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Molecular Mechanisms > Myeloid Differentiation > Flashcards

Myeloid Differentiation Flashcards

1
Q

what is an epigenetic landscape?

A

where chromatin regulates which genes are turned on and off via transcription factors (TFs)
- TFs guide cell fate lineages

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2
Q

what do MEPs generate?

A
  • megakaryocytes –> platelets
  • erythrocytes
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3
Q

what do GMPs generate?

A

granulocytes

monocytes –> macrophages

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4
Q

what factors drive cell fate decisions?

A

extrinsic factors - molecules that are provided by other cells e.g. cytokines

intrinsic factors - transcription factors within cells

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5
Q

what is a cytokine?

A

class of soluble protein or peptides which act as humoral regulators by stimulating cell signalling and promoting developmental processes and cell maturation.
- can be pro or anti-inflammatory
- guide cell fate decisions
- highly potent - only nano-picomolars needed in concentration

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6
Q

how are cytokines classified?

A

interleukins - target leukocytes

chemokines - induce chemotaxis of cells

interferons - anti-viral immune responses

colony-stimulating factors - induce growth of lineage colonies

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7
Q

what are colony stimulating factors?

A

– induces growth of colonies in semi- solid methylcellulose medium – individual cells in solid matrix, but cannot diffuse, so proliferation forms a colony

  • Granulocyte colony is dense and small
  • Macrophage colony is looser and disperses
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8
Q

what are examples of colony stimulating factors?

A

Macrophage CSF (M-CSF) induces macrophages from progenitors

Addition of granulocyte CSF early enough will change progenitor cell fate from macrophage to granulocyte

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9
Q

what are examples of extrinsic signals for each cell fate lineage?

A

IL-3 = proliferation in all lineages, not specific

specific signals:
- TPO for platelets
- EPO for erythrocytes
- M-CSF for macrophages
- GM-CSF for GMP stage
- G-CSF for granulocytes

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10
Q

what are the producers and targets of stem cell factor (SCF)

A

producer: Bone marrow stromal cells

Targets: HSCs - maturation of haematopoietic lineages

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11
Q

what are the producers and targets of GM-CSF?

A

producers: T cells, macrophages, fibroblasts, endothelial cells

targets: Immature and committed progenitors, macrophages; granulocyte and monocyte differentiation, activation of macrophages

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12
Q

what are the producers and targets of M-CSF?

A

Producers: monocytes, endothelial cells, fibroblasts, mesangial cells

Targets: monocytes, macrophages

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13
Q

what are the producers and targets of IL-3?

A

producers: T cells

targets: immature progenitors - proliferation/maturation of all lineages

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14
Q

what are the producers and targets of IL-6?

A

producers: macrophages, endothelial cells, T cells

targets: proliferation of progenitors, neutrophils

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15
Q

what are the producers and targets of TPO?

A

producers: BM stromal cells, liver

targets: maturation of megakaryocytes and platelets

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16
Q

what are the producers and targets of EPO?

A

producers: eptihelial-like cells in renal cortex under hypoxic stress

targets: maturation of erythrocytes

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17
Q

what are type 1 cytokines?

A

IL-3, IL-5, IL-6, GM-CSF, G-CSF

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18
Q

how do type 1 cytokines signal?

A
  1. Cytokine receptor at PM
  2. When engaged with cytokine, phosphorylation of tyrosine with JAK kinase
  3. STATs activated by JAK enter nucleus and bind DNA motifs to promote expression of target genes involved in survival, proliferation, activation

Feedback loop to inactivate this pathway, ready for next round of activation

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19
Q

what are intrinsic signals of cell fate?

A

nuclear regulators: transcription factors (TFs)
- bind specific sequences of DNA (promoters or regulatory elements/enhancers)
- can bind alone or in complex with TFs
- induce co-activators and remodelling of chromatin to change transcriptional program
- most are activators some can be repressors

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20
Q

why does chromatin need to be remodelled? how does this happen?

A

Chromatin is wound around nucleosomes, so needs to be unwound and opened for TF access
- Promoters have multiple binding sites for multiple TFs – more specificity and activation
- remodelling complexes use ATP to remove nucleosome and enable access of 150 bp for TF binding

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21
Q

what intrinsic TFs are important for myeloid differentiation?

