Immunology

Question 1

What do all blood cells stem from?

Answer 1

Haematopoeitic pluripotent stem cells

Question 2

What is the role of neutrophils in immunity?

Answer 2

Phagocytosis (innate immunity)
Has two granules which are involved in killing:
Primary lysosomes (contain myeloperoxidase, acid hydrolyses, defensins)
Secondary granules (lactoferrin and lysozyme)

Question 3

What is the role of monocytes in immunity?

Answer 3

In tissues differentiate into macrophages.
Main role: remove anything foreign or dead
Can bind many types of microbe

Question 4

What is the role of basophils and mast cells in immunity?

Answer 4

Express IgE receptors- binding causes de-granulation, releasing histamine
Mainly involved in immunity to parasitic infections and allergic reactions
Same thing except mast wells are only in tissue

Question 5

What is the role of eosinophil in immunity?

Answer 5

Mainly associated with parasitic infections and allergic reactions.
Granules contain major basic protein which is a toxin for worms

Question 6

What is the role of T-lymphocytes in immunity?

Answer 6

Recognise peptide antigen displayed by antigen presenting cells

Question 7

What are the 4 types of T-cell?

Answer 7

1) T helper 1 (Th1)- helps immune response, kills intracellular pathogens (CD4)
2) T helper 2 (Th2)- helps produce antibodies- extracellular pathogens (CD4)
3) Cytotoxic T cell- can kill cells directly (CD8)
4) T reg- regulates immune response

Question 8

What is the role of B-lymphocytes in immunity?

Answer 8

Recognise antigen displayed by antigen presenting cells
Express membrane bound antibody on cell surface
Differentiate into plasma cells that make antibodies

Question 9

What is the role of natural killer cells in immunity?

Answer 9

Type of lymphocyte, recognise and kill virus infected cells and tumour cells by apoptosis.
Found in spleen/tissues

Question 10

What is the role of complement in immunity?

Answer 10

They trigger phagocytic cells and antibodies to do the following: phagocytosis, inflammmation (by attracting marcophages and neutrophils), and membraneattack
Must be activated to be functional.

Question 11

What are the three ways that compliment is activated?

Answer 11

1. Classical Pathway: binds to antibody-antigen complex
2. Alternative pathway: compliment binds to the microbe
3. Lectin pathway: activated by mannose binding lectin (on microbe) binding to mannose

Question 12

What is the role of cytokines in the immune system?

Answer 12

‘Hormones of the immune system’

Proteins secreted by immune and non-immune cells

Question 13

What are the different types of cytokines and their functions?

Answer 13

INTERFERONS- antiviral resistance in uninfected cells, limit spread of infection.

INTERLEUKIN- cause cells to divide, differentiate, and secrete factors.

COLONY STIMULATING FACTORS- involved in directing the division and differentiation on bone marrow stem cells, precursors of leukocytes

TUMOUR NECROSIS FACTORS- mediate inflammation and cytotoxic reactions

Question 14

What is the role of chemokines in immunity?

Answer 14

‘Cytokines that are chemotactic’

Direct movement of leukocytes from the blood stream into tissues or lymph organs by binding to specific receptors on cells

Question 15

Function of IgG

Answer 15

Protects body from infection (70% of immunoglobulins)

Question 16

Function of IgM

Answer 16

Main primary response to infection, initial contact with antigen

Question 17

Function of IgA

Answer 17

Immune protection in mucous membranes

Question 18

Function of IgD

Answer 18

Functions mainly as cell surface receptors for antigen (not secreted)

Question 19

Function of IgE

Answer 19

Associated with allergic response and parasitic defence. Basophils and mast cells have high affinity for it

Question 20

What is innate immunity composed of?

Answer 20

Physical and chemical barriers
Phagocytic cells
Blood proteins (complement and acute proteins- soluble factors)

Question 21

What is the process of extravasation?

