CIE A Level Biology (9700) 2019-2021

Revision Notes

11.1.4 Antigens

Antigens, Self & Non-Self

  • Every cell in the human body has markers that identify it
  • Microorganisms (both pathogenic and non-pathogenic), such as bacteria and viruses, also have their own unique markers
  • These markers are called antigens (which are macromolecules) and they allow cell-to-cell recognition
  • Antigens are found on cell surface membranes, bacterial cell walls, or the surfaces of viruses
    • Some glycolipids and glycoproteins on the outer surface of cell surface membranes act as antigens
  • Antigens can be either self antigens or non-self antigens:
    • Antigens produced by the organism’s own body cells (those that the immune system does not recognise as foreign antigens) are known as self antigens
    • Self antigens do not stimulate an immune response
    • Antigens not produced by the organism’s own body cells (those that the immune system recognises as being foreign eg. the antigens found on pathogenic bacteria and viruses or if a person receives a different blood type during a transfusion) are known as non-self antigens
    • Non-self antigens stimulate an immune response


Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.

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