What is the difference between antibodies and antigens?

Antibodies and antigens are two key components of the body's immune system that work together to protect against foreign invaders like bacteria and viruses. While they are closely related and interact with each other, they have distinct roles and characteristics:

Antibodies:

- Antibodies are proteins produced by the immune system in response to the presence of antigens.

- They are also known as immunoglobulins (Ig).

- Antibodies are Y-shaped molecules with two identical heavy chains and two identical light chains.

- Each antibody has a unique antigen-binding site that specifically recognizes and binds to a particular antigen.

- Antibodies can neutralize toxins, tag foreign cells for destruction by other immune cells, and activate the complement system, which is a group of proteins that help destroy invading microorganisms.

- There are different classes of antibodies, including IgG, IgA, IgM, IgD, and IgE, each with specific roles and locations in the body.

Antigens:

- Antigens are molecules that trigger an immune response by the body.

- They can be proteins, carbohydrates, lipids, or nucleic acids.

- Antigens are usually foreign substances such as bacteria, viruses, toxins, or foreign tissue.

- When an antigen enters the body, it is recognized by antigen-presenting cells (APCs) such as macrophages and dendritic cells, which process the antigen and present its fragments on their cell surface.

- The antigen fragments are then recognized by specific antibodies, which bind to them, leading to the activation of the immune system.

- Antigens can be highly specific, and the body can distinguish between self and non-self antigens, which helps prevent autoimmune responses.

In summary, antibodies are proteins produced by the immune system in response to antigens and are designed to bind specifically to and neutralize antigens, while antigens are molecules that trigger an immune response by being recognized by antibodies and immune cells.