antigen

IPA/ˈæntɪdʒən/
KK[ˈæntədʒən]IPA/ˈæntɪdʒən/

antigen — noun

  • antigensingular
  • antigensplural

1. A substance that your body recognises as foreign and that makes the immune syste

1.nounB2
Definition

A substance that your body recognises as foreign and that makes the immune system produce proteins called antibodies to attack it — for example, a protein on the surface of a virus or bacterium.

Example

The flu vaccine contains a dead antigen that trains the body to fight infection.

Pollen acts as an antigen for Rin, causing her eyes to water every spring.

acts as an antigen

Common collocations
  • foreign antigen
  • viral antigen
  • surface antigen
  • tumour antigen
  • antigen test
  • antigen-antibody reaction
  • antigen on [virus/surface]
  • acts as an antigen
Synonyms
  • immunogen

    a more technical term for any antigen that reliably provokes an immune response; all immunogens are antigens, but not all antigens are strong immunogens

  • allergen

    a specific type of antigen that causes an allergic reaction, such as pollen or pet dander

  • pathogen

    a disease-causing organism (virus, bacterium, etc.) that carries antigens; the pathogen is the whole organism, while the antigen is the specific substance that triggers the immune response

Antonyms
  • antibody

    the protein produced by the immune system in response to an antigen; antibodies bind to antigens to neutralise them

Grammar Patterns

antigen + noun (antigen test / antigen reaction)

adjective + antigen (foreign / viral / surface antigen)

Usage Note

Commonly modified by a noun or adjective that identifies the source: flu antigen, pollen antigen, tumour antigen. Distinguish from antibody — an antigen triggers the response; an antibody is the protein produced to fight the antigen.

Common Mistakes

The antigen attacked his lungs.
The antigen triggered an immune response in his lungs.
Antigens do not attack; they cause the immune system to react.
The doctor injected an antigen to cure the disease.
The doctor gave a vaccine containing a weakened antigen to build immunity.
An antigen alone is not a treatment; it is the substance that stimulates the production of antibodies.

Word family

  • antigenic
    adjectiveC1
  • antigenically
    adverbC2
  • antigenicity
    nounC2

Synonym discussion

Sense: noun/1

Antigen is the broadest term: any substance your body treats as foreign, triggering an immune response. An immunogen is a subtype — any antigen that actually provokes a measurable immune response (some small molecules are antigens that bind to antibodies but do not spark a response on their own). An allergen is an antigen that causes an allergic reaction, such as pollen triggering sneezing or itchy eyes. A pathogen is the whole disease-causing organism (a virus, bacterium, or fungus), which carries many antigens on its surface. For everyday health contexts, antigen is the most useful word: when you get a rapid antigen test, it looks for the specific antigen of the virus. Allergen is best for allergy scenarios, and immunogen is mostly used in research or vaccine development discussions.

antigen ↗allergen ↗immunogenpathogen

Common collocations

Nouns

  • antigen test
  • antigen reaction
  • antigen detection
  • antigen presentation

Phrases

  • antigen-antibody reaction
  • surface antigen
  • foreign antigen

Prepositions

  • antigen on
  • antigen in

Etymology

GreekGermanEnglish

Coined in the 1890s from the Greek anti- (against) and -gen (something that produces), modelled on the earlier word toxin. It was first used by German bacteriologist Paul Ehrlich to describe substances that stimulate the body to produce antibodies. The term became widely familiar during the COVID-19 pandemic through rapid antigen testing.