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6.2.3Unit 6: Practical Skills in Biology II

Non-Specific Immune Responses — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 5 parts Lesson 9 of 48 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
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Part 1 of 5Two Kinds of Response

6.2.3 Non-Specific Immune Responses
Non-specific
  • The same response occurs whatever the pathogen, and it begins immediately after infection.
Specific
  • The response is directed at a particular pathogen by recognising its antigens.
Antigens
  • Antigens are molecules, usually proteins or glycoproteins, on cell surfaces that identify cells as self or non-self.
Non-self
  • Antigens of pathogens are non-self, so the immune system recognises them as foreign.
After the barriers
  • Barriers stop most pathogens, and the non-specific responses deal quickly with those that get through.

Part 2 of 5Inflammation and Interferons

These three responses start within minutes of tissue damage or infection.

Inflammation and Interferons
Mast cells
  • Damaged tissue stimulates mast cells to release histamine, a signalling molecule.
Vasodilation
  • Histamine widens blood vessels and makes capillary walls more permeable, so fluid enters the tissue and causes swelling.
Cytokines
  • Cells also release cytokines that attract phagocytes to the site of infection.
Interferons
  • Virus-infected cells release interferons, which prevent viral protein production and warn neighbouring cells.
Fever
  • Cytokines can also raise body temperature, and a fever slows the growth of some pathogens.

Part 3 of 5Phagocytosis

The sequence below shows how a phagocyte deals with a bacterium.

1
Chemicals from pathogens and from damaged cells attract phagocytes, which move out of capillaries into the tissue.
2
The phagocyte recognises the pathogen as non-self and its membrane extends around it.
3
The pathogen is enclosed in a phagocytic vacuole by endocytosis.
4
Lysosomes fuse with the vacuole and release enzymes, including lysozyme, which digest the pathogen.
5
The phagocyte displays pathogen antigens on its surface, becoming an antigen-presenting cell that starts the specific response.

Part 4 of 5Why It Matters

Speed
  • Non-specific responses start within minutes, long before the specific response has built up.
Link
  • Antigen presentation connects the non-specific response to the specific immune response.
Sign of infection
  • Swelling, warmth and pain at a wound show that inflammation is under way.
Viruses
  • Interferons are especially important in slowing the spread of viral infection.
Macrophages
  • Macrophages are large phagocytes that carry out phagocytosis and then act as antigen-presenting cells.

Part 5 of 5Exam Checklist & Tips

6.2.3 – Key Points for the Exam

  • Antigen A molecule on a cell surface that can trigger an immune response.
  • Histamine A chemical released by mast cells that causes inflammation.
  • Phagocytosis Engulfing and digesting of pathogens by phagocytes.
  • Interferon A protein released by virus-infected cells that reduces viral replication.
  • Cytokine A cell signalling molecule that helps to coordinate the immune response.

Common Mistakes

  • Writing that phagocytes make antibodies; antibodies are made by plasma cells.
  • Missing the step in which lysosomes fuse with the vacuole to digest the pathogen.
  • Saying that inflammation is caused by the pathogen itself, rather than by histamine from mast cells.
  • Describing the non-specific response as slow; it begins immediately.

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