antigen

noun

an·ti·gen ˈan-ti-jən

-ˌjen

: 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

antigenic

ˌan-ti-ˈje-nik

adjective

antigenically

ˌan-ti-ˈje-ni-k(ə-)lē

adverb

antigenicity

ˌan-ti-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 tiny amounts of weakened or inactivated viruses and bacteria (known as antigens) in vaccines trigger the immune system to create antibodies that fight against them. —

Rachel Rabkin Peachman, Parents, 21 Sep. 2023 On/Go At-Home COVID-19 Rapid Antigen Test, $8 On/Go's $8 rapid antigen nasal swab test claims to detect a positive or negative result in just 10 minutes with 95 percent accuracy, according to the brand. —

Toni Sutton, Peoplemag, 14 Aug. 2023 All men taking testosterone must be monitored regularly for any rise in their prostate antigen levels. —

Erika Edwards, NBC News, 16 June 2023 Anyone with traditional Medicare can continue getting PCR and antigen tests with no cost-sharing when the lab tests are ordered by a doctor and some other health care providers. —

John Kennedy, Popular Science, 10 May 2023 The antigen builds on work by researchers at the National Institutes of Health that was hailed as one of the top 10 breakthroughs of 2013. —

Alexander Tin, CBS News, 3 May 2023 Doctors recommend if a patient is screened for prostate cancer, prostate specific antigen (PSA) blood tests are used as the primary screening tool. —

Tasmiha Khan, Health, 4 Apr. 2023 Most at-home tests are antigen tests, although a handful of pricier over-the-counter tests are molecular tests, which are more sensitive in a similar way to PCR. —

Theresa Tamkins, NBC News, 10 Sep. 2023 Key Takeaways Experts say SARS-CoV-2 has not mutated enough to go undetected by rapid antigen tests. —

Carla Delgado, Verywell Health, 31 Aug. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'antigen.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

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

First Known Use

1908, in the meaning defined above

Time Traveler

The first known use of antigen was in 1908

See more words from the same year

Cite this Entry

Style

“Antigen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/antigen. Accessed 3 Oct. 2023.

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Kids Definition

antigen

noun

an·ti·gen ˈant-i-jən

-ˌjen

: a substance (as a protein) that causes the body to form antibodies against it when it is introduced into the body either alone or as part of a microscopic plant or animal

antigenic

ˌant-i-ˈjen-ik

adjective

Medical Definition

antigen

noun

an·ti·gen ˈant-i-jən

: 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

antigenic

ˌant-i-ˈjen-ik

adjective

antigenically

-i-k(ə-)lē

adverb