immunogen

from WordNet (r) 3.0 (2006)

immunogen
    n 1: any substance or organism that provokes an immune response
         (produces immunity) when introduced into the body [syn:
         {immunogen}, {immunizing agent}]

from The Collaborative International Dictionary of English v.0.48

immunogen \immunogen\ n.
   any substance that produces immunity when introduced into the
   body.
   [WordNet 1.5]

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