney. The antibody was obtained from the acid eluates of kidneys from rats with severe HN and purified using ion exchange and gel filtration chromatography. Its molecular size and IgG nature were ascertained by gel filtration, sucrose density gradient ultracentrifugation, and immunoelectrophoresis, and its specificity by indirect immunofluorescence. Isolated perfused kidneys were perfused with 0.5 to 10 mg. of BBAb; three control groups of kidneys were perfused with buffer only, normal rat IgG, and BBAb absorbed with a renal cortical fraction FX1A, respectively. The ischemia time ranged from 24 to 34 minutes. Localization of BBAb was noted in glomerular capillaries and mesangium and in the walls of blood vessels of many sizes. Normal rat IgG and absorbed BBAb did not show any localization. These results show that the putative antibody of HN when injected into a perfused, bloodless, ischemic kidney combines specifically with an antigen which under the above conditions can be demonstrated in the glomerular capillaries and other blood vessels. Although this represents in situ immune complex formation, which may be suspected of occurring in active HN, the conditions of the isolated perfused kidney under which this occurs are clearly unphysiologic. Whether it indeed takes place in the physiologic in vivo state will require further studies.