What you need to know
- 6.8Non-specific responses: inflammationA local response to infection or damage: histamine makes blood vessels dilate and become leakier, causing heat, redness and swelling and bringing in phagocytes., lysozymeAn enzyme in tears, saliva and mucus that breaks down bacterial cell walls. action, interferonA protein released by virus-infected cells that inhibits viral replication in nearby cells. and phagocytosisEngulfing a pathogen or particle into a vesicle by endocytosis..
Skin, stomach acid and flora remain 6A 6 (6.7). Antibodies, plasma cells and T killers are 6B 2. This page is the four named processes only.
By the end, you should be able to…
- Name inflammation, lysozyme, interferon and phagocytosis.
- Link histamineA chemical released in inflammation. It dilates arterioles and makes capillaries more permeable. to redness, heat, swelling and extra phagocyteA white blood cell, such as a neutrophil or macrophage, that engulfs and digests pathogens..
- Keep interferon (viral signalling) distinct from lysozyme (bacterial walls).
Build your understanding
After the barrier, before the clone
Non-specific responses act against a wide range of pathogens using the same processes each time. They do not require a lymphocyte clone that fits one antigenA molecule, often a protein or glycoprotein on a cell surface, that the immune system recognises as non-self.. Specification 6.8 names four: inflammationA local response to infection or damage: histamine makes blood vessels dilate and become leakier, causing heat, redness and swelling and bringing in phagocytes., lysozymeAn enzyme in tears, saliva and mucus that breaks down bacterial cell walls. action, interferonA protein released by virus-infected cells that inhibits viral replication in nearby cells. and phagocytosisEngulfing a pathogen or particle into a vesicle by endocytosis.. 6.7 barriers try to stop entry; these four act when tissue is damaged or a cell is already infected.
Do not write plasma cellA cell formed from a B effector cell that secretes large amounts of one antibody. here. antibodyA Y-shaped protein made by plasma cells that binds specifically to one antigen. is specific. Neutrophils and macrophages can phagocytose without a named antigen receptor on a B cell.
Inflammation and phagocytosis
Damaged tissue and mast cells release histamineA chemical released in inflammation. It dilates arterioles and makes capillaries more permeable.. Arterioles dilate and capillaryA tiny vessel whose wall is a single layer of endothelium, giving a short diffusion distance for exchange with tissues. walls become more permeable, so more plasmaThe liquid part of blood: water carrying dissolved substances such as glucose, ions, hormones and proteins. and phagocyteA white blood cell, such as a neutrophil or macrophage, that engulfs and digests pathogens. leave the blood. The tissue looks red, feels hot and swells; pain follows. Those signs are not the purpose — extra phagocytes at the site are.
A phagocyte is attracted chemically, binds the pathogen, engulfs it into a phagosomeThe vesicle that contains a pathogen engulfed by a phagocyte., then a lysosomeA vesicle containing hydrolytic (digestive) enzymes. fuses to make a phagolysosomeThe vesicle formed when a lysosome fuses with a phagosome. Lysosomal enzymes digest the pathogen. and digest the contents. The same cell can repeat this with different microbes. Macrophages that later display antigen are 6.9 antigen-presenting cellA cell, such as a macrophage, that displays a pathogen’s antigens on its surface so that T helper cells can bind.; the engulfing itself is still 6.8.
Lysozyme versus interferon
Lysozyme is an enzymeA globular protein that acts as a biological catalyst, speeding up a specific reaction. in tears, saliva and mucus. It hydrolyses peptidoglycan in bacterial cell wallA rigid layer outside the cell membrane. In plants it is made mainly of cellulose; it supports the cell and resists bursting., so it is an antibacterial chemical barrier at a surface, listed here as a named response. It is not useful against viruses, which have no peptidoglycan.
Virus-infected cells release interferon, a signalling protein. Neighbouring cells reduce viral protein synthesis, which slows spread. Interferon is not an antibody and is not lysozyme. It is a reason a viral infection can be limited before T killers arrive.
Diagram A
NOT: the red swelling is not the purpose. Extra phagocytes at the site are the useful result.
- The same phagocyte can repeat this with different microbes
- No antigen-matched lymphocyte clone is required
- Macrophages that later display antigen are antigen-presenting cells
- Display is the specific response, not this digestion step
- Pain, heat, redness and swelling are the signs, not four extra processes
Two traps this diagram blocks
- Do not call inflammation an antibody response.
