Antigen
A foreign molecule, often on a pathogen's surface, that triggers an immune response.
In other languages
- EN: Antigen
- BM: Antigen
- 中文: 抗原
In the syllabus and the exam
Antigen sits at the start of the immune response chain in the content standard and is usually paired with antibody in exam items that test whether candidates understand which molecule triggers a response and which molecule is produced in response. Candidates should be able to state that an antigen is typically a protein found on the surface of a pathogen, a transplanted cell, or even pollen, and that its recognition as foreign by white blood cells is what starts antibody production. A common structured question describes a first and a second exposure to the same pathogen and asks candidates to explain why the second immune response is faster, expecting an answer built around memory cells recognising the antigen more quickly the second time. The most frequent factual error is swapping the roles of antigen and antibody, describing the antigen as something the body produces rather than the foreign trigger the body responds to.
Example
The influenza virus displays antigens on its surface that the immune system recognises as foreign each flu season.
Related terms
Source:SRC-DSKP-EN
Related
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