What is an antibody?

An antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. Examples of antigens include microorganisms (bacteria, fungi, parasites, viruses) and chemicals.

Here are the steps of how an antibody works:

1. Recognition: Each antibody recognizes a specific antigen unique to its target. This is because at one end of the antibody is a special paratope that is formed to fit a specific epitope on the antigen.

2. Binding: Once the antibody recognizes its specific antigen, it binds to it. This is often compared to a lock and key mechanism where the antibody (the lock) can only be activated by the antigen (the key).

3. Tagging: The antibody marks the antigen so that other cells of the immune system can recognize and destroy it. This process is called opsonization.

4. Neutralization: Antibodies can also neutralize threats directly. They can bind to viruses or bacteria and block their components, preventing them from entering or damaging healthy cells.

5. Stimulation of other immune responses: After an antibody has bound to an antigen, the Fc region of the antibody can also interact with complement proteins and cell receptors, further enhancing the immune response.

In summary, antibodies play a crucial role in the immune system by recognizing and binding to specific antigens, such as viruses or bacteria, and then neutralizing them or marking them for destruction by other immune cells.