Immunity to pathogens

Question 1

How does infection by pathogens cause disease?

Answer 1

Either by host cell death or toxin production

Question 2

List some of the receptors involved in the innate immune response

Answer 2

• TLR
• N-formyl-methionyl receptor
• Mannose receptor

Question 3

What do T1 cells trigger?

Answer 3

IFN-y and TNF

Results in CMI triggered due to macrophage activation

Question 4

What do Th2 cells do?

Answer 4

Secrete IL-10, IL-4 and IL-5 which both inhibit microbicidal function of macrophages and promotes mast cells, eosinophils and IgE

Question 5

What triggers macrophages?

Answer 5

IFN-y

Question 6

What is the main cause of tissue damage in intracellular bacterial infections?

Answer 6

The hosts delayed type hypersensitivity response

Question 7

Describe cell mediated immunity

Answer 7

• Adaptive

- T cells activate phagocytes to eliminate microbes

Question 8

How do extracellular bacteria evade the IR?

Answer 8

• Inhibit the complement system (alternative pathway)
• Resistance to phagocytosis
• Antigenic variation in surface antigens

Question 9

How do intracellular bacteria evade the IR?

Answer 9

• Inhibit phago-lysosome fusion

- Escape to cytosol

Question 10

Describe innate immunity to viruses

Answer 10

• Infected tissue produced type 1 IFNs. Induced by TLR recognition of viral DNA/ RNA
• NK cells: active where virus inhibits MHC 1 CTL responses
• Apoptosis: mediated by host PKR kinase which inhibits protein synthesis in cells.

Question 11

Describe adaptive immunity to viruses

Answer 11

• Neutralising antibody (prevents virus entry (IgA), removed free virus)
• CTL: MHC 1 restrictied killing of infected host cells
• Ab and complement mediated opsonisation for phagocytosis

Question 12

Describe adaptive immunity to viruses

Answer 12

• Neutralising antibody (prevents virus entry (IgA), removed free virus)
• CTL: MHC 1 restrictied killing of infected host cells
• Ab and complement mediated opsonisation for phagocytosis

Question 13

Which steps of immunity to virus provide protection against infection?

Answer 13

• Adaptive: neutralising antibody

- Innate: Type 1 IFN production puts tissue into antiviral state

Question 14

Which steps of immunity against viruses provide eradication of the infection?

Answer 14

• Adaptive: CTL response

- Innate: NK cell response

Question 15

Describe the two ways CTLs cause apoptosis of a cell

Answer 15

1) Granule exocytosis. Enter cell by perforin dependant mechanisms- triggers apoptosis pathway
2) FasL-Fas mediated, FasL on CTL interacts with Fas on target cell

Question 16

How do viruses evade the IR?

Answer 16

• Inhibit antigen presentation (decoy MHC molecules, inhibit MHC synthesis, inhibit proteosomal activity)
• Inhibit apoptosis
• Inhibit interferons (Inhibit IFN signalling pathway, decoy receptors)
• Antigen variation
• Latency

Question 17

Name an endoparasite which is often resistant to phagocytes and complement

Answer 17

-Helminths (have thick teguments)

Question 18

How do the immune response deal with helminths?

Answer 18

• Th2 mediated

- IgE, mast cells, eosinophils

Question 19

How does the immune response deal with protozoal infections?

Answer 19

Those captured by macrophages= Th1 CMI/ macrophage activation
-CTL killing of infected cells