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Comparative Immunology Midterm 2 > Neutrophils > Flashcards

Neutrophils Flashcards

1
Q

What is another name for Ns?

A

Polymorphonuclear (PMN) cells

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2
Q

True or false - Neutrophils are the last to reach the site of trauma

A

FALSE - they’re the first

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3
Q

What are N called in birds?

A

heterophils

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4
Q

N are potent effectors. What are their 3 effector functions?

A

phagocytosis, degranulation and formation of extracellular traps

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5
Q

What does it mean by N are temporally limited?

A

This means that they don’t last very long

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6
Q

What is the regulatory function of N?

A

recruitment of M0 to the tissues

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7
Q

True or false - N contribute to extensive host tissue damage

A

TRUE

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8
Q

How do N minimize host tissue damage?

A

rapid granulocyte recruitment, short lifespan, replacement by Mo derived M0s

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9
Q

What molecules are required for granulocyte differentiation?

A

IL3, IL6, GM-CSF, G-CSF, and specifically IL8 (CXCL8) for N

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10
Q

N do 3 things rapidly. What are these?

A

rapidly produced to maintain numbers in circulation, rapidly mobilized from circulation to damaged tissue, rapidly replaced during granulopoises

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11
Q

How were N initially subdivided?

A

By the presence of MPO. MPO+ = auzurophil granules. MPO- = specific granules

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12
Q

What are the 5 enzymes present in auzurophil granules?

A

elastase, cathespin G, proteinase 3, MPO, lysozyme

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13
Q

What is the function of elastase?

A

N endothelial cell adhesion

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14
Q

What are the functions of cathespin G?

A

bacteriocidal, tissue remodelling, DC and Mo trafficking

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15
Q

What is the function of proteinase 3?

A

activate cells in close proximity to secrete Mo cytokines

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16
Q

What is the function of MPO?

A

generation of Ras

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17
Q

What are the functions of lysozyme?

A

destroys peptidoglycans of Gran 1’ve bacteria, innate opsonin

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18
Q

What are the 2 cationic proteins present in auzurophil granules?

A

defensins and azurocidin

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19
Q

What is the function of defensins?

A

interaction with bacteria to kill them!

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20
Q

What are the functions of azurocidin?

A

antimicrobial, increase endothelial cell adhesion for Mo and DC & Mo trafficking

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21
Q

What do specific granules contain?

A

aghesion molecules, TNF receptors, collagenase, lactoferrin & haptoglobin (iron binding molecules)

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22
Q

What do gelatinase granules contain?

A

adhesion molecules, matrix metalloproteins, TNF receptors, lysozyme and arginase

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23
Q

What are teh functions of matrix metalloproteins?

A

remodel ECM to increase ease of cell migration into tissues and cleave cytokines to increase or decrease bioactivity

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24
Q

During entry into tissues, N release secretory vesicles containing what that are deposited in the cell membrane to bind ligands?

A

adhesion molecules, PRRs, cytokine receptors, chemokine receptors, Fc receptors

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25
Q

What is the order of release of granule types?

A

gelatinase, auzurophil then specific

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26
Q

Once in the tissue, N release another vesicle what creates?

A

a chemokine gradient for infiltration of M0

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27
Q

What are the 4 stages of N extravasion?

A

tethering, rolling & adhesion, increase adhesion and N activation, trans-endothelial cell migration

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28
Q

How does Stage 1 of N extravasion work?

A

P-selectin on endothelial cells in up regulated by detection of PAMPs which will attach to the N L-selectin so N now transiently attaches

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29
Q

What is the expression of L-selectin regulated by?

A

ADAM17

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30
Q

How does Stage 2 of N extravasion work?

A

endothelial cells secrete platelet-activating factor (PAF) which triggers rolling of the N. N adhesion is facilitated by up-regulation of ICAM 1&2 by the endothelial cell and release of elastase by N which cleaves leukosialin (anti-adhesion) from endothelial cells

31
Q

Expression of adhesion molecules ICAM 1&2 is regulated by?

A

ADAM17

32
Q

How does Stage 3 of N extravasion work?

A

N releases P-selectin and endothelial cells E-selectin to increase adhesion. N requires a dual signal to activate. Signal causes release of some granules therefore loosening tissue matrix allowing for migration

33
Q

What is the dual signal N requires for Stage 3 of N extravasion?

A

1 - ICAM/integrin interaction

2 - TNFalpha, CSCL8 or C5a

34
Q

How does Stage 4 of N extravasion work?

A

attachment of N to adhesion molecules in endothelial cell tight junctions and subsequent protease digestion of the basement membrane of endothelial cells

35
Q

What are the 4 stages of N phagocytosis?

A

Chemotaxis, adherence and opsinization, Ingestion, destruction

36
Q

How does stage 1 of N phagocytosis work?