- Do not stop at engulfing. Digestion needs the lysosome.
From the diagram alone
Question
Describe how a phagocyte destroys a bacterium after it has arrived at inflamed tissue. [3]
Show a model answer
The phagocyte binds the bacterium and engulfs it into a phagosome. A lysosome fuses with that vesicle. Enzymes in the phagolysosome then digest the bacterium.
Diagram B
NOT: interferon is not an antibody. Lysozyme does not act on viruses.
- Lysozyme is a chemical at a surface, listed with the non-specific responses
- Interferon limits viruses before T killer cells arrive
- Antibodies are specific immunoglobulins from plasma cells
- The two columns are not steps of one pathway
- Peptidoglycan is the bacterial wall polymer from the prokaryote lesson
Two traps this diagram blocks
- Do not call interferon a type of antibody.
- Do not use lysozyme as the defence against a virus.
From the diagram alone
Question
Explain why lysozyme can damage bacteria but not viruses, and state the role of interferon. [4]
Show a model answer
Lysozyme hydrolyses peptidoglycan in bacterial walls. Viruses have no peptidoglycan, so the enzyme does not damage them. Interferon is released by infected cells and causes neighbouring cells to slow viral protein synthesis, which reduces spread.
| Response | What it acts on | Mechanism in one line |
|---|---|---|
| Inflammation | Damaged or infected tissue | Histamine brings plasma and phagocytes |
| Lysozyme | Bacteria at wet surfaces | Hydrolyses peptidoglycan |
| Interferon | Virus-infected neighbourhood | Slows viral protein synthesis |
| Phagocytosis | Many pathogen types | Engulf, then digest in a phagolysosome |
Make your reasoning visible
Name histamine in inflammation
“It goes red” is a sign, not a mechanism.
Lysosome, not lysozyme, inside the phagocyte
lysozymeAn enzyme in tears, saliva and mucus that breaks down bacterial cell walls. is the tear enzymeA globular protein that acts as a biological catalyst, speeding up a specific reaction.. A lysosomeA vesicle containing hydrolytic (digestive) enzymes. fuses with the phagosomeThe vesicle that contains a pathogen engulfed by a phagocyte..
Key explanations
- The tissue is red, hot, swollen and painful because of that extra blood flow and fluid. Those signs are not themselves the defence.
- A lysosome fuses with the phagosome. The combined phagolysosomeThe vesicle formed when a lysosome fuses with a phagosome. Lysosomal enzymes digest the pathogen. digests the contents.
- antigenA molecule, often a protein or glycoprotein on a cell surface, that the immune system recognises as non-self. display by a macrophage comes afterwards and belongs with the specific response.
- Viruses have a capsid, not peptidoglycan, so lysozyme is not an antiviral enzyme.
Avoid this misconception
The claim: interferonA protein released by virus-infected cells that inhibits viral replication in nearby cells. is a type of antibodyA Y-shaped protein made by plasma cells that binds specifically to one antigen. against viruses.
The correction: Interferon is a signalling protein from infected cells. Antibodies are specific immunoglobulins from plasma cellA cell formed from a B effector cell that secretes large amounts of one antibody. (6.9).
Put the non-specific responses in order
Three of the 6.8 non-specific responses are short chains. Each happens the same way whatever the pathogen; none needs a lymphocyte that fits one antigen.
Order the steps
What to do
- Pick a chain with Chain, just below these steps: Inflammation, Phagocytosis or Interferon.
- Reorder the cards below: drag a card (on a touch screen, drag its number), tap a card then tap where it goes, or use the ↑ and ↓ arrows at its right.
- Press Check under the cards to mark each one green (right place) or red; the count shows how many are right.
- Stuck? Hint first outlines the first wrong place, then gives a clue, then places that step for you.
- Shuffle mixes the cards again; Start again returns them to the starting order. Keyboard: Space picks up, arrow keys move, Space drops.
Tissue is damaged. Put the steps of inflammation in order.
0 of 6 in the right place
Lysozyme, the fourth 6.8 response, is a single step (it hydrolyses bacterial cell walls), so it is not ordered here. Real inflammation involves more signals than histamine.
Check your understanding
Try each question before opening the suggested answer.
Check your understanding (continued)
Practice question
Retrieval and explanation · suggested answer
List the four non-specific responses named in 6.8.
Show suggested answer
Inflammation, lysozyme action, interferon and phagocytosis.
Practice question
Retrieval and explanation · suggested answer
Describe how inflammation develops after tissue damage.
