More recently, monoclonal antibodies are being used to suppress the immune system, and several antibodies are now approved for the treatment of autoimmune diseases. These antibodies are typically “humanized” mouse monoclonal , created by transposing the mouse antigen-binding sites onto a human antibody framework. This technique retains the full range of effective properties of human Fc while minimizing the immunogenicity of the mouse component. Antibodies that target the immune system can target cell surface molecules on T or B cells or can target soluble mediators of inflammation such as cytokines. Among the most effective uses of monoclonal antibodies has been in treating severe rheumathoid arthritis, using monoclonal antibody directed against tumor necrosis factor (TNF-α). The drawback to this therapy is that the infusion must be repeated frequently to sustain results.