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Immunobiology > Lecture 1 - Overview of the Immune System > Flashcards

Lecture 1 - Overview of the Immune System Flashcards

1
Q

What is the purpose of the Immune System?

A

The Immune System serves to prevent and control infections with pathogenic microbes

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2
Q

Where did the field of Immunology originate?

A

Edward Jenner discovered that Cowpox protected against Human small pol infection in 1796.

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3
Q

In what year was smallpox officially eradicated?

A

Smallpox was officially eradicated in 1979.

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4
Q

What are the four classes of pathogens?

A

Extracellular bacteria, parasites and fungi

Intracellular bacteria and parasites

Viruses (intracellular)

Parasitic Worms (extracellular)

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5
Q

What are the four different types of barrier in innate immunity?

A

Physical/anatomical
Physiological
Phagocytic
Inflammatory

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6
Q

What are the core components of innate immunity?

A

Phagocytic cells - engulf bacteria and kills virally infected cells and parasites.

Serum proteins - eg. complement, tag foreign bodies and can attack organisms.

Cytokines - interact and activated other cells.

Inflammation - the overall aim of the innate response.

NK cells - a type of lymphocyte.

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7
Q

What are the characteristics of Innate Immunity?

A

It is present from birth.
It is non-specific.
It does not develop after subsequent exposures, the response is not amplified.
Some mechanisms are evolutionarily very conserved.
It is present in lower animals.

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8
Q

Does an increased innate response occur for subsequent infections?

A

No, the innate immune response does not develop. Any subsequent exposure will trigger an identical response.

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9
Q

What are the lungs and digestive tract lined with?

A

Lungs - Cilia and Mucus

Stomach - Mucus and Acid

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10
Q

What barriers prevent the entry of microorganisms?

A

Skin, mucous membranes, stomach acid, gut flora (good bacteria)

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11
Q

Describe the defence within the gut against invader organisms.

A

There are various secretions, sebum, low pH, symbionts/commensals (good bacteria) which out compete bad bacteria and aim to defeat them. There is a flow of mucus which has two layers, a more and less viscous layer. The cilia try to propel the invaders away that get stuck in the viscous layer.

If they get through into the tissue there is the complement defence which can bind the bacteria and also macrophages which can engulf the bacteria.

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12
Q

Briefly describe phagocytosis.

A

Various cells types (mainly macrophages and neutrophils) are able to engulf, phagocytose invader molecules.

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13
Q

What is the overall aim of inflammation?

A

Inflammation is a complex series of events that results in the recruitment of more cells to the infected or damaged area.

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14
Q

How does the body recognise non-self or ‘danger’?

A

The body has a series of receptors on its own cell surfaces which can detect other molecules passing them.

On non-self molecules there are foreign flags which can be detected. There is then a ligand interaction between the receptor and the foreign flag.

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15
Q

How do phagocytes engulf and kill?

A

Phagocytes engulf and kill by proteolytic degradation and the release of oxygen radicals.

A bacterium is recognised by the phagocyte, engulfed forming a phagosome, the bacterium is then degraded.

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16
Q

What receptors are present on the phagocyte that recognise antigens?

A

Fc receptors bind antibody coated bacteria and can trigger phagocytosis.

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17
Q

Describe the process of phagocytosis of a bacterium.

A

The binding of aggregated antibody molecules to Fc receptors on the phagocyte causes the cell to engulf the bacterium.

The phagocyte first produces pseudopods, or ruffles that surround the bacterium and then fuse. The bacterium is then trapped in what is now an intracellular vesicle - the phagosome.

Within the phagocyte, lysosomes fuse with the phagosome delivering their enzymatic contents to degrade the engulfed bacterium.

18
Q

What cells are the first line of defence in recognising pathogens?

A

Macrophages and Dendritic cells.

19
Q

What are PAMPs?

A

Pathogen-associated molecular patterns.

20
Q

What are Toll-like Receptors?

A

Toll-like Receptors or TLRs are composed of multiple leucine rich repeats which are useful for recognising various PAMPs.

