Immune system

Question 1

What is the immune system?

Answer 1

It recognises and responds to non-self entities in the body

Question 2

Name some non-self entities that the immune system targets

Answer 2

Viruses, Bacteria, Parasites, malignancies and grafts

Question 3

Name some functions that the immune system has to undertake?

Answer 3

• detect and identify non-self
• Communicate with other cells
• recruit
• destroy or suppress

Question 4

What are the 2 types of immune tissues?

Answer 4

• Primary lymphoid tissues
• secondary lymphoid tissues

Question 5

When is something considered a primary lymphoid tissue?

Answer 5

When it produces white blood cells

Question 6

Name 2 structures in the primary lymphoid tissue?

Answer 6

• Thymus
• bone marrow

Question 7

Name two structures in the secondary lymphoid tissues?

Answer 7

• Spleen
• lymph nodes

Question 8

What else occurs in tissues?

Answer 8

Aggregations of immune cells also occur in other tissues (i.e. the gut)

Question 9

Compare Innate and adaptive immunity

Answer 9

Question 10

Activation of the innate immunity can increase what?

Answer 10

The memory responses of the adaptive system, increasing its effectiveness

Question 11

Tell me the relative activity of cells in the body when a infection arises

Answer 11

Question 12

Name some ways that pathogens can invade the body?

Answer 12

• Cuts/wounds/post-operation e.g. Staph. aureus
• Insect bites- (e.g. sand-fly-leishmania, mosquito –malaria)
• Animal bites ––environmental pathogens and rabies
• Airborne e.g. Mycobacterium tuberculosis
• Food E. coli & Salmonella
• Human behaviour IV drug user’s HIV and hepatitis

Question 13

In early experiments, 1845-1916, what did the scientist Metchnikoff show?

What did he incorrectly suggest?

Answer 13

• He showed that cells (white blood cells) termed phagocytes could ingest microbes- these were more active from vaccinated animals
• Metchnikoff (incorrectly) suggested that cells rather than serum components were the major effectors of immunity.
• Phagocytes were later identified as monocytes/macrophages and neutrophils as the major effector cells

Question 14

Name some defence mechanisms of the innate response to a virus

Answer 14

• mucus
• antigen presenting cells
• phagocytes
• cytokines
• neutrophils
• lymphocytes

Question 15

Name some non-specific defences and how they work/ what they produce?

Answer 15

Question 16

Whats inflammation, name some things that can cause it

Answer 16

Inflammation is a complex biological response of the body tissues to harmful sitmuli such as…

• pathogens
• damaged cells/ tissues
• irritants

Question 17

Tell me the steps to how inflammation allows the immune system access to damaged/ infected tissues in order to remove necrotic cells and tissues to intiate repair?

Answer 17

1. bacteria trigger macrophage to release cytokines and chemokines
2. vasodilation and increased vascular permeability cause redness, heat and swelling
3. inflammatory cells migrate into tissues releasing inflammatory mediators that cause pain

Question 18

Whats vasodilation?

What physical effects does it cause?

Answer 18

There is an increase in diameter of adjoining capillaries constriction of vessles transporting blood away

physical effects:

• redness
• swelling
• heat

Question 19

When theres inflammation, what do resident macrophages and damaged tissue cells release?

Answer 19

chemical signals and alter endothelia cells

Question 20

Name 3 processes that occur when inflammation is present?

Answer 20

1. Margination
2. Extravasation
3. Chemotaxis

Question 21

Whats margination?

Answer 21

Inflammation attracts monocytes and neutrophils- rolling (adherence) to endothelial of venules

Question 22

Whats Extravasation?

Answer 22

Emigration from vessel between the endothelial cells into the tissue

Question 23

Whats Chemotaxis ?

Answer 23

Migrate to the site of injury/ invasion

Question 24

During the margination of neutrophils, what generally occurs?

Answer 24

The RBC clump together to make space for neutrophils in the vessel

Question 25

Whats meant by **neutrophil nets ?**

Answer 25

When neutrophils shoot out DNA/chromatin and coat bacteria

Question 26

Name the cells of the immune system Their classification Their primary function(s)

Answer 26

Question 27

Where are monocytes found? What happens when they are activated in tissues?

Answer 27

Monocytes are found in the blood, when they are activated in tissues they differentiate into macrophages

Question 28

Where may macrophages reside?

Answer 28

They may reside for a long time in the same tissue

Question 29

Whats the role of macrophages?

Answer 29

To remove pathogens and dead or dying cells by **phagocytosis** (neutrophils and eosinophils are also phagocytes)

Question 30

Explain the process of phagocytosis

Answer 30

Question 31

When is pathogen killing initiated? Whats released?

Answer 31

Once the phagocytic vacuole fuses with a lysosome forming a phagolysosome with release of: * oxygen radicals * chlorine products * Nitric oxide pathway

Question 32

What is NADPH oxidase? Where is it located during phagocytosis?

Answer 32

NADPH oxidase is a membrane-bound enzyme complex It faces the inner space of phagosomes

Question 33

During phagocytosing, what does the cell undergo?

Answer 33

A massive increase in metabolism

Question 34

What does the respiratory burst produce?

Answer 34

Reactive oxygen species (ROS)

Question 35

What reaction does NADPH oxidase catalyse?

Answer 35

Question 36

When Superoxide, O₂^- is produced, what reactions can occurs, (with enzymes), to produce toxic products? What can these products destroy?

Answer 36

Superoxide, Hydrogen Peroxide, Chlorine, Hypochlorite and Hydroxyl radical, all extremely toxic **destroying lipid membrane and bacterial DNA** (kept in vesicles to help protect the cell)

Question 37

What kind of receptors can the innate immune system use and what are these?

Answer 37

The innate immune system uses receptors that can detect the repeating patterns in the surface of microorganisms

Question 38

Name some pattern recognition receptors Where do they bind/ recognise?

Answer 38

* **mannose receptor** binds mannose residues on pathogen surface * **glycan receptor** binds to polysaccharides of bacteria and yeast * **scavenger receptor** recognises complex sugars on yeast and bacteria * **TLR (Toll-like receptor)** binds to LPS (lipopolysaccharide) on the cell wall of gram-negative bacteria * **Complement receptor (CR)** recognises complement covered structures on yeast and bacteria

Question 39

What are **toll like receptors?**

Answer 39

Transmembrane receptors that signal to immune cells the type of pathogen that has invaded

Question 40

Name the Toll like receptors What are each of their ligands? Whats their source? Provide an example for each?

Answer 40

Question 41

Here is an example of LPS and TLR4

Answer 41

Question 42

What are **interferons?**

Answer 42

cytokines that inhibit viral replication within cells

Question 43

What do activated macrophages release and what does this stimulate?

Answer 43

Activated macrophages release **IL-12** This stimulates **IFNγ** by natural killer cells

Question 44

What does IFNγ lead to?

Answer 44

further macrophage activation in a feedback loop amplifying innate immune responses- increasing phagocytosis and iNOS expression

Question 45

What do the interleukins **IL-1** and **TNFα** induce?

Answer 45

endothelial cells to express adhesion molecules allowing neutrophils and monocytes to bind and leave the bloodstream

Question 46

What is **IL-8?**

Answer 46

A potent neutrophil chemoattractant and activates macrophages

Question 47

What do TNFα, PAF and PG act directly on?

Answer 47

endothelium to increase permeability

Question 48

What does PAF cause?

Answer 48

platelets to release histamine also increases vascular endothelial permeability