Intrarenal complement fixation by cytotxic antibodies.

The reactivity of histocompatibility antigens with serum antibodies and complement was studied in a short term model of allotransplantation. Lewis and DA rat kidneys were perfused with cytotoxic antisera and tissue sections analyzed for adsorption of fluorescent antibodies against gamma-globulin and complement (beta(1C) protein). Both, the presumed cytotoxic antibody and C were localized at similar sites in the endothelial lining and in the walls of the arterial vessels and of the larger veins. The pattern of immune globulin deposition was distinct from that observed in glomerulonephritis. It may thus become helpful in the differential diagnosis between graft rejection and glomerulonephritis. At the sites of the deposits, the endothelial cells appeared enlarged and their nuclei protruded into the lumen. The findings are in line with the hypothesis that an antibody-mediated local activation of serum complement may be involved in the destruction of allografted tissue.