Show suggested answer
Histamine is released; arterioles dilate and capillaries become more permeable; more phagocytes and plasma reach the tissue, causing redness, heat, swelling and pain.
Practice question
Retrieval and explanation · suggested answer
Where is lysozyme found and what does it do?
Show suggested answer
In tears, saliva and mucus. It hydrolyses peptidoglycan in bacterial cell walls.
Practice question
Retrieval and explanation · suggested answer
Outline phagocytosis in order.
Show suggested answer
The phagocyte is attracted and binds the pathogen, engulfs it in a phagosome, a lysosome fuses to form a phagolysosome, and the pathogen is digested.
Take the idea further
Apply the same specification knowledge to an unfamiliar problem. Any extra assumptions are supplied in the question.
Stretch question
A student writes that interferon “dissolves bacterial walls like lysozyme, then antibodies finish the job”. Rewrite using only 6.8, then say which later point covers antibodies.
Show a hint
Virus versus bacterium; specific versus not.
Explore the reasoning
Interferon is released by virus-infected cells and reduces viral protein synthesis in neighbours; lysozyme hydrolyses bacterial peptidoglycan. Neither is an antibody. Antibodies are 6.9, secreted by plasma cells after clonal selection.
Recall this lesson
Lesson recall questions
Question 1 of 5: Describe, in order, how inflammation develops after tissue damage.
Non-specific responses
Practice question
Retrieval and explanation · suggested answer
Describe, in order, how inflammation develops after tissue damage.
Lesson: 6B 1: Non-specific Responses to Infection
Build the sequence from memory first. Then reveal the model order.
Tap the steps in the order you recall. Tap a placed step to send it back.
- 01Next step
- 02Waiting
- 03Waiting
Tap to place
Put your biology to work
Explore where these ideas appear in the world. Enrichment, not extra required recall.
NIAID’s innate layer is this page in other words
6B · Non-specific Responses to InfectionNIAID describes innate immunity as fast, broad defences that do not remember one antigen the way lymphocytes do. Inflammation and phagocytosis sit in that layer. Their overview is…Specification 6.8Read & use the scienceClose article
Why this matters
NIAID describes innate immunity as fast, broad defences that do not remember one antigen the way lymphocytes do. Inflammation and phagocytosis sit in that layer. Their overview is enrichment, not extra named cells. Stay with the four specification processes in an exam answer. A broad response can start before the body has selected a clone of lymphocytes. Interferon is a signal to neighbouring cells rather than an antibody made by plasma cells, so it belongs with this early defence.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 4, pp. 29–32. The application extends beyond required recall.
- 6.8 understand the non-specific responses of the body to infection, including inflammation, lysozyme action, interferon and phagocytosis
Use the science
Why is “the body remembers the bacterium so inflammation is stronger the second time” the wrong 6.8 claim?
Explore a possible response
Memory belongs to lymphocytes (6.10). Inflammation and phagocytosis can happen on a first meeting; they are not a secondary antibody response.
Explore the source
A warning message to neighbouring cells
6B · Non-specific Responses to InfectionInterferons are signalling proteins released during some viral infections. A scientific review describes how neighbouring cells respond by activating antiviral genes, making viral spread harder. That is a…Specification 6.8Read & use the scienceClose article
Why this matters
Interferons are signalling proteins released during some viral infections. A scientific review describes how neighbouring cells respond by activating antiviral genes, making viral spread harder. That is a non-specific early response: the signal does not need to recognise one named virus in the way an antibody binds a matching antigen. It also does not guarantee that infection stops, because viruses can interfere with host defences and the response varies among tissues. The school specification lists interferon alongside inflammation, lysozyme and phagocytosis. These mechanisms cooperate but are not interchangeable: a phagocyte engulfs material, while an interferon changes cellular behaviour.
Back to the specification
Pearson Edexcel IAL Biology · Issue 2, February 2021 · Unit 4, pp. 29–32. The application extends beyond required recall.
- 6.8 understand the non-specific responses of the body to infection, including inflammation, lysozyme action, interferon and phagocytosis
Use the science
Why is interferon signalling a different defence from a plasma cell secreting a virus-specific antibody?
Explore a possible response
Interferon induces a broad antiviral state in responding cells; a plasma-cell antibody binds a particular antigen and belongs to adaptive immunity.
Explore the source
- Regulation of type I interferon responsesNature Reviews Immunology · Abstract