Answer 21

Allows neutrophils to enter tissues at site of infection

Microbe is detected in tissue
Chemokines released and endothelial cells of blood vessel become sticky
Neutrophils bind to the sticky endothelium and interactions with chemokines
Moves up chemokine gradient in tissue to site of infection

Question 22

How do macrophages and neutrophils kill microbes after engulfing them?

Answer 22

1. Oxygen dependent- ROS

2. Oxygen independent- enzymes

Question 23

What cells are antigen presenting cells? (APC)

Answer 23

Dendritic cells
Macrophages
B cells

Question 24

What is Major Histocompatibility Complex (MHC) and what is its function?

Answer 24

A set of cell surface proteins essential for the acquired immune system to recognize foreign molecules

The main function of MHC molecules is to bind to antigens derived from pathogens and display them on the cell surface for recognition by the appropriate T-cells

T Cell receptors can only recognise foreign antigens when combined with MHC

Question 25

Can T-cells respond to soluble antigens?

Answer 25

Nah, only intracellular presented antigens

Question 26

What do Pattern Recognition Receptors do?

Answer 26

They detect pathogens by recognising ‘pathogen associated molecular patterns (PAMP)’ on them

When activated they release cytokines which shape the T-cell response

Question 27

What are the different types of Pattern Recognition Receptors?

Answer 27

SECRETED AND CIRCULATING PRRs:

• lectins and collectins (activate complement, improve phagocytosis)
• pentraxins (activate complement, promote -phagocytosis)
• mannose binding lectin
• surfactant proteins A and D

CELL ASSOCIATED PRRs:

• Toll like receptors (important-recognise extracellular patterns)
• C-type lectin receptors (CLR)
• Nucleotide oligomerisation receptors (NLR) (intracellular)
• RIG-1 like receptors (intracellular)

Question 28

Give some examples of Pathogen Associated Molecular Patterns (PAMP)

Answer 28

• double stranded RNA (some viruses)
• CpG motifs (bacteria)
• Gram negative has thin peptidoglycan in wall, Gram positive has thick

Question 29

Give some examples of Toll-Like Receptors (TLR)

Answer 29

• TLR4: recognises bacterial endotoxins
• TLR3, TLR7-8: Can see ssRNA in viruses
• TLR9: Can tell between commensal and harmful bacteria
• TLR2: can see gram positive bacteria

Question 30

Definition: Allergy

Answer 30

An abnormal response to harmless foreign material

Question 31

Definition: Atopy

Answer 31

A hereditary disposition to develop allergies against common environmental allergies

Question 32

What does high affinity IgE do?

Answer 32

IgE binds to cell and coats it- all the IgE and their receptors cluster together on cell
Signalling cascade occurs in cell which triggers cellular response

Eosinophils, mast cells, basophils all express a high affinity IgE receptor

Question 33

What does low affinity IgE do?

Answer 33

Regulates IgE synthesis
Triggers cytokine release by monocyts
Antigen presentation by cells

Question 34

What do mast cells do?

Answer 34

• Produce histamine: dilation and cholinergic reflex
• Produce chemotatic factors (cytokines) to draw in other cells
• Produce proteases and proteoglycans: package granules to replace water and clot blood

Question 35

What activates a mast cell?

Answer 35

• Anything that binds IgE (allergens, bacterial/viral antigens)
• Phagocytosis of enterobacteria
• Direct activators (cold/mechanical deformation, drugs)

Question 36

What are the features of an allergen?

Answer 36

• Directly activate mast cells
• Low doses (high doses desensitize)
• Nasal/skin delivery
• Particulate delivery of antigens
• Presence of weak PAMPs

Question 37

What is the concept of cancer immunosurveillance?

Answer 37

The immune system can recognise and destroy potential transformed cells

Question 38

What is the concept of cancer immunoediting?

Answer 38

Tumours are unstable, therefore immune systems can kill and change the tumour resulting in tumour escape and recurrence

Question 39

What are examples of active immunity?

Answer 39

• Vaccination

- Augmentation of host immunity to tumours with cytokines and costimulators