What is the difference between antibody and antigen?

Antibodies are proteins produced by the immune system in response to the presence of antigens. Antigens are molecules that can trigger an immune response, such as viruses, bacteria, or other foreign substances. Antibodies specifically bind to antigens and help the immune system to recognize and neutralize them. In summary, antigens are foreign substances that trigger an immune response, while antibodies are proteins produced by the immune system to target and neutralize antigens.

Antibody

- Produced by B cells
- Recognizes and binds to a specific antigen
- Neutralizes or destroys the antigen
- Y-shaped structure with two heavy chains and two light chains
- Variable region (Fab) binds specifically to the antigen
- Constant region (Fc) interacts with other immune cells

Antigen

- Foreign substance that triggers an immune response
- Recognized by T cells and B cells
- Can be a molecule on the surface of a cell or a free molecule
- Variable in structure, but contains epitopes that are recognized by antibodies
- Many epitopes on a single antigen
- Can be a protein, carbohydrate, lipid, or nucleic acid