What are antibodies?

What are antibodies, what produces them, and what do antibodies do?

What are antibodies, what do antibodies do and what produces them? Read on to find out…

What are antibodies?

Antibodies are large proteins, shaped like the letter Y, that function as a vital part of the adaptive immune system of vertebrates.

They travel the body through the circulatory and lymphatic systems, binding to and defending against antigens such as foreign proteins, bacteria, viruses, cells, and allergens.

Also known as immunoglobulin (Ig), antibodies are one of the best defenses against antigens, binding on to antigens with the tips of the Y structure. The tip of the antibody structurally binds to a matching part of the antigen, acting like a lock and key that fit together specifically and uniquely.

The antibody for one antigen cannot bind to a different antigen. For example, the antibody for the tuberculosis bacterium cannot recognize the polio virus.

Simple in their makeup, antibodies are made of two heavy chains that make the Y shape and two light chains that reinforce the upper arms of the Y. There are only two types of light chain (lambda, λ and kappa, κ) but there are five types of heavy chain (alpha, α; gamma, γ; delta, δ; epsilon, ε; mu, μ), which define the type of antibody. Thus, there are 5 types of antibodies, IgA, IgD, IgE, IgG, and IgM, each found in different tissue types and having slightly different functions.

Despite the small number of different antibody types, humans can generate about 10 billion specific antibodies. This is because there is a very small area on the end of each arm of the Y that is tremendously variable, allowing a huge variety of antibodies to be produced. This variety in antibodies allows the immune system to recognize an equally huge variety of antigens.

What produces antibodies?

Antibodies are produced by special types of white blood cells called B-cells (or plasma cells). These B-cells have 50,000 to 100,000 antibodies bound to their surfaces and when they come across an antigen and bind to it, the B-cells produce millions of antibodies into the bloodstream and lymphatic system.

What do antibodies do?

These antibodies attack any antigens that have the same structure as the one that activated the B-cell. The antibodies binding to the antigens can either block parts of the antigens, preventing them from functioning, or they can tag the antigen, alerting other cells to destroy the antigen. This is done by large cells that engulf and digest the invader (phagocytosis), or by a series of chemical reactions that cause the invading cell to explode (lysis).

B-cells also divide and give rise to memory cells that remember the antigen for the future. If it is encountered again, the system is able to make antibodies immediately. This is how vertebrates acquire immunity against diseases after being infected with them.

Vaccines are based on this premise. A vaccine introduces a weakened antigen into the body, causing the immune system to produce antibodies in response. The memory cells produced by the immune response remain in the immune system so that if a person encounters the disease again, they already have the ability to manufacture the correct antibodies right away, effectively protecting against the disease.

Blood types are also antibody-based. The two most important blood typing systems, ABO and Rh, are based on the types of antigens a person has on the surface of their red blood cells, and the antibodies in their blood plasma. Antibodies can be used for many things outside the body, including diagnosis of disease, therapy for diseases such as arthritis, multiple sclerosis, and many forms of cancer, and prenatal therapy for Rh incompatibility.

A powerhouse in the immune system, with versatile applications in the medical field, antibodies employ incredibly sophisticated mechanisms to help defend against invaders that most organisms won’t ever know were there.

Summary

What are antibodies?

Antibodies are large proteins, shaped like the letter Y, that function as a vital part of the adaptive immune system of vertebrates.

What produces antibodies?

Antibodies are produced by special types of white blood cells called B-cells (or plasma cells).

What do antibodies do?

Antibodies attack any antigens that have the same structure as the one that activated the B-cell.