[W9] Immune responses to infection

Question 1

What four factors shape the immune response to infection?

Answer 1

Route of infection, systemic vs local, intracellular vs extracellular, and APC/T cell signalling pathways.

Question 2

What determines whether cellular or humoral immunity dominates?

Answer 2

Whether the pathogen is intracellular (→ cellular immunity) or extracellular (→ humoral immunity).

Question 3

Which TLR recognises LPS from Gram-negative bacteria?

Answer 3

TLR4 (CD284)

Question 4

What does TLR2 recognise?

Answer 4

Peptidoglycan from Gram-positive bacteria and helminths.

Question 5

What TLR detects dsRNA from viruses?

Answer 5

TLR3

Question 6

Which TLRs detect CpG DNA and ssRNA?

Answer 6

TLR9 (CpG DNA) and TLR7 (ssRNA)

Question 7

What cytokines do Th1 cells produce and what do they fight?

Answer 7

IFN-γ, IL-2, TNF-α – fight intracellular pathogens.

Question 8

What is the role of Th2 cells?

Answer 8

Secrete IL-4, IL-5, IL-13 to combat helminths, activate eosinophils and mast cells.

Question 9

What do Th17 cells recruit?

Answer 9

Neutrophils – important against extracellular bacteria.

Question 10

What is the role of Treg cells?

Answer 10

Produce TGF-β to suppress immune responses and promote tolerance.

Question 11

What is the main function of IgG?

Answer 11

Systemic protection, opsonisation, and complement activation.

Question 12

Where is IgA most effective?

Answer 12

Mucosal surfaces – blocks pathogens in the gut and lungs.

Question 13

What is IgE involved in?

Answer 13

Anti-helminth responses and allergic reactions.

Question 14

What is the first antibody produced in infections?

Answer 14

IgM

Question 15

How is influenza virus detected by the immune system?

Answer 15

TLR3 detects viral dsRNA.

Question 16

What is the main innate cytokine response to influenza?

Answer 16

Type I interferons (IFN-α and IFN-β)

Question 17

How do CD8+ T cells help against influenza?

Answer 17

Kill infected cells and produce IFN-γ to enhance MHC I expression.

Question 18

What do antibodies target on the influenza virus?

Answer 18

Haemagglutinin and neuraminidase

Question 19

What TLRs are involved in detecting Salmonella?

Answer 19

TLR4 (LPS), TLR5 (flagellin), TLR9 (CpG DNA)

Question 20

Which antibody is most important in the gut against Salmonella?

Answer 20

IgA

Question 21

How do NK cells respond to opsonised Salmonella?

Answer 21

Use FcγRIII (CD16) to kill infected cells.

Question 22

What T cell response is activated against Salmonella?

Answer 22

Th1 response – IFN-γ activates macrophages.

Question 23

How does Schistosoma enter the body?

Answer 23

Penetrates skin and migrates to the liver.

Question 24

What T helper response is needed for helminths?

Answer 24

Th2 response

Question 25

What role does IgE play in helminth immunity?

Answer 25

Binds to mast cells and eosinophils to mediate attack.

Question 26

What is the pathological consequence of Schistosoma eggs in the liver?

Answer 26

Granuloma formation, fibrosis, and hepatomegaly.

Question 27

What is immunopathology?

Answer 27

Damage caused by an overactive or misdirected immune response.

Question 28

Why is regulation of the immune response important?

Answer 28

To ensure effective clearance without causing tissue damage.

Question 29

What factors determine the immune response to infection?

Answer 29

Pathogen type, TLRs triggered, APCs involved, cytokine signals, T cell subsets activated, antibody isotype used.

Question 30

Is there a single immune response for all infections?

Answer 30

No – responses are context-dependent and tailored to each pathogen.