3.1.10

Human Defence Systems - Immune Systems

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The Immune System

If a pathogen passes the non-specific defences, the immune system is activated. The immune system is made up of different white blood cells, which have different functions.

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Phagocytosis

  • A white blood cell finds the pathogen and engulfs it by changing shape.
  • The white blood cell ingests (absorbs) and digests the pathogen, destroying it.
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Antibodies

  • White blood cells recognise foreign antigens (proteins) on the surface of pathogens and produce protein molecules called antibodies.
  • Antibodies are specific to particular pathogens.
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Antitoxins

  • Some bacteria produce toxins that can damage cells and tissues.
  • The immune system responds to this by producing antitoxins, which neutralise the toxins released by the bacteria and prevent them from causing harm.

Jump to other topics

1Cell Biology

1.1What's in Cells?

1.2Cell Division

1.3Transport in Cells

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

5.1Homeostasis

5.2The Human Nervous System

5.3Hormonal Coordination in Humans

5.4Plant Hormones

6Inheritance, Variation & Evolution

7Ecology

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