Murine monoclonal antibodies have proven to be invaluable tools in medical research and diagnosis. However, their use as therapeutic agents remains limited since these proteins can act as foreign antigens in the human host. An immune response subsequent to administration of monoclonal antibodies may result in unpredictable in vivo distribution and insufficient interaction with cellular or molecular targets of the immune system. Also, the patient may produce anti-anti-bodies that can neutralize the effects of the therapeutically administered monoclonal antibodies. Treatment of autoimmune disease is an important potential therapeutic application of monoclonal antibodies, provided that these difficulties can be overcome.