an·​ti·​gen | \ˈan-ti-jən, -ˌjen\

Definition of antigen 

: any substance (such as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (such as a protein) and that is capable of binding with a product (such as an antibody or T cell) of the immune response

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Other Words from antigen

antigenic \ˌan-​ti-​ˈje-​nik \ adjective
antigenically \-​ni-​k(ə-​)lē \ adverb
antigenicity \-​jə-​ˈni-​sə-​tē \ noun

Did You Know?

An antibody is a protein produced by your immune system to fight outside invaders. Since the enemy substance actually triggers the production of antibodies, such substances are called antigens—anti- being short for antibody, and -gen meaning "producer". (In a similar way, an allergen produces an allergy, and a pathogen produces a pathology or disease.) Antigens are often rodlike structures that stick out from the surface of an invading organism—usually a bacterium or a virus—and allow it to attach itself to cells in the invaded body. But unfortunately for them, in doing so they let the immune system know they're present, and the body is flooded with an army of Pac-Man-like antibodies.

Examples of antigen in a Sentence

Recent Examples on the Web

The variations change the shape of its antigens, allowing it to keep dodging the host’s immune responses. Kiona N. Smith, Ars Technica, "Ancient DNA reveals the secrets of a devastating European disease," 26 Sep. 2018 The Western Blot test measures your body’s antibody response to Borrelia antigens. Andrea K. Mcdaniels,, "Ask the expert: With Lyme disease on the rise, here's how you can protect yourself," 3 July 2018 The team also took blood samples for testing by two conventional and quicker methods: examination under a microscope or screening for antigens with a rapid diagnostic test. Richard Conniff, Scientific American, "Is Malaria’s Peculiar Odor the Key to Its Conquest?," 14 May 2018 Their immune systems can react against blood cells that are marked with certain antigens — surface proteins. NBC News, "Red Cross seeks more blood with #MissingType campaign," 11 June 2018 Other immune therapies under development include vaccines to amp up the immune system, and an approach called CAR-T, for chimeric antigen receptor T cell. Karen Weintraub, STAT, "Once quickly lethal and still humbling, multiple myeloma may be in a ‘golden age’ of treatment," 29 May 2018 The first is a combination investigational antibody and drug that targets a protein called B-cell maturation antigen, or BCMA. Clifton Leaf, Fortune, "GSK’s New CEO Emma Walmsley Has a Strong Start Out of the Gate," 8 June 2018 These treatments include the checkpoint inhibitors Keytruda and Opdivo, CAR-T drugs such as Yescarta and Kymriah, and neo-antigen vaccines. Casey Ross, STAT, "A new cancer care dilemma: Patients want immunotherapy even when evidence is lacking," 4 June 2018 The second type of immunotherapy, used mostly with blood cancers, involves chimeric antigen receptor (CAR) T-cell therapy. Cindy Goodman, miamiherald, "Immunotherapy is giving some cancer patients a new life when they had all but given up | Miami Herald," 25 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'antigen.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of antigen

1908, in the meaning defined above

History and Etymology for antigen

German, from French antigène, from anticorps antibody + -gène -gen

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Last Updated

29 Nov 2018

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Time Traveler for antigen

The first known use of antigen was in 1908

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English Language Learners Definition of antigen

medical : a harmful substance that causes the body to produce antibodies


an·​ti·​gen | \ˈant-i-jən \

Medical Definition of antigen 

: any substance (as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (as a protein) and that is capable of binding with a product (as an antibody or T cell) of the immune response

Other Words from antigen

antigenic \ˌant-​i-​ˈjen-​ik \ adjective
antigenically \-​i-​k(ə-​)lē \ adverb

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More from Merriam-Webster on antigen

Spanish Central: Translation of antigen

Nglish: Translation of antigen for Spanish Speakers

Britannica English: Translation of antigen for Arabic Speakers Encyclopedia article about antigen

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