Microbiology/Immunology

Question 1

LO: understand that deficiencies or excess activation of the innate system can occur and result in various health outcomes

Answer 1

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Question 2

LO: understand the impact of pro-inflammatory cytokines IL-1, TNF and IL-6

Answer 2

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Question 3

LO: Understand that ligation of particular PRRs are associated with the formation of large multi-molecular complexes that regulate the production of IL-1 and IL-18
How does this occur?

Answer 3

• binding of pattern recognition receptors such as NOD like receptors
• triggers a cascade of protein reactions
• results in the formation of a large congregation of proteins: the inflammasome which
• cleaves (or leads to autolytic cleavage?) or inactive caspase 1 to active caspase 1 which
• cleaves inactive IL-1 (and IL-18?) to its active form

Question 4

LO: understand the key process of how these complexes are formed and generate the proinflammatory response

Answer 4

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Question 5

LO: Understand the concept of pyroptosis and how this contributes to inflammation and infection control
What is pyroptosis?

Answer 5

It is the death of a cell due to inflammasome formation. The IL-1 and inflammasome leave the cell, and the latter can be taken up by other cells.

Question 6

LO: Understand that many disease states are related to excess IL-1 and increased inflammasome activation

Answer 6

Eg. Familiar cold urticaria,

Question 7

LO: understand that some previously understood inflammatory disorders are now associated with defects in NLRP3

Answer 7

Eg. familial cold urticaria

Question 8

LO: understand the role of IL-1 as a potential therapeutic target.

Answer 8

IL 1 changes the metabolism in such a way that it promotes metabolic syndrome. Chronic inflammatory disease is bad!
Does this by promoting insulin resistance (more insulin is required to bring sugar into the cells). Causes hyper-insulin, which increases insulin demand. Eventually get insulin deficiency as the pancreas becomes exhausted/ beta cells die.

Question 9

What are the cardinal signs of acute inflammation?

Answer 9

1. Heat
2. Redness
3. swelling
4. pain
5. loss of function

Question 10

What are the steps in acute injury/the innate response?

Answer 10

Vascular and cellular (overlapping stages):
• Brief vasoconstriction then
• Vasodilation/congestion, incr permeability
• Reduced flow velocity (increased viscosity as fluid leaves the capillaries), clotting
• extravasation of WBC which migrate due to chemotaxis
• Phagocytosis of debris, thus exudates (swelling and pain)
• Mediator action mediates response, derived from cells or plasma:
○ Histamine (cell derived, MC in Conn tissue next to blood vessels, basophils in blood)- vasodilation and incr perm
○ Serotonin has a similar function
○ 3 major plasma derived protein mediators
§ Kinins promote pain/inflam
§ Clotting cascade trap bugs and mediates haemostasis
§ Complement: promotes inflam and phagocytosis

Question 11

What does the word interleukin mean? What is the main one driving acute inflammation?

Answer 11

A protein produced by leukocytes (which mediates action b/t them). IL1.

Question 12

What are the pro inflammatory actions of IL1?

Answer 12

Pleiotropic!
Focus is endogenous pyrogen, leukocyte mediator and lymphocyte activation

Metabolic
Physiologic (hypothalamus- fever)
Inflammatory
Haematologic (BM- neutrophilia, incr phagocytosis and IL6, decr erythropoeisis)
Immunologic (acts on B and T cells)

Question 13

What is the structure of IL1?

Answer 13

Formed as a large biologically inactive protein (IL-1 beta precursor 31kDa- #s not mentioned!).
Is enzymatically cleaved by ICE (interleukin 1 converting enzyme= caspase 1) removing the N terminus (not imp?) end to form active IL-1 beta (18kDa)

Question 14

What is familial cold urticaria?

Answer 14

Rare genetic disease- single nucleotide mutation of cryopyrin (=NLRP3) gene, a member of the Nod like receptor family.
Is associated with interleukin 1 converting enzyme. In this disease the enzyme is over active, increased IL-1 production.
Signs of acute inflammation when exposed to cold.

Question 15

What are nod like receptors? (NLRs)

Answer 15

Lots being discovered, they’re molecules associated with the formation of inflammasomes and thus activation of IL-1 (and other cytokines?) converting enzyme.

Question 16

What is gout and how can gout be treated with IL-1 receptor antagonists (name?)?
What other conditions can be?
Contraindications?

Answer 16

Gout is a painful, acute inflammation of the joint caused by the precipitation of mono-sodium urate crystals in joints. The chronic sequelae is tophi. 
MSU builds up if there is dietary excess (e.g. purine rich foods such as red meat of which t is a break down product) and or if there is reduced renal function, such that the renal clearance capacity is exceeded. 
These crystals (as well as others e.g. asbestos, alum- in vacs, cholesterol) active Nod like receptors and cause inflammasome formation/IL1 production. Does it need a second signal? Anakinra- Antagonising the IL1 produced blocks the acute inflammation and thus pain associated. 
Also useful for rheumatoid, osteoarthritis. DM. 
Contrindication: neutropenia (because inhibiting acute inflame response, don't want to cripple it/leave open to infection)

Question 17

How is IL1 production controlled to prevent unnecessary inflammation?

Answer 17

Requires 2 signals to converge on the SAME cell.

1. Priming: binding of TLRs or endogenous cytokine receptors initiates transcription of pro-IL-1-b.
2. Binding of Nod like receptors by infectious particles (candida, back/viral rna, influenza protein, cholera or pore forming toxins) induces the formation of the inflammasome.

Question 18

How does Salmonella avoid the immune system?

Answer 18

Forms long living vacuoles in macrophages. Also down regulates flagellun, which is an inflammasome activator via NOD like receptor binding.

Question 19

What are the two mechanisms by which inflammasomes assist in Salmonella clearance? (the reason why care is needed with Ankinra use)

Answer 19

1. If flagellun is sensed, there in inflammasome formation thus the cell lyses (pyroptosis) and bacteria are cleared by neutrophils.
2. When dendritic cells are infected, in addition to lyse/release above, get cleavage of pro IL-18 to IL-18 by caspase 1, which activates (CD8+) T cells and thus assists clearing of intracellular pathogens (such as Salmonella)

Question 20

What is metabolic syndrome?

What can it lead to/be associate with?

Answer 20

3 of the following: obesity, hypertension, dyslipidaemias, high glucose.
Characterised by obesity, insulin resistance (DM) and deposits in vessel walls (hypertension, CVD, stroke).
Can lead to cancer, dementia, polycystic ovary disease, non alcoholic fatty liver disease

Question 21

What is the role of inflammasomes with metabolic syndrome?

Answer 21

Precipitation of fat metabolites (like gout) Crystal formation with dyslipidaemias.
(? lipid derived mediators released with death of adipocytes, which can form crystals).
This leads to low grade chronic inflammasone/IL-1 production (by macrophages which are sitting in the adipose tissue).

Question 22

What is the role of IL-1 beta in metabolic syndrome?

Answer 22

Acts on cells such as adipocytes and hepatocytes to decrease their sensitivity to insulin, resulting in increased BG and development of type II diabetes due to insulin resistance (pancreas tries to make more, becomes exhausted, beta cell death).
High BG impairs protein function and exacerbates everything.
There are also cholesterol deposits in the intima of vessels causing atherosclerosis→ cholesterol clefts/precipitates → activates inflammasomes in macrophages → perpetuates chronic inflammation underlying atherosclerosis, narrowing of vessels which can lead to infarction in the heart, stroke in the brain.