A

PU1 and GATA1 antagonise each other in the CMP progenitor
- GATA1 induces erythrocyte and megakaryocyte
- PU1 induces granulocyte/monocyte lineage

cEBP important for neutrophil development

GFli1 has inhibitory function

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22
Q

how do TFs guide lineage specification?

A

To become erythroid, need erythroid TFs to regulate erythroid genes
To become myeloid, need myeloid TFs to induce myeloid genes

TFs guide differentiation to become erythroid or myeloid cell

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23
Q

why must the extrinsic signals and TFs be balanced for myeloid differentiation?

A

There is overlap of what is required for different cell type
- Balance cytokines and TFs to guide cell fate decision
- Need to balance what cell types are produced as both populations are needed for survival – steady state

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24
Q

how can lineage fates respond to a depletion in red blood cells or low oxygen levels?

A

Need signals to repair problem:
More EPO production – more erythroid differentiation to erythrocytes

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25
Q

how do myeloid and erythroid TF signals antagonise each other to induce cell fate?

A

Myeloid TFs
- Need to reduce erythroid signal and boost myeloid
- Myeloid TFs have positive feedback, whilst inhibited erythroid TF

Erythroid TF
- Need to reduce myeloid signal and boost erythroid
- Erythorid TFs have positive feedback of TFs, whilst inhibiting myeloid TFs

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26
Q

what is PU.1?

A

transcription factor of the Ets family, which bind the core DNA sequence GGA(A/T)
- expressed in myeloid and lymphoid cells
- opposes the Meg/E lineage by binding to GATA-1 and repressing GATA-1 bound genes

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27
Q

in what cells is PU.1 expressed?

A

On in B cells
High expression in granulocytic and monocytic cells

Turned off in erythroid cells
Turned off in T cells

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28
Q

how has PU.1 been implicated in disease?

A
  • enhancer is an integration site for a virus which can increase PU.1 expression aberrantly –> erythroleukaemia
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29
Q

is PU.1 necessary for life?

A

yes - PU.1 K/O leads to mice dying as they lack myeloid, B and T cells

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30
Q

how can PU.1 expression be measured in cells?

A
  • GFP (green fluorescent protein) knocked into exon 1 of the PU.1 gene, resulting in a PU.1 heterozygous mouse PU.1 +/GFP
  • One allele is normal, other is tagged with GFP
  • Flow cytometry to see how much is in cells
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31
Q

what is the expression of PU.1 in cells of the haematopoietic lineage

A
  • LT-HSC and ST-HSC – some PU1
  • Myeloid and lymphoid have PU1
  • MEP lose PU1 as they mature – megakaryocyte and erythrocyte have no PU1 expression
  • GMP gain PU1 – high in granulocyte and monocyte
  • premature B cells maintain PU1 at low level, increases in mature B cells
  • T cell loses PU1 as it matures
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32
Q

what is PU.1’s effect on erythropoiesis?

A

acts negatively on erythropoiesis
- in PU.1 K/O mice there is a bias to erythroid phenotype - erythroid progenitors differentiate prematurely, leading to excessive apoptosis
- overexpression of PU.1 leads to anaemia due to a block of erythroid differentiation - accumulation of premature erythroblasts

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33
Q

how is PU.1 involved in regulating production of erythroid progenitors?

A

low PU.1 levels are important for proliferation of early erythroid progenitors

PU.1 must then be downregulated for terminal differentiation into red blood cells

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34
Q

what is the role of PU.1?

A

master regulator of myeloid differentation:
- Generation of monocytes and neutrophils is highly dependent on PU.1
- PU.1 is indispensible for CMPs differentiation to GMPs

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35
Q

how can PU.1 be studied in early differentiation stages from the from HSC progenitor?

A

induce PU.1 conditional knockout in bone marrow of adult mouse:
- leads to drop in HSC number
- loss of repopulation studies (bone marrow reconstitution assay)
- absence of CMPs and GMPs
- Controls have normal CMP and GMP,while PU1 K/O lacks these cells

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36
Q

how can PU.1 be studied in late differentiation stages from the from GMP progenitor?

