The immune response

Question 1

A pathogen has to (4)

Answer 1

1. Colonise host tissues
2. Avoid host defence
   mechanisms
3. Grow within host tissues
4. Cause damage to the
   host

Question 2

Colonisation is

Answer 2

microorganisms that are carried normally by the host, cause no harm and produce no overt symptoms (commensal)

Question 3

Infection is

Answer 3

the invasion of a host organism’s bodily tissues by disease causing organisms. This can result in
disease

Question 4

Innate immunity is

Answer 4

NON SPECIFIC, IMMEDIATE response, NO IMMUNOLOGICAL MEMORY

humoral: enzymes, cytokines
(cellular: phagocytes, NKCs, pattern receptors)(inflammation, complement system)

Question 5

Adaptive immunity is

Answer 5

SPECIFIC to ANTIGEN, exposure-response LAG, IMMUNOLOGICAL MEMORY
(humoral: antibodies, cytokines)
(cellular: B cells, T cells)
(antigen processing and presentation)

Question 6

Most immune cells are circulatory except

Answer 6

1. Alveolar macrophages (fixed macrophages and dendritic cells have protrusions to bring pathogens in)
2. M cells (microfold cells in the gut, don’t have as many villi as surrounding gut cells - key mediators in pulling in pathogens through the epithelial layer (through phagocytosis, endocytosis, transcytosis) and feed to macrophages in the tissues or bloodstream)

Question 7

The professional phagocytes are:

Answer 7

monocytes 
macrophages 
neutrophils 
tissue dendritic cells 
mast cells

Question 8

A professional phagocyte takes up

Answer 8

endocytosis and destroyed within a phagolysosome

Question 9

Steps of killing in the phagolysosome

Answer 9

1. bacteria are engulfed
2. taken up into a phagosome
3. ph lowers in the phagosome
4. in professional phagocytes, phagosome fuses with the lysosome
5. release of cell products and presentation on phagocyte surface

Question 10

What is opsonisation?

Answer 10

the process by which the pathogen is marked for ingestion and eliminated by the phagocytes

Question 11

Phagocytes are the interplay between

Answer 11

the innate and adaptive immune system

Question 12

c3b complement

Answer 12

C3b is the larger of two elements formed by the cleavage of complement component 3, and is considered an important part of the innate immune system. C3b is potent in opsonization: tagging pathogens, immune complexes, and apoptotic cells for phagocytosis

• antibodies recognise structures on the surface of a bacteria
• macrophages have an FC receptor
• part of an antibody is called the FC chain
• if a macrophage has an FC receptor it will pick up a bacteria and coat it with antibody
• coating of a bacteria is called opsonisation
• c3b is a protein involved in the complement cascade (extra reading?) C3b has a thioester bond which makes it really reactive so it will react with amine and hydoxyl groups on the surface of the bacteria and bind to the bacteria covalently
• macrophages have a c3b receptor, stronger interaction and macrophages more likely to take up the pathogen
• if the pathogen has been subjected to antibodies (FC) and C3B uptake is a lot stronger

Question 13

Professional phagocytes produce

Answer 13

ROS

in the lumen of the phagolysosome, but they can also be secreted by macrophages

ROS’s stem from the production of superoxide anion
(O2•− ) by NADPH oxidase.
The O2•− is rapidly
transformed to numerous other reactive oxygen species
(ROS),mainly H2O2, OH•, and HOCl.
Known as the ‘respiratory burst’.

Question 14

Macrophages acidify the phagosomal lumen by

Answer 14

recruiting V-ATPase (H+ pump)

Question 15

NRAMP

Answer 15

antimicrobial peptide produced by phagocytes

natural resistance associated macrophage protein (strips divalent magnesium from bacteria so they can’t grow)

Question 16

antimicrobial peptides are delivered to the phagosome by

Answer 16

granular organelles in neutrophils and by fusion with the lysosome in macrophages

Question 17

Lactoferrin is an antimicrobial peptide produced by the host that

Answer 17

strips iron: makes iron unavailable to bacteria

Question 18

defensins and cathelocidins are antimicrobial peptides that bind to

Answer 18

the membrane causing cellular destruction

Question 19

the Lysosome breaks down

Answer 19

sugar chains in peptidoglycan

Question 20

cytokines are produced by phagocytes to

Answer 20

activate other phagocytes and recruit monocytes

PAMPS (pathogen associated molecular patterns) are recognised by TLRs

DAMPS recognise host cell damage

Question 21

PAMPS

Answer 21

Lipopolysaccharides, DNA, cell surface proteins etc are all PAMPs which are recognised by TLRs

Question 22

NODS recognise

Answer 22

peptidoglycan

Question 23

TLRs

Answer 23

a class of proteins, are single, membrane-spanning, non-catalytic receptors usually expressed on macrophages and dendritic cells, that recognize structurally conserved molecules derived from microbes

Question 24

chemokines

Answer 24

chemotactic and chemokinetic for leukocytes: stimulate cell migration and attract phagocytic cells and lymphocytes. Central role in inflammatory response.

Question 25

hematopoetins

Answer 25

stimulate and regulate growth and differentiation processes involved in blood cell formation (hematopoeisis)

Question 26

interleukins

Answer 26

produced by lymphocytes and monocytes, regulates the growth and differentiation of other cells, particularly lymphocytes and hematopoeic stem cells

Question 27

TNFs

Answer 27

cytotoxic to tumour cells, promote inflammation, fever and shock (and some apoptosis)

Question 28

Following destruction of an ingested microbe, what happens?

Answer 28

Phagocytes as APC’s – recognition by CD8+ and CD4+ T cells
CD4 = Th
CD8 = Tk

Question 29

CD4+ T cells recognise

Answer 29

antigen presented by MHC II molecules on phagocytes

Question 30

CD8+ T cells recognise

Answer 30

antigen presented by MHC I molecules
beta2 microglobulin is a key part of the presentation of antigen to CD8 t cells. The proteosome chops up foreign cell products from the CYTOSOL, send them to the ER to be sent to MHCI (NOT FROM THE PHAGOSOME)