Acute glomerulonephritis after intravenous injection of monoclonal anti-thymocyte antibodies in the rat.

Female Wistar rats were injected with (mouse) monoclonal antibodies (Moabs) of different IgG subclasses directed to rat thymocytes or rat tumor cells. Following intravenous injection of antithymocyte Moabs, glomerular binding of mouse IgG was observed during the first 4 days along the GBM and in the mesangium. No staining for mouse IgG was detected in anti-tumor Moab injected rats. Animals injected with IgG 2a anti-thymocyte Moab developed glomerulonephritis and a massive proteinuria in contrast to rats injected with IgG 1 Moab which is non-complement fixing. The glomerulonephritis lesion consisted of microaneurysms and focal and segmental proliferation. Deposits of complement and fibrin could be detected exclusively in rats injected with IgG 2a anti-thymocyte Moab during the whole observation period of 14 days. This is the first demonstration of overt glomerulonephritis lesions on the injection of monoclonal antibodies.