Immune System 1:

Question 1

What are the mucosal parts?

Answer 1

The mucosal bots of our body are the main entry points for pathogens. They include stuff like our respiratory system our glands and our urinary and intestinal tracts

Question 2

What is the first layer of protection against pathogens

Answer 2

Our skin is the first thing of protection. Most pathogens cannot pass the skin, this is why the majority of pathogens will infect us via our mucus

Question 3

Describe the four different mechanical barriers

Answer 3

Across our skin intestine lungs as well as eyes nose mouth, we have epithelium cells that prevent pathogens from crossing inside.
In the intestine, peristaltism helps remove the bacteria just by pushing them through the system.
In the lungs, a similar thing happens with the movement of the cilia pushing bacteria outside the bronchi.
Tears and cilia also play an important role in reducing infections

Question 4

Describe a few chemical barriers protecting us against pathogens

Answer 4

Fatty acids on our skin
Acidic acid low ph
Digestive enzymes
Surfactant in our lungs
Enzymes in our tears and our saliva

Question 5

Provide an example of the microbiological barrier that protects us against pathogens

Answer 5

One great example of this is the microbiome.
The diversity in the microbiote serves to teach our immune system how to react to different pathogens.

Question 6

Why does a breach in microbiote can lead to infection

Answer 6

Because the perturbation of the normal flora can allow bacteria to easily access food that otherwise would be taken up by our normal bacteria. In addition our immune system is weakened

Question 7

Give an example of how a breach in the mechanical barrier can lead to an infection

Answer 7

In terms of the skin, of reach in the epithelial layer makes us vulnerable to a cellulitis
In cystic fibrosis there is an issue with the cilia which makes it more difficult to move mucus outside of the lungs making it more likely for these patients to get an infection because the bacteria stays there.

Question 8

Give an example of how a breach in the chemical barrier can lead to an infection

Answer 8

Let’s say that we have a patient that has terrible acid reflux.
If the patient is taking proton pump inhibitors they would increase the gastric ph which would favor the infections from Clostridioides difficile as well as salmonella. This is because the reduced stomach acidity increases the rate of survival of bacteria

Question 9

Describe an example of how a breach in the microbiological barrier can lead to an infection

Answer 9

A patient that takes antibiotics could potentially perturbate her natural flora which could allow Clostridioides difficile to proliferate and cause an infection.
Another example are antibiotics that perturb the vaginal flora leading to fungal infections

Question 10

What is the first attacker of the pathogen once the p[athogen has passed the first three layers of protection

Answer 10

The complement system

Question 11

What is the main role of the complement system in the innate immune system?

Answer 11

The first role is the detection of a pathogen that leads to an activation cascade

Question 12

Describe the three consequences of the activation of the complement system cascade

Answer 12

1 production of pro inflammatory cytokines
2 sticking of the complement proteins on the surface of the pathogen which lead to the lysis of the pathogen via the formation of a membrane attack complex
3 the proteins activated by the complement will be sticking to the surface of the pathogen favoring its phagocytosis (opsonisation)

Question 13

What do the cytokines release by the complement system do?

Answer 13

Let’s say cause a vasodilation of the blood vessels increasing permeability which leads to the recruitment of other immune cells.
The cytokines released by the complement immune system are essentially a messenger for the cells in the near environment

Question 14

Describe what are cytokines

Answer 14

Cytokines are a way of communication between different cells.
They can message for proliferation differentiation activation vasodilation molecule synthesis or even fever. For example some cytokines can travel to the brain and trigger an increase in temperature in the hypothalamus.
Cytokines can be autocrine paracrine or endocrine

Question 15

Describe the membrane attack complex

Answer 15

The membrane attack complex is created from the complement system
What happens here is that the complements will stick to the surface of the pathogen and start creating small holes in the membrane
These holes essentially mean that the bacteria will die

Question 16

Describe how the complement system helps with Opsonisation

Answer 16

Macrophages have certain receptors for compliments and so when the complement bind to the pathogen it is easier for macrophages to recognize the pathogen and opsonize it

Question 17

What is the origin of macrophages, neutrophils, natural killer cells

Answer 17

All immune cells will come from bone marrow aima poetic pluripotent cells.
However all innate cells (with the** exception of natural killer cells**) come from the myeloid cell
As such macrophages and neutrophils come from myeloid cells
and natural killer cells come from Cellule progénitrice lymphoïde

Question 18

True or false:
Natural killer cells and T lymphocytes come from the same stem cell

Answer 18

True
Natural killer cell is the exception that comes from the lymphoid stem cells although it is innate immune system

Question 19

Describe the main roles of a macrophage

Answer 19

Main roles is to recognize a pathogen infected cells or dead cells and eat them
reconnaissance, ingestion et destruction

Question 20

What are pathogen specific patterns?

