neutrophils

Question 1

what percent are neutrophils in the blood

Answer 1

40-75

Question 2

how many neutrophils are produced each minute

Answer 2

60 million

Question 3

what is neutrophils half life

Answer 3

7hrs

Question 4

where are neutrophils produced and stored

Answer 4

bone marrow

Question 5

what are neutrophils crucial for

Answer 5

host defence against bacterial and fungal infection

Question 6

what factors increase no of neutrophils

Answer 6

stress, injury, infection and cytokines

Question 7

what do emergency cytokines do

Answer 7

switch off ebp alpha and increase granulocyte numbers

Question 8

how do neutrophils kill bacteria

Answer 8

engulfment

Question 9

what are rolling neutrophils tethered to

Answer 9

the blood vessels

Question 10

3 stages of neutrophil movement

Answer 10

rolling, adhesions and crawling, transmigration

Question 11

how is the movement of neutrophils controlled

Answer 11

neutrophils indergo a transient attachment to selectins
selectins interact with sugars on the surface of neutrophils with weak attachment to slow them down
once slowed down integrins bind to give fill arrest and firm adhesion
movement into tissues is driven by chemokines produced by inflammation

Question 12

molecular players in rolling, firm adhesion, diapedis and chemotaxis

Answer 12

rolling - selectins and selectin counter receptors
firm adhesion - activated integrins and Ig like couterparts
diapedis - integrins and enothelial cell adhesion molecules
chemotaxis - integrins and chemokines/chemokine receptors

Question 13

what is paracellular migration

Answer 13

movement between cells of the blood vessel wall

Question 14

what is transcellular migration

Answer 14

movement through endothelial cells by engulfment

Question 15

what are the 3 known selectins

Answer 15

e + p selectin and l selectins

Question 16

what are beta 2 integrins

Answer 16

adhesion molecules, alpha beta heterodimers
diff alpha chain, common beta chain
exclusive to immune system
CD11a and CD11b are most important as they are major adhesion receptors
undergo conformational changes from low, med to high affinity via inside out signalling
usually found in low affinity states and are activated by chemokines

Question 17

chemotaxis by neutrophils

Answer 17

allows neutrophils to chase infection
responds to sterile tissue injury in the liver
mediated by chemotatic factors / chemokines which bind to g protein coupled receptors on the neutrophils
results in polarisation and directed movement

Question 18

chemotatic factors

Answer 18

platelet activating factors,
FMLP-N-formylated peptides from bacteria and mitochondria
C5a and C5 break down product, anaphlotoxin

Question 19

how are g proteins activated

Answer 19

GTP replaces GDP

Question 20

what are primary opsonins and what are they needed for

Answer 20

IgG, complement factor C3 fragment, C3b and C3bi
most microorganisms wont be phagocytosed without opsonins
pseudopods extend to cover the particle that is opsonised
opsonins are generated to mediate phagocytosis

Question 21

IgG Fc receptors

Answer 21

the fab region reacts with the organism

the fc region interacts with the FcyR

Question 22

what is necessary for complete digestion of bacteria

Answer 22

lysosomes

Question 23

how does the phagosome help killing of bacterial through neutrophils

Answer 23

bacterium is phagocytosed by neutrophils
the phagosome fuses with azurophilic and specific granules
ph of the phagosome rises rises to activate the microbial response and the bacterium is killed
ph then decreases and fusion with lysosomes allows acid hydrolases to degrade the bacterium completely
the neutrophil dies by apoptosis and is phagocytosed by macrophages

Question 24

respiratory burst and generation of reactive oxygen species:
when is the NADPH complex assembled?

where is the complex assembled?

why is super oxide acted upon?

where are reactive O2 species generated?

why does the conversion to reactive O2 need to be highly regulated?

what do further reactions lead to?

Answer 24

following the activation of neutrophils with diverse products, especially microbial derivatives

in the neutrophil that is to be oxidised

super oxide is to be acted upon to be converted to hydrogen peroxide which can be converted to other O2 species by iron

at the cell surface

if it wasnt highly regulated it would lead to a lot of tissue damage

formation of other antimicrobial reactive oxygen species such as hydroxyl radicals and hypochloras

Question 25

what do membrane of granules contain

Answer 25

members of the NADPH complex

Question 26

what do muts in the NADPH complex lead to

Answer 26

mutations in the complex lead to diseases as infection cannot be efficiently degraded

Question 27

what is chronic granulomatous disease

Answer 27

a mut in the NOX2 of NADPH complex
recurring/persistant infection of soft tissue, lungs an other organs despite antibiotic treatment
symptoms = facial acne, inflam of nares, severe gingivitis, early pneumonia, excessive formation of granulomes in all tissue
treat with daily does of trimethoprim-sulfamethoxazole and INF-y to reduce frequency of infection

Question 28

what are NETs (neutrophil extracellular traps)

Answer 28

an antimicrobial pathway of neutrophils
they decondense nuclear dna/chromatin and release them into the cytoplasm to mix with granule derived antimicrobial peptides before extending weblike structures into the extracellular environment
they trap and kill a variety of microbes

Question 29

what do NETs require

Answer 29

reactive O2 species, granule proteins myeloperoxidase and neutrophil elastase

Question 30

how do nets work

Answer 30

neutrophils activate and the NE is released from azurophilic granules into the cytosol and translocates to nucleus where it cleave the histone to decondense chromatin
myeloperoxidase consumes H2O2 to generate HOCl and other oxidants - required for translocation of NE to the nucleus during NETosis

Question 31

what is NET deficiency associated with

Answer 31

susceptibility to fungal infection in patients with chronic granulomatous disease who do not generate reactive O2 species