TLRs are membrane associated proteins, some are located on the surface of the cell, whilst others are located on endocytic vesicles where they survey the degraded components of pathogens taken up through endocytosis.

Each member of the TLR family recognises different types of PAMPs.

21
Q

What type of PAMP does TLR 5 recognise?

A

TLR5 recognises flagellin. This is a highly conserved constituent of the bacterium flagellum.

22
Q

What type of PAMP does TLR9 recognise?

A

TLR9 recognises methylated CPG oligonucleotide motifs which are contained within the bacterial genome once the genome has been degraded within the lysosome.

23
Q

What PAMP does TLR6 and TLR2 recognise?

A

TLR6 and TLR2 are a dimer that recognises diacyllipopetides.

24
Q

What PAMP do TLR1 and TLR2 recognise?

A

TLR1 and TLR2 are a dimer that recognise triacyllipopetides.

25
Q

What PAMP does TLR4 recognise?

A

TLR4 recognises lipopolysaccharides (LPS) a component of Gram negative bacteria.

26
Q

What PAMPs do TLR3 and TLR7 recognise?

A

TLR3 and TLR7 are located on endocytic vesicles and recognise double stranded RNA and single stranded RNA respectively.

27
Q

What occurs when a TLR is activated?

A

When a TLR is activated it sends a signal to the nucleus by activating transcription factors.

28
Q

Where do viruses exist and replicate?

A

Viruses exist and replicate in the cytosol.

29
Q

What classes of receptors can detect pathogens in the cytosol?

A

One class of such receptors are members of the Nuclear Oligomerisation Domain, or NOD proteins.

A class of intracellular receptor proteins that contain an RNA helicase domain and two caspase recruitment domains. A member of this family is RIG-I.

30
Q

Describe NOD2

A

NOD2 is located in the cytosol can detect bacterial proteoglycans of intracellular bacteria. When the NOD protein recognises its ligand, the muramyl dipeptide, it sends a signal to the nucleus to activate transcription.

31
Q

Describe RIG-I

A

RIG-I is an intracellular receptor protein. It recognises double stranded RNAs that are component in the lifecycle of many RNA viruses.

This sends a signal to the nucleus which triggers the production of type 1 interferons.

32
Q

What ability do the TLRs, NOD proteins and the RNA helicase CAR domain family provide the innate immune system with?

A

The ability to detect both extracellular and intracellular pathogens and to activate an immune response against them.

33
Q

Describe some of the receptors that are present on a macrophage,

A 
Mannose receptor
LPS receptors
Glucan receptor
TLR-4
Scavenger receptor
34
Q

What happens when a cell recognises non-self or danger?

A

The bacteria is recognised by surface receptor.
Surface receptors are upregulated.
The resting phagocyte is activated.
The cell is activated.

35
Q

What types of cytokines can be released by an activated macrophage?

A 
IL-1β
TNF-α
IL-^
CXCL8
IL-12
36
Q

What effects does the cytokine IL-1β cause?

A 
IL-1β activates vascular endothelium. 
Activates lymphocytes. 
Local tissue destruction.
Increases access of effector cells.
Triggers fever and the production of IL-6
37
Q

What effects does the cytokine TNF-α cause?

A

TNF-α activates the vascular endothelium and increases vascular permeability, which leads to increased entry of IgG, complement, and cells to tissues and increased fluid drainage to lymph nodes.

This results in fever, mobilisation of metabolites and shock.

38
Q

What effects does the cytokine IL-6 cause?

A

IL-6 results in lymphocyte activation and increased antibody production.

This causes fever and induces acute-phase protein production.

39
Q

What effects does the cytokine CXCL8 cause?

A

CXCL8 results in chemotactic factor recruiting neutrophils, basophils and T cells to the site of infection.

40
Q

What effects does the cytokine IL-12 cause?

A

IL-12 activates NK cells. Induces the differentiation of CD4 T cells into TH1 cells.

41
Q

.

A

slide 24

Immunobiology (3 decks)

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