RESISTANCE TO THERAPY IN MATURE PALMERSTON NORTH MICE TREATED WITH CYCLOPHOSPHAMIDE OR HYDROCORTISONE SODIUM SUCCINATE

recognized model of systemic lupus erythematosus. In this study PN mice with established autoimmune dis-ease were treated until death with cyclophosphamide (8 mg/kg/day) or hydrocortisone (10 mg/kg/day). These doses had previously been found to prevent or suppress disease in another lupus model, the NZB/NZW mouse. In the PN strain, autoantibodies, severity of glomerulo-nephritis, and longevity were not influenced by treat-ment. Furthermore, the incidence of neoplasms was not increased in P N mice receiving prolonged therapy with immunosuppressive drugs. Unlike NZB/NZW mice, P N mice were resistant to the effects of cyclophosphamide and hydrocortisone. Inbred mice of the Palmerston North (PN) strain spontaneously develop a disease similar to systemic lupus erythematosus (SLE) in humans. These animals have positive indirect immunofluorescent tests for anti-nuclear antibodies (ANA), antibodies to DNA (anti-DNA), LE cells, glomerulonephritis, and arteritis (1). The availability of this newly recognized strain of au