A

Conditional K/O of PU.1 after GMP stage and sorted for CMPs or GMPs:
- colony forming potential of PU.1 deleted GMPs appears normal, however consists only of myeloblasts, no CD11b (maturation marker)
- colony forming potential of PU.1 deleted CMPs results in myeloblast colonies and MegE colonies

cells cant become granulocytes or monocytes anymore, only because myeloblasts or erythoid cells

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37
Q

what TFs dictate if a GMP becomes a macrophage or neutrophil?

A

PU.1 and C/EBPa
- neutrophil: C/EBPa increases, PU1 stays constant, Gfi-1 expression goes up
- Macrophage: PU1 is increased, C/EBP stays constant, EGR and NAB increases

antagonism:
- G-fi1 inhibits EGR and Nab to promote neutrophil
- EGR and Nab inhibits G-fli1 to promote macrophage

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38
Q

what is C/EBPa?

A

TF whihc binds CCAAT enhancer
- Expressed lowly in HSCs, then upregulated in granulocytes and monocytes
- C/EBPα -/- knockout mice die few hours after birth due to hepatic hypoglycemia
- Conditional C/EBPα -/- mice showed that the knockout blocks the transition from CMPs to GMPs
- C/EBPα and PU.1 levels determine the cell fate choice into macrophages or neutrophils

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39
Q

what is the network that drives macrophage vs neutrophil specification?

A

balance between PU.1 and C/EBPα determines the lineage fate

Secondary factors (Egr/Nab or Gfi-1) are reinforcing the establishment of each lineage

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40
Q

what is a PUER cell?

A

cell line generated from PU1 K/O mice – not viable but live during embryonic stage, CMPs in foetal liver can be obtained

PU.1-eostrogen receptor TF bound to ligand binding domain
- if nothing bound, it is in cytoplasm
- if bound to tamoxifen, it enters nucleus and becomes active to drive gene transcription and differentiation to macrophage or neutrophil

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41
Q

how do IL-3 and G-CSF affect macrophage/neutrophil differentiation via PU.1?

A

IL-3 induces proliferation of macrophages under PU.1 transcription

G-CSF skews towards neutrophils over macrophages, despite PU.1
- G-CSF enhances C/EBPa

extrinsic factor G-CSF and intrinsic PU.1 dictate final differentiation step between macrophage or neutrophil

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42
Q

how do extrinsic and intrinsic factors overlap in cell fate decisions?

A

cytokines modulate cell fate decisions by regulating lineage determining TFs

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43
Q

what is GATA1?

A

member of the GATA trancription factor family, which binds the DNA sequence GATA
- erythroid master regulator
- lowly expressed already in HSCs and CMPs
- essential for the development of erythrocytes and megakaryocytes
- GATA-1 knockout mice die during the embryonic stage E10.5 and E11.5 due to anemia
- regulator of the α- and β-globin genes, GATA-1 itself, Epo and EpoR (receptor)
- antagonizes PU.1 by displacing the co-activator c-Jun at its Ets domain

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44
Q

what complex does GATA1 recruit when it binds DNA?

A

GATA1 binds DNA and forms larger complex, SCL, E2A, Lmo2 bridging factor
– binds many specific DNA sites
– both elements needed for transcription
– more specificity

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45
Q

what are the interacting partners of GATA1?

A

GFI-1b
FOG-1
KLF-1
TAL-1/SCL

these complex with GATA1 to induce erythroid genes and stimulate erythrocyte proliferation

46
Q

what is GFI-1b?

A
  • repressor function in concert with LSD1-CoREST (demethylation of H3K4me and H3K9me)
  • repression of cell proliferation genes, e.g. myc and myb
47
Q

what is FOG-1?

A
  • interacts with MeCP1, a large, methylated DNA binding complex, including NuRD which promotes histone deacetylation
  • repressor function of genes maintaining the multipotential state and alternative lineage priming genes
48
Q

what is KLF1?

A

krueppel-like-factor 1
- Exclusively expressed in erythrocytes and their precursors
- KLF-1-/- mice die at E14.5 due to severe anemia
- KLF-1 acts primarily as an transcriptional activator
- Important for α- and β-globin synthesis as well as for heme synthesis and iron procurement
- Survival and proliferation of red blood cells

49
Q

what is TAL-1/SCL?

