What is the Difference Between Antigen and Immunogen?

The terms antigen and immunogen are often used interchangeably, but they describe two different types of interactions between a molecule and the immune system. Here are the key differences between the two:

• Antigen: An antigen is a molecule that is capable of binding to the product of an immune response, such as an antibody or a T-cell receptor. Antigens can be proteins, carbohydrates, lipids, or nucleic acids.
• Immunogen: An immunogen is a molecule that is capable of eliciting an immune response by an organism's immune system. Immunogens are functional entities that activate, stimulate, or trigger the immune system components.

All immunogens are antigens, but not all antigens are immunogens. Some very small molecules called haptens can bind to antibodies or B-cell receptors but cannot elicit an immune response by themselves. They can be made immunogenic by conjugation to a suitable carrier.

In summary, an immunogen is a molecule that can stimulate an immune response, while an antigen is a molecule that can bind to the products of an immune response. Although all immunogens are antigens, not all antigens have the ability to elicit an immune response like an immunogen can.

Comparative Table: Antigen vs Immunogen

Here is a table highlighting the differences between an antigen and an immunogen:

In summary, an immunogen is a type of antigen that can elicit an immune response, while not all antigens are immunogenic. Immunogenic property is not found in all antigens, and some antigens can be made immunogenic by conjugating with a carrier protein.