Definition : Antigens
- Foreign substance that provokes the antibody production when entered in body.
- Substance which, when introduced into the body, stimulates the production of antibodies with which it reacts in specific and observable manner.
- Substances that can induce a specific immune response and specifically bind products of immune response in vitro or in vivo.
- It can be described as a substance that reacts with the products of a specific immune response. The word originated from the notion that they can stimulate antibody generation.
- Substances that can be recognized by the immunoglobulin receptor of B cells, or by the Tcell receptor when complexed with MHC, are called antigens.
Definition : Immunogens
- Immunogens are substances capable of stimulating the immune system (that is, eliciting B or T cell response) and reacting with the product of such stimulation
“Not all antigens are immunogens but all immunogens are antigens”
Immunogenicity vs Antigenicity
- Immunogenicity is the ability to induce a humoral and/or cell mediated immune response
B cells + Antigen —-> Plasma cells + Memory Cells
T cells + Antigen + MHC —> T effector cells + Memory Cells
- Antigenicity is the ability to combine specifically with the final products of the immune response (i.e. secreted antibodies and/or surface receptors on T-cells).
- Although all molecules that have the property of immunogenicity also have the property of antigenicity, the reverse is not true.
- An immunogen is able to induce an immune response, whereas an antigen is able to combine with the products of an immune response once they are made.
