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

Each order includes four rapid antigen Covid-19 tests. —Amanda Musa, CNN, 5 Mar. 2024

That could effectively open up one of the seats in the vaccines, dropping them next season from quadrivalent formulations – targeting four different antigens in a single shot – to trivalent. —Alexander Tin, CBS News, 29 Feb. 2024

And antigens are also sneaky, sometimes tucking away into parts of the brain that aren’t easy to access. —Isabella Cueto, STAT, 21 Feb. 2024

In screening, his score in a prostate specific antigen (PSA) test had been climbing for a couple of years. —Dan Lamothe, Washington Post, 28 Jan. 2024

The high-dose shot contains four times the amount of antigen – that is, the protein molecule identified with the virus – to trigger a stronger immune response, while the recombinant shot contains three times the amount of antigen. —Mary Kekatos, ABC News, 2 Nov. 2023

The problem is that urine antigen tests are less accurate in milder cases of pneumonia. —Tanya Feke, Verywell Health, 4 Apr. 2024

Another study, which tested the accuracy of rapid antigen tests from 2020 to 2022, found similar results. —Anuradha Rao, The Conversation, 1 Mar. 2024

Each order includes four individual rapid antigen COVID-19 tests. —Brianna Taylor, Sacramento Bee, 1 Mar. 2024

Word History

Etymology

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

First Known Use

1908, in the meaning defined above

Phrases Containing antigen

• antigen-presenting cell
• carcinoembryonic antigen
• human leukocyte antigen
• prostate-specific antigen

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