antibody

American  

[an-ti-bod-ee] / ˈæn tɪˌbɒd i /

noun

plural

antibodies

1. any of numerous Y -shaped protein molecules produced by B cells as a primary immune defense, each molecule and its clones having a unique binding site that can combine with the complementary site of a foreign antigen, as on a virus or bacterium, thereby disabling the antigen and signaling other immune defenses. Ab

2. antibodies of a particular type collectively.

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antibody British  

/ ˈæntɪˌbɒdɪ /

noun

1. any of various proteins produced in the blood in response to the presence of an antigen. By becoming attached to antigens on infectious organisms antibodies can render them harmless or cause them to be destroyed See also immunoglobulin

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antibody Scientific  

/ ăn′tĭ-bŏd′ē /

1. Any of numerous proteins produced by B lymphocytes in response to the presence of specific foreign antigens, including microorganisms and toxins. Antibodies consist of two pairs of polypeptide chains, called heavy chains and light chains, that are arranged in a Y-shape. The two tips of the Y are the regions that bind to antigens and deactivate them.

2. Also called immunoglobulin

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Closer Look

Like other vertebrates, humans possess an effective immune system that uses antibodies to fight bacteria, viruses, and cancer cells. Antibodies are complex, Y-shaped protein molecules. The immune system's B lymphocytes, which are produced by the bone marrow, develop into plasma cells that can generate a huge variety of antibodies, each one capable of combining with and destroying an antigen, a foreign molecule. Antibodies react to very specific characteristics of different antigens, binding them to the top ends of their Y formation. Once the antibody and antigen combine, the antibodies deactivate the antigen or lead it to macrophages(a kind of white blood cell) that ingest and destroy it. High numbers of a particular antibody may persist for months after an invasion, eventually diminishing. However, the B cells can quickly manufacture more of the same antibody if exposure to the antigen recurs. Vaccines work by “training” B cells to recognize and react quickly to potential disease molecules.

Etymology

Origin of antibody

First recorded in 1895–1900; anti- + body

Compare meaning

How does antibody compare to similar and commonly confused words? Explore the most common comparisons:

• antigen vs. antibody

Explanation

An antibody is a protein made by the body that latches onto foreign bacteria and viruses to make them ineffective. Each antibody is designed to target a particular opponent. A powerful part of the body’s immune system, an antibody is produced when the body senses an invader — called an antigen that it doesn’t think should be there. The body then sends out the antibody to neutralize it. Don’t think of an antibody as being anti or “against” your body; think of the body in the word antibody as the antigen, or foreign body that is being fought. Known antibodies have been especially useful in the creation of vaccines.

Example Sentences

Patients who lack the ability to access this diversity-generating process—including those suffering from a condition known as hyper IgM—remain dangerously vulnerable to infection and often require antibody infusions for life.

From The Wall Street Journal • Apr. 20, 2026

The cancerous plasma cells produce large amounts of an abnormal antibody called M protein, which builds up in bone marrow and forms tumors in bones, like the one in my hip.

From Slate • Mar. 29, 2026

Studies on the blood of healthy 15 to 22-year-olds will assess antibody levels to see if current young adults have been left more vulnerable.

From BBC • Mar. 27, 2026

The biotech company released positive data for a Phase 2 study evaluating the efficacy of zumilokibart, a monoclonal antibody targeting proteins related to inflammation, in patients with atopic dermatitis.

From Barron's • Mar. 23, 2026

It has recently been learned that the genes for the marking of self by cellular antigens and those for making immunologic responses by antibody formation are closely linked.

From "The Lives of a Cell" by Lewis Thomas

Related Words

• bacterium
• bug
• disease
• microbe
• microorganism
• pathogen
• virus