A

receptors called lamellipodia on N detect chemotactic agents in tissues to direct N movement

37
Q

How does stage 2 of N phagocytosis work?

A

opsonins are posatively charged while cell membranes (host and microbe) are negatively charged so they bind and facilitate phagocytosis

38
Q

true or false - opsonins are not species and age specific

A

false

39
Q

Neonates rely heavily on _______ opsonins but receive _______ opsonins through passive immunity

A

innate, acquired

40
Q

Fish and chickens’ maternal acquired opsonins are deposited where?

A

in the yolk sac during egg development

41
Q

What are the 5 innate opsonins?

A

MBL, lysozyme, serum amyloid A, C-reactive protein, C3 breakdown products

42
Q

What are the 2 acquired opsonins?

A

Igs via Fc receptros, IgM + Cl via C1Q receptor

43
Q

What two molecules can perform opsonin-independent phagocytosis?

A

mannose receptors and some integrins

44
Q

How does stage 3 of N phagocytosis work?

A

N pseudopodia surround the particle forming a phagosome which combines with lysosome to form phagolysosome.

45
Q

What happens when the particle is too big to phagocytise?

A

The N will release some granular content to break down the particle but this will also damage host tissue

46
Q

How does stage 4 of N phagocytosis work?

A

Kills the particle via two mechanisms

47
Q

What are the two mechanisms N uses to kill the particle?

A

(1) Oxygen dependent and (2) oxygen independent

48
Q

Draw and describe the oxygen dependent pathway

A

do it

49
Q

How are N protected from exposure to ROS toxicity?

A

hydrogen peroxide splits H2O2 into O and H2O
glutathione (GSH) reduces oxidants
iron-binding proteins reduce iron bioavailability

50
Q

The oxygen independent pathway is critical for what kind of species?

A

those lacking MPO (ex. chicken)

51
Q

How does the oxygen independent pathway work?

A

microbial oxidation occurs which decreases pH and therefore increases activity of lytic enzymes

52
Q

What are the 5 lytic enzymes?

A

elastase, cathespin G, lysozyme, proteases, acid hydrolases

53
Q

What are the 2 cationic microbial peptides and what do they do?

A

defensins and cathelicidins. Function is interacting electrostatically with the negative membrane components therefore disrupting integrity of the microbial membrane

54
Q

What is the function of keratinocytes and muscosal epithelial cells?

A

express defensin genes, induced during auzurophil granule formation

55
Q

In what species is the gene for alpha defensin missing?

A

chickens, fish and livestock species

56
Q

What species has more cathelicidin genes than primates and chickens?

A

pigs

57
Q

What are the 6 functions of defensins?

A

disrupting microbial surfaces, chemoattractant for N, Ma, DC, Mo and fibroblasts, induce apoptosis of infeected host cells, anti-inflammatory by sequestering LPS and LTA, induce Ma cell degranulation, antiviral

58
Q

N extracellular traps (ETs) are released by?

A

dying N

59
Q

What are ETs composed of?

A

nuclear chromatin, histones, antimicrobial granule cargo

60
Q

Compare netosis and apoptosis

A

netosis involves NADPH-oxidase-mediated superoxide production and apoptosis involves caspases and DNA becomes fragmented

61
Q

How are N regulated during inflammation?

A

Secrete chemokines to attract Mo and chemotactic signals to attract Mo and DCs

62
Q

How do N directly activate DCs?

A

cell-cell contact through N CD11b ligation with DC-SIGN

63
Q

How do N direct immune response?

A

by producing IFNgamma therefore driving T-cell differentiation and M0 activation

64
Q

What doe N produce that promotes B cell survival?

A

BlgammaS

65
Q

How are N regulated during resolution?

A

By secreting pro-resolution molecules to terminate the influx of N and promote the influx of Mo

66
Q

What are the 3 pro-resolution molecules?

A

lipoxins, resolvins, protectins

67
Q

How are lipoxins generated?

A

from arachidonic acid using LOX

68
Q

How are resolvins and protectins generated?

A

from n-3 FAs by enzyme cascades: COX2, cytochrome P450 and LOX

69
Q

What do N produce to help against tissue damage?

A

IL-10

70
Q

What is the hallmark of inflammatory tissue resolution?

A

clearance of apoptitic neutrophils by M0 or mucosal surfaces

71
Q

N apoptosis is coordinated by what transcription factors?

A

hypoxia-inducible factor and FOXO3A

72
Q

What are N apoptosis “find me signals”?

A

Thrombospondin 1 which attracts M0s

73
Q

What are N apoptosis “eat me signals”?

A

lysophosphatidylcholine and phosphatidyserines which trigger scavenger-receptor mediated apoptosis

74
Q

Draw the N phagocytosis cascade

A

draw it

Comparative Immunology Midterm 2 (4 decks)

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