nonself

from The Collaborative International Dictionary of English v.0.48

nonself \non"self`\, n.
   1. That which is not oneself.
      [PJC]

   2. (Immunology) Any material that enters the body and is not
      recognized by the immune system as being part of its body,
      thereby triggering an immune response; any material
      appearing to the immune system to be foreign to its body.
      [PJC]