<immunology> A substance which is capable of eliciting (inducing) an immune response. An immunogen usually has a fairly high molecular weight (usually greater than 10,000), thus, a variety of macromolecules such as proteins, lipoproteins, polysaccharides, some nucleic acids, and certain of the teichoic acids, can act as immunogens.

Compare: antigen.

(09 Oct 1997)