A monoclonal antibody used to treat psoriasis (a chronic skin disease). It is also being studied in the treatment of graft-versus-host disease (GVHD) of the skin after a donor stem cell transplant. Efalizumab binds to a molecule called LFA-1, and blocks the action of T cells (a type of white blood cell). It is a type of immunosuppressant. Also called Raptiva.