Immunogenicity

Immunogenicity is the ability of a foreign substance, such as an antigen, to provoke an immune response in the body of a human or other animal. It may be wanted or unwanted:

• Wanted immunogenicity typically relates to vaccines, where the injection of an antigen (the vaccine) provokes an immune response against the pathogen, protecting the organism from future exposure. Immunogenicity is a central aspect of vaccine development.^[1]
• Unwanted immunogenicity is an immune response by an organism against a therapeutic antigen. This reaction leads to production of anti-drug-antibodies (ADAs), inactivating the therapeutic effects of the treatment and potentially inducing adverse effects.^[2]

A challenge in biotherapy is predicting the immunogenic potential of novel protein therapeutics.^[3] For example, immunogenicity data from high-income countries are not always transferable to low-income and middle-income countries.^[4] Another challenge is considering how the immunogenicity of vaccines changes with age.^[5][6] Therefore, as stated by the World Health Organization, immunogenicity should be investigated in a target population since animal testing and in vitro models cannot precisely predict immune response in humans.^[7]

Antigenicity is the capacity of a chemical structure (either an antigen or hapten) to bind specifically with a group of certain products that have adaptive immunity: T cell receptors or antibodies (a.k.a. B cell receptors). Antigenicity was more commonly used in the past to refer to what is now known as immunogenicity, and the two terms are still often used interchangeably. However, strictly speaking, immunogenicity refers to the ability of an antigen to induce an adaptive immune response. Thus an antigen might bind specifically to a T or B cell receptor, but not induce an adaptive immune response. If the antigen does induce a response, it is an 'immunogenic antigen', which is referred to as an immunogen.