immunogen

An immunogen is a substance that can trigger an immune response, specifically by activating lymphocytes, which are the body's infection-fighting white blood cells. These substances can be foreign, originating from outside the body (like viruses or bacteria), or they can be self-antigens, which normally do not provoke an immune response but can in cases of autoimmune disorders.1

When an immunogen enters the body, it has specific regions called antigenic determinants that bind to receptor molecules on lymphocytes. This binding stimulates the lymphocytes to multiply and initiate an immune response, which can include producing antibodies or directly attacking the antigen. The amount of antibody produced depends on the type and quantity of the immunogen, how it enters the body, and individual host characteristics.1