Resistance to therapy in mature Palmerston North mice treated with cyclophosphamide or hydrocortisone sodium succinate.

Inbred Palmerston North (PN) mice are a newly recognized model of systemic lupus erythematosus. In this study PN mice with established autoimmune disease 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 glomerulonephritis, and longevity were not influenced by treatment. Furthermore, the incidence of neoplasms was not increased in PN mice receiving prolonged therapy with immunosuppressive drugs. Unlike NZB/NZW mice, PN mice were resistant to the effects of Cyclophosphamide and hydrocortisone.