Answer 20

Pathogen specific patterns are patterns that can be recognized from innate immune cells. The essentially allow innate immune cells to make a difference between self and non self
So the macrophage might not recognize specifically which pathogen it’s trying to kill but it at least knows that it is a pathogen and not a self cell

Question 21

What is a Phagolysosome?

Answer 21

It is a small prison for pathogens inside macrophages where there will be digested and lysed

Question 22

True or false
The macrophage is not involved in signaling

Answer 22

False after the macrophage has ingested a pathogen it will release cytokines to alert the immune system and recruit more immune cells just like the complement system

Question 23

What are Chimiokine?

Answer 23

Cytokines are like messengers that cells use to talk to each other. They help the immune system know what’s going on and what needs to be done. They can tell immune cells to grow, divide, or even stop doing something.

Chemokines are a special type of messenger. They’re like a GPS for immune cells, guiding them to where they need to go. They help immune cells find their way to places where they’re needed, like sites of infection or inflammation.

So, while cytokines give orders to the immune cells, chemokines help them navigate and find their destination.

Question 24

Give three example of cytokine families

Answer 24

Interleukines (IL-)
Interferon (IFN-)
Tumor necrosis factor (TNF-)

Question 25

What is the role of neutrophils

Answer 25

For starters they are the most white blood cell in our blood
In simple terms they are pawns or soldiers that are trying to kill the bacteria
Because of their huge number when they arrive at the site of the infection following the chemokines

They are similar to macrophages but more brutal
They essentially drop bombs or granules in the infected environment to kill a lot of the bacteria and also kill a bunch of healthy cells in the progress
They die very quickly after finishing their job and they contribute to the formation of pus

Reconnaissance, ingestion et destruction du
pathogène (comme les macrophages)
Relargage de substances
Meurent rapidement et contribuent à la
formation de pus

Question 26

What are the four clinical signs of local inflammation

Answer 26

• Chaleur
• Rougeur (érythème)
• Œdème (enflure)
• Douleur

Question 27

What are the four clinical signs of a systematic inflammation

Answer 27

• Fièvre
• Baisse d’appétit
• Douleurs musculaires (myalgies)
• Augmentation du nombre de neutrophiles
  dans le sang (neutrophilie); le plus souvent.

Question 28

Provide an example of a inflammatory reaction without infection

Answer 28

A damaged human cell will release cells that are not supposed to be in the environemnt. Detected by macrophages which can also lead to an inflamatory response. The same inflamation signs found even when we hurt ourselves not only due to pathogens like when we tear a muscle or ligament (page 39)

This will help with healing. Usually not a lot of neutrophils recruited, more so macrophages to clean up

Question 29

How does a viral infection differ from a bacterial infection in terms of infection?

Answer 29

A virus infects by inserting inside of cells

Different from bacteria as viruses will enter inside the cells.

Question 30

How does the immune system attack an intracellular pathogen like a virus?

Answer 30

We have intracellular molecules that have receptors that can detect pathogen specific targets. And thus they can detect a pathogen.

When the pathogen is detected, the cell will release cytokines example cytokine IL-1

Question 31

Give an example in terms of viral infection and response of how a deficit can lead to an increased risk of infection

Answer 31

The under expression of the intracellular receptor that detects the virus and leads to the signalization via interferon IL-1

This can allow the virus to multiply more before it gets detected

Question 32

How does IL-1 signaling protect neighboring cells from the virus?

Answer 32

One of the things done by IL-1 is to paracrine and tell neighbour cells that there is a pathogen around.

And so the neighbour cells can reduce the receptors on its surface to prevent the binding of the virus. It could also stop its reproduction.

Question 33

True or False;

Les cellules NK font seulement partie de la réponse du système immunitaire innée aux bacterie et non pas aux infections virales

Answer 33

False

Viral and Bacterial

Question 34

D’où viennent les cellules NK (natural killer)?

Answer 34

These are the only innate cells that come from the lymphoid cells

Question 35

What is the main role of the natural killer cell For a viral response

Answer 35

NK cells check and patrol all cells to check if they are in a “healthy” state.

How?

They detect CMH-1 on the surface. All human cells will express a CMH-1 on their surface.

If NK sees a normal CMH-1, cell is healhty!

L’expression normale du complexe majeur d’histocompatibilité (CMH) de classe I à la surface des cellules
saines de l’hôte les protègent de la destruction par les cellules NK .

Question 36

What would happen to the CMH-1 receptor on a infected cell

Answer 36

One of the ways a cell respons to a virus is to alter the CMH-1 expression or completely remove it.

If this is detected by a NK (natural killer cell) this means DANGERR

Must kill -> Release granules and lead to death of the infected cell