Innate Immunity

Question 1

What is innate immunity?

Answer 1

Rapid cellular/soluble component immune response present from birth, using PAMPs/DAMPs to detect microbial structures and damage as well as missing self

Question 2

Name the 4 types of defensive barrier

Answer 2

Anatomical
Physiological
Phagocytic
Inflammatory

Question 3

What are the anatomical barriers?

Answer 3

Skin (mechanical)

Mucous membranes

Question 4

What are the physiological barriers?

Answer 4

Fever
Low Stomach pH
Chemical mediators: Lysozymes, interferons, complement

Question 5

What are phagocytes?

Answer 5

Cells that ingest material

Question 6

What is the inflammatory barrier?

Answer 6

Local increased vascular permeability to allow cell escape to enhance immune function

Question 7

Name the major phagocytic cell types:

All 7 of ‘em!

Answer 7

Neutrophils
Eosinophils
Basophils
Monocytes/Macrophages
Mast Cells
Dendritic cells
Natural Killer Cells

Question 8

What are neutrophils?

Answer 8

Phagocytes with multi-lobed nuclei.

Short lived; circulate in blood then migrate to tissues

Question 9

Which cells are first recruited to the site of damage?

Answer 9

Neutrophils

Question 10

Which cells defend against parasitic infection?

Answer 10

Eosinophils

Question 11

What are eosinophils?

Answer 11

Phagocytes.
Release granules to defend against parasites
Help B-cells produce IgA

Question 12

What are basophils?

Answer 12

Granule releasing cells

They act as antigen-presenting cells for antibody mediated immunity

Question 13

What is the difference between Monocytes and Macrophages?

Answer 13

Monocytes in blood

Macrophages in tissue

Question 14

What are macrophages?

Answer 14

Important for phagocytosis
“Big Eaters”
Release cytokines
Present antigen fragments to T-cells

Question 15

What are mast cells?

Answer 15

Release histamine-containing granules

Pro-inflammatory

Question 16

What do dendritic cells do?

Answer 16

Capture antigens and present them to T-cells

Question 17

What do Natural Killer Cells do?

Answer 17

Lyse infected cells
(no antigen-specific receptors)
Secreet Interferon-y

Question 18

How do neutrophils enter tissues?

Answer 18

Diapedesis and Chemotaxis
Simmilar way to Lymphocytes
Selectin Binding (with rollin’)
Then Integrin activation and strong binding, immobilisation and Diapedesis

Question 19

What proportion of leukocytes are neutrophils?

Answer 19

50-70%

Question 20

What causes a neutrophil to enter a tissue?

Answer 20

Damage causes chemokines to be released which bind to endothelial layer.
Neutrophils recept these which actiates integrin…

Question 21

How do Neutrophils know where to go once they enter a tissue?

Answer 21

Chemotaxis:

They follow the gradient of chemokines which gets stronger towards the site of damage/infection

Question 22

Which molecules function as opsonins?

Answer 22

Antibodies and Complement

Question 23

What is Opsoninisation?

Answer 23

Coating of microorganism with opsonins (e.g. antibodies) to facilitate phagocytosis.

Question 24

What are the 2 mechanisms Neutrophils use to kill?

Answer 24

Oxygen independent: Enzymes (hydrolytic, lysozymes etc.) and antimicrobial peptides
Oxygen dependent: Free radicals, H2O2, anything that sounds toxic (e.g. you)

Question 25

What do neutrophils need to do to fight infection? | List the 4 steps:

Answer 25

Move from circ into tissues Bind to pathogen Phagocytose pathogen Kill it

Question 26

How do neutrophils trap microbes?

Answer 26

Extracellular traps: they release granule net-like materials which form extracellular fibres to trap microbes

Question 27

What do macrophages do once they've eaten a pathogen?

Answer 27

Release soluble cytokines to recruit further cells

Question 28

What is (NK) target cell recognition?

Answer 28

Under viral stress, cell upregulates stress-induced molecules that activate natural killer cells and downregulate inhibitory molecules so NK cells are not inhibited to kill cell

Question 29

What are NK cells useful for fighting?

Answer 29

Viral infections | Tumours

Question 30

How are NK cells regulated?

Answer 30

Have activatory and inhibitory receptors

Question 31

Name 5 types of cytokine

Answer 31

``` Interleukins Interferons Chemokines Growth factors Cytotoxic tumour necrosis factors ```

Question 32

What do interferons do?

Answer 32

Interfere with viral replication

Question 33

What do growth factors do?

Answer 33

Help stem cells differentiate and proliferate

Question 34

What do cytotoxic tumour necrosis factors do?

Answer 34

Induce programmed cell death in target cells

Question 35

How do cytokines work?

Answer 35

Producing cell makes them in granules. Exocytose | Bind to receptors on cells, effect gene regulation (up/downregulate)

Question 36

Name the 3 locational modes of cytokine activity

Answer 36

Autocrine: on self Paracrine: on nearby cells Endocrine: via circulation to distant cell

Question 37

How many types of interferons are there, and what produces them?

Answer 37

2. Only immune cells produce type 2 Many cells produce type 1

Question 38

What is complement?

Answer 38

Glycoprotein enzyme that 'complements' the action of a specific antibody

Question 39

Where are the components of the complement system produced?

Answer 39

Mainly liver | + Monocytes and macrophages

Question 40

What is the complement system?

Answer 40

Complex system of ~30 glycoproteins that from a triggered enzyme cascade

Question 41

What happens to the complement system when it is activated?

Answer 41

Inactive precursors are cleaved, and the cleaved sites become pro-inflammatory molecules.

Question 42

What are the names of the 3 activation pathways of complement?

Answer 42

Classical Alternative Lectin

Question 43

What do all 3 complement activation pathways result in?

Answer 43

Activation of C3b; final common pathway

Question 44

What is the classical pathway?

Answer 44

Antibody binds to antigen on pathogen. | Conformational change in antibody leads to complement activation

Question 45

What is the alternative pathway?

Answer 45

Direct activation of complement system by surfaces of pathogens themselves.

Question 46

What is the Lectin pathway?

Answer 46

Lectin: Carbohydrate binding protein; antibody-independent activation. Is a pattern recognition receptor, binds to patterns only present on pathogens

Question 47

What does activation of C3b lead to?

Answer 47

Formation of Membrane Attack Complex (MAC)

Question 48

What is the membrane attack complex?

Answer 48

What lyses infected cells or pathogens.

Question 49

What are the control mechanisms of complement?

Answer 49

Short half-life | Regulatory proteins on self cells, prevent complement mediated lysis of self (eg. CD59)

Question 50

What are the functions of complement?

Answer 50

Cell lysis Opsoninisation Pro-inflammatory effects Clear Immune complexes (antibody-antigen)

Question 51

What might a systematic 'acute-phase' response result in increased production of?

Answer 51

C-reactive protein (clinical measurement of inflam) Mannan-binding Lectin Complement Fibrinogen