A

pentameric complex with LMO2, LBD1 and E2A
Activation of erythroid genes

50
Q

what does a master regulator mean?

A
  • Essential for specific lineage differentiation (k.o. models – lineage not produced or differentiation block)
  • Repress other potential lineage programs – antagonise each other
  • Able to direct or even change a specific cell program when introduced into cells
51
Q

how can conversion between cell lineages be studied?

A

Made library of TFs in retroviral construct which would infect T cells (marked with human CD4 tagged with GFP)
- Sequenced to see which viruses led to conversion of T cells into macrophages
- It was C/EBPa-positive viruses that did this

52
Q

why does lineage differentiation need to be so well regulated?

A

for example: LOF mutation in TF
- Block in differentiaton, so cells accumulate mutations which drive proliferation –> leukaemia
- Common in progenitor stages which proliferate often to produce many mature cells
- Mutation that stops differentiation in these stages will easily promote accumulation of progenitors

53
Q

what is the AML-ETO subtype of AML?

A

Translocation mutation between chr 8 and 10, induces fusion protein between DNA binding RUNX1 (AML1) and co-repressor ETO
- Interference with normal RUNX1 regulation leading to a block of granulopoiesis
- Second hit leads to transformation and high myeloblast counts
- Decrease of C/EBPα and PU.1 levels

54
Q

what is RUNX1?

A

TF which regulates C/EBPa and PU.1

55
Q

how can AML-ETO phenotype be rescued?

A

add C/EBPa back in using estrodial so it enters nucleus
- induces macrophage differentiation from the myeloid leukaemia cells

56
Q

what TF is commonly mutated in AML?

A

C/EBPa:
- Incomplete loss of function of C/EBPa
- frame-shift mutations, truncated products

Leucine zipper enables dimerisation for activation – mutations found here

Interestingly, C/EBPα knockouts don’t lead to leukaemia: aberrant C/EBPα contributes to transformation in leukaemia.

57
Q

what is decrease of PU.1 associated with?

A

Association of decreased PU.1 levels with myelodysplasia and AML

PU.1 has many enhancers
- If enhancer is lost, 30% reduction in PU.1 there is accumulation of immature cells,
- cells likely to develop into AML due to lack of differentiation stop and aberrant proliferation
- Mice with K/D of PU.1 have lower survival

58
Q

what happens to PU.1 levels in myelodysplastic syndrome? how is this overcome?

A

Reduced PU.1 levels in myelodysplastic syndrome (MDS)
- Methylation of CpG promoter inactivates PU1
- Demethylation increases expression of PU1

Combined demethylation and G-CSF causes shift from immature cells to more differentiated, mature cells to treat MDS patients and force cell maturation
- Chromatin is more accessible as DNA is no longer methylated

59
Q

what is innate immunity?

A
  • present at birth
  • induced by myeloid cells
  • not affected by prior contact - no memory
  • rapid response
  • recognises PAMPs via PRRs
  • limited diversity - germline encoded
60
Q

what is adaptive immunity?

A
  • developed over lifetime based on pathogen exposure
  • induced by T and B cells
  • generates memory
  • slower response - needs time to develop antibodies
  • antigen receptors with high specificity
  • highly diverse - somatic recombination - unlimited
61
Q

what are the general stages of an immune response?

A
  • site of microbe entry lined with macrophages
  • recognition and production of pro-inflammatory cytokines
  • recruitment of neutrophils/macrophages from bloodstream to engulf and kill pathogen
  • DCs/macrophages act as APCs to lymphocytes
  • soluble proteins like complement combat infection
  • macrophages induce tissue repair
62
Q

what are neutrophils?

A
  • most abundant
  • short-lived - 6 hrs
  • contains granules to digest pathogens
  • lysozyme, collagenase, elastase proteases
63
Q

what are mononuclear phagocytes?

A
  • granular cytoplasm with lysosomes and phagocytic vacuoles
  • broad range of PAMP recognition via PRRs
  • many subtypes
  • long-lived
  • can proliferate at site of infection
64
Q

what are the types of mononuclear phagocytes?

A
  1. monocytes - circulate in blood and can differentiate to inflammatory mature macrophages
  2. tissue-resident macrophages e.g. microglia, Kupffer cells
65
Q

what are the functions of phagocytes?

