Differentiate between antigens, epitopes, and haptens

Antigens, epitopes, and haptens are all related to the immune response in the body, but they have different roles and characteristics.

1. Antigens: These are substances that can induce an immune response in the body. They are typically foreign substances such as bacteria, viruses, or other harmful substances. When an antigen enters the body, it triggers the immune system to produce antibodies to fight against it. Antigens can be proteins, polysaccharides, lipids or nucleic acids.

2. Epitopes: Also known as antigenic determinants, these are the specific parts of an antigen that are recognized by the immune system. In other words, they are the regions on the antigen where an antibody can bind. Each antigen has multiple different epitopes, and each epitope can bind to a different antibody. This allows the immune system to recognize and respond to a wide variety of antigens.

3. Haptens: These are small molecules that can't induce an immune response on their own. However, when they bind to a larger protein (becoming a carrier), they can then be recognized as an antigen. This is because the combination of the hapten and the protein creates a new epitope that the immune system can recognize. Common examples of haptens include drugs, synthetic materials, and some components of animal venoms.

In summary, antigens are the substances that trigger an immune response, epitopes are the parts of antigens that antibodies bind to, and haptens are small molecules that can become antigenic when attached to a protein.