Innate Immunity

Question 1

What are the three internal innate defences?

Answer 1

Fever
Chemical signals
Inflammation

Question 2

What are neutrophils?

Answer 2

Most abundant WBC that self destruct after devouring pathogens

Question 3

What is pus?

Answer 3

Neutrophils

Question 4

When are neutrophils triggered?

Answer 4

When cells release chemicals that begin leukocytosis

Question 5

True or false: neutrophils are usually used to fight viral infections

Answer 5

FALSE-they are used to fight bacterial infections

Question 6

What are the two types of macrophages?

Answer 6

Free

Fixed (eg in liver)

Question 7

What is the main difference between macrophages and neutrophils?

Answer 7

Macrophages can repeatedly engulf pathogens whereas neutrophils self-destruct after devouring one pathogen

Question 8

Where are macrophages produced?

Answer 8

Bone marrow

Question 9

What do natural killer (NK) cells do?

Answer 9

Kill own body cells if they become infected with a virus or become cancerous

Question 10

How do NK cells carry out their function?

Answer 10

Normal healthy cell contains a special protein on its surface called MHC1
If the cell becomes infected, it stops making this protein
If NK cell detects a defective cell, it doesn’t swallow it like a macrophage would but instead, it pokes it with an enzyme that triggered apoptosis

Question 11

What does MHC1 stand for?

Answer 11

Major histocompatibility complex

Question 12

What are the characteristic signs of inflammation?

Answer 12

Rubor = redness
Tumour = swelling
Calor = heat
Dolor = pain
Loss of function

Question 13

What do histamine and other inflammatory chemicals do?

Answer 13

Increase permeability of blood vessels, causing nearby capillaries to release protein-rich fluids. This causes swelling and the leaked protein helps to clot blood and form scabs

Question 14

What is the name of the chemical released when the body detects too many pathogens?

Answer 14

Pyrogen

Question 15

What do pyrogen chemicals do?

Answer 15

They stimulate the hypothalamus to increase the body temperature (systemic fever)

Question 16

How does a systemic fever help fight an infection?

Answer 16

Increases cell metabolism so the body can heal faster and it tells the liver and spleen to hold onto all its iron and zinc so that it can’t contribute to bacterial growth

Question 17

What is the oxygen-independent method of killing a pathogen?

Answer 17

Using hydrolytic enzymes inside lysosomes

Low pH prevents the growth of other pathogens

Question 18

What is the oxygen-dependent method of killing a pathogen?

Answer 18

Activated phagocytes produce a number of reactive oxygen species

Question 19

What are the stages of phagocytosis? (8)

Answer 19

1. Phagocytes migrate towards site of infection
2. Recognise targets
3. Ingestion
4. Formation of phagosome
5. Formation of phagolysosome
6. Digestion
7. Forming residual body
8. Discharge of waste

Question 20

Define opsonisation

Answer 20

Binding of an opsonin such as antibodies and complement to a receptor on the pathogen’s cell membrane, marking it for ingestion and destruction by a phagocyte

Question 21

What is a residual body?

Answer 21

Vesicles containing indigestible materials which are then either secreted by the cell via exocytosis or remain as fine granules within the cytosol

Question 22

What are the two lines of defence of the innate immune system?

Answer 22

1. Mechanical and chemical barriers

2. Cellular eg. Phagocytes or protein dependent eg. Complement

Question 23

What does complement consist of ?

Answer 23

Group of serum proteins

Question 24

What does complement activate?

Answer 24

Inflammation
Cell destruction
Opsonisation

Question 25

How do the complement proteins respond and what is this called?

Answer 25

They respond in a sequential manner called the complement cascade

Question 26

What are the two ways in which the complement cascade can be activated?

Answer 26

Classical pathway

Alternative pathway

Question 27

What is activated in the classical pathway and when?

Answer 27

C1 is activated when it binds to an antigen-antibody complex

Question 28

What is activated in the alternative pathway and when?

Answer 28

C3b is activated when it reacts with antigens such as the bacterial cell wall.

Question 29

Define oedema

Answer 29

Accumulation of excessive amount of watery fluid in cells, tissues or serous cavities

Question 30

What is lymphedema?

Answer 30

Swelling (especially in subcutaneous tissues) as a result of obstruction of lymphatic vessels or lymph nodes and the accumulation of large amounts f lymph in the affected region

Question 31

Why does lymphedema not pit?

Answer 31

Lymph has a high protein content and the activation of collagen and fibroblasts makes the skin very scaly and thick so it will not pit

Question 32

How does oedema form?

Answer 32

Increased hydrostatic pressure within blood vessels
Reduced oncotic pressure within blood vessels
Increased blood vessel permeability (inflammation)

Question 33

In congestive heart failure, the right and left ventricles are not pumping properly so they dilate. Venous blood ‘dams up’ because the right ventricle cannot cope with the venous return. What will happen to the pressure in the veins?

Answer 33

Increases as the right side is not pumping effectively so there is a build up of hydrostatic pressure in the veins

Question 34

What is a starling force?

Answer 34

A force that governs whether fluid moves into or out of the capillaries

Question 35

What is the arteriolar capillary hydrostatic pressure?

Answer 35

35mmHg

Question 36

What is the venular capillary hydrostatic pressure?

Answer 36

15mmHg

Question 37

What is the blood colloid oncotic pressure?

Answer 37

25mmHg

Question 38

Why does oedema often appear first at the ankles?

Answer 38

Gravity causes a vertical gradient of venous pressures

Question 39

Where would you expect oedema to appear in someone who is lying/sitting in bed?

Answer 39

Sacral oedema (lower back)