A
  • engulf microbes and apoptotic host cells
  • produce cytokines to instruct immune system
  • act as APC to T cells via MHCII presentation
  • tissue repair by stimulating angiogenesis
66
Q

what are mast cells?

A
  • found at skin and mucosal epithelia
  • FcyR for IgE
  • release granules containing cytokines and histamine once bound to antigen
  • defence against parasites
  • involved in allergy
67
Q

what are basophils?

A
  • circulate in blood
  • similar to mast cells
  • low in number
  • granular
68
Q

what are eosinophils?

A
  • increase in number upon inflammation
  • usually low numbers in peripheral tissues
  • granules contain enzymes to damage large parasites
69
Q

which cells are the main antigen presenting cells?

A

dendritic cells
macrophages
B cells

70
Q

what are APCs?

A
  • migrate to lymph node and stimulate T cells with 3 signals:
  1. present antigen-MHCII to TCR
  2. co-stim via CD80/86 to CD28 on T cell
  3. release cytokines to induce T cell differentiation
71
Q

what are dendritic cells?

A
  • main APC
  • phagocytic cell
  • recognise PAMPs via PRRs
  • conventional DCs migrate to lymph node to present antigen to T cells
  • plasmacytoid DC respond to viral infection via type 1 interferon production
72
Q

what are follicular dendritic cells?

A
  • present in germinal centres of lymph nodes, spleen and mucosal lymphoid tissues
  • present native antigens to B cells undergoing GC reaction
73
Q

how do leukocytes reach sites of inflammation/infection?

A

Interaction of leukocytes with the endothelial layer in the capillaries: adhesion molecules

also chemotactic gradients

74
Q

what adhesion molecules are involved in recruiting leukocytes from blood into tissues?

A
  1. P- and E- selectins expressed by active endothelium - bind to glycoproteins on leukocytes
    - L-selectin expressed on leukocytes - bind to sialomucin on endothelium
    - low affinity adhesion
  2. Integrins - cell-cell or cell-ECM adhesion for cytoskeletal signalling
    - LFA-1 and VLA-4 on leukocytes
    - ICAM-1 expressed on activated endothelial cells can bind MAC-1 on monocytes
    - high affinity
75
Q

how does valency control leukocyte docking onto endothelium?

A

Valency regulated by grouping of receptors on cell surface for improved docking site

76
Q

what are chemokines?

A

Family of structurally homologous cytokines (human: 50) which instruct movement of leukocytes
- produced by leukocytes, endothelial and epithelial cells, fibroblasts
- Chemokine secretion induced by microbe recognition and inflammatory cytokines
- induces cytoskeletal changes in cells for migration

77
Q

what are chemokine receptors?

A

Chemokine receptors are G-protein coupled receptors expressed on all leukocytes
- Signals transmit skeletal changes and increase integrin affinity
- regulate traffic of leukocytes through lymphoid tissues
- guidance of DCs from site of infection to the draining lymph nodes

78
Q

what is the process of leukocyte migration from blood to tissue?

A

Cell in blood and rolls on endothelial cells
- Selectins and ligands cause cell to slow down and arrest
- more interactions with integrins to cause flattening – increases adhesion
- cells will migrate through endothelial wall into underlying tissue

79
Q

what are the 2 ways in which leukocytes can pass through the endothelium to enter tissues?

A

Between two cells – paracellular

Transcellular – cell makes hole through endothelial cell, membrane gives way – not known if this truly happens

80
Q

what are PAMPs?

A

Pathogen-associated molecular patterns
- recognition of specific molecular structures of microbes that are highly conserved
- but number of recognized PAMPs limited

81
Q

what are DAMPs?

A

Damage-associated molecular patterns
- produced by cells damaged due to infection
- any injury to cells, e.g. chemicals, burns, trauma

82
Q

give examples of PAMPs in different pathogens:

A

bacteria:
- flagellin
- LPS (gram-negative)
- mannans
- CpG

fungi:
- dectin
- mannans

virus:
- ssRNA

83
Q

give examples of DAMPs:

A

heat shock proteins
HMGB1 - nuclear protein
histones

84
Q

how are PAMPs/DAMPs recognised?

A

Pattern recognition receptors (PRRs):
- germline encoded
- expressed by macrophages and neutrophils, DCs, epithelial and endothelial cells (barrier between the environment and the body) - these are likely to come into contact with pathogen
- can be extracellular or intracellular (cytosolic and endosomal)

85
Q

what are Toll-like receptors?

A

type of PRR:
- mostly on cell surface
- can be endosomal
- different TLR has different specificity
e.g. TLR4 = LPS, TLR3 = ssRNA

86
Q

What is the structure of TLRs?

A
  • leucine-rich repeats in PAMP-binding domain
  • TIR domains dimerise to induce signalling
  • depend on adaptors and co-receptors to form dimer
87
Q

what are the main adaptors and downstream effectors of TLRs?

A
  • Myd88 for all (except TLR3)
  • TRIF for all
  • induces MAPK pathway, IRF3
  • activates NF-KB to induce gene transcription and activate pro-inflammatory genes
88
Q

what do NF-kB and AP-1 induce?

A

Expression of inflammatory genes:
- cytokines (TNF, IL-1, IL-6)
- chemokines
- Endothelial adhesion molecules
- co-stimulatory molecules

induce acute inflammation

89
Q

what do interferon response factors (IRFs) induce?

A

Expression of type I interferon (IFNα/β) genes:
- secretion of IFNα/β

induce antiviral state

90
Q

what are cytosolic PRRs?

A

cytoplasmic PRRs detect infection in the cytoplasm where some bacteria escape to and viral particle assembly happens

e.g. NOD-like receptors, RIG-I-like receptors

91
Q

what are NOD-like receptors?

A
  • NLR-C: recognise bacterial cell wall components and toxins
  • signalling of NF-KB activation via RIP2 –> inflammation
  • NLR-P: activated by microbial products and cytoplasmic changes - inflammasome complex and secretion of IL-1b for inflammation
92
Q

what are the RIG-I-like receptors?

A
  • recognize ss and dsRNA
  • distinguish between viral RNA and cellular RNA
  • different specificities depending mostly on the length of dsRNA
  • binding of RNA results in activation of IRF3 and IRF7 or NF-κB depending on adapter molecules
  • induces antiviral state via type 1 interferons
92
Q

what is complement?

A

Proteolytic cascade of proteases activating downstream proteases thereby multiplying the effects of opsonizing and sometimes killing the microbe
- Serum proteins which complement innate immunity
- flags cells or bacteria to immune system or kill directly

93
Q

how does complement work?

A

Proteases C2, C3 and C4 are cleaved into two fragments
- Those fragments are the active components which start the pathway
- In all pathways, C3 needs to be cleaved
- C3a and C3B generated
- C5 is cleaved next, forms C5a C5b-9

94
Q

what are the activities of complement?

A

C3a and C5a act as chemoattractants for phagocyte recruitment

C3b induce opsonisation – phagocytes have C3 receptors to engulf an opsonised pathogen

C5b forms complex with other complement proteins to form MAC - forms pore in bacterium to induce cell lysis

95
Q

which cytokines can induce acute inflammation?

A

TNF

IL-1

IL-6

96
Q

what is TNF?

A

Tumour necrosis factor:
- produced by macrophages, DCs and others
- binds as trimer to a trimeric receptor
- cell signaling dependent of the IC domain of receptor, which induces apoptosis and cell death
activation of NF-κB and AP1 for inflammation

97
Q

what is IL-1?

A

Interleukin-1:
- produced by macrophages, neutrophils,
epithelial and endothelial cells
- binds IL-1 receptor (TIR domain)
- activation of NF-κB and AP1 - acute inflammation
- TLR and NOD signaling leads to IL-1 precursor synthesis
- NLRP3 inflammasome induces
maturation to active IL-1

98
Q

what is IL-6?

A

Interleukin-6:
- Produced by PAMP activated macrophages,
fibroblast, endothelial cells
- binds IL-6 receptor which signals via STAT3
- Stimulation of neutrophil generation in the BM for fast turnover

99
Q

what are the outcomes when TNF, IL-1 and IL-6 combine in function?

A

TNF and IL-1:
Activate endothelial cells by increasing their selectin and integrin expression

TNF, IL-1 and IL-6:
induction of acute phase proteins in the liver