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
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Two Kinds of Response
Non-specific
- Non-specific The same response occurs whatever the pathogen, and it begins immediately after infection.
Specific
- Specific The response is directed at a particular pathogen by recognising its antigens.
Antigens
- Antigens Antigens are molecules, usually proteins or glycoproteins, on cell surfaces that identify cells as self or non-self.
Non-self
- Non-self Antigens of pathogens are non-self, so the immune system recognises them as foreign.
After the barriers
- 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
- Mast cells Damaged tissue stimulates mast cells to release histamine, a signalling molecule.
Vasodilation
- Vasodilation Histamine widens blood vessels and makes capillary walls more permeable, so fluid enters the tissue and causes swelling.
Cytokines
- Cytokines Cells also release cytokines that attract phagocytes to the site of infection.
Interferons
- Interferons Virus-infected cells release interferons, which prevent viral protein production and warn neighbouring cells.
Fever
- 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
- Speed Non-specific responses start within minutes, long before the specific response has built up.
Link
- Link Antigen presentation connects the non-specific response to the specific immune response.
Sign of infection
- Sign of infection Swelling, warmth and pain at a wound show that inflammation is under way.
Viruses
- Viruses Interferons are especially important in slowing the spread of viral infection.
Macrophages
- 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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