Definition - What does Immunogen mean?
An immunogen is any antigen or other substance that is able to elicit an immune response within the body. In order to produce such a response, immunogens must be made up of the requisite epitopes and macromolecular carriers that will cause such a reaction. Immunogens can be utilized in immunoassay drug screenings to indicate that a drug has been metabolized by the body.
SureHire explains Immunogen
Immunogens and their immune system reactions in the body can be employed in immunoassay drug testing to detect the presence of drug metabolites in a urine sample by specifically monitoring for a reaction between immunogens and antibodies. The reaction monitored can only return a positive or negative result, which indicates the previous presence of certain classes of drugs, such as amphetamines or opioids. This reaction does not identify the specific drugs, nor does it measure the amount of the drug present in the sample.