antibody
Americannoun
plural
antibodies-
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
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antibodies of a particular type collectively.
noun
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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.
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Also called immunoglobulin
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
Compare meaning
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
Muscle quality for patients with obesity isn’t primarily affected by nerve or muscle-wasting processes and there is generally more myostatin—a protein that regulates muscle growth—for an anti-myostatin antibody like emugrobart to target, it added.
From The Wall Street Journal • Mar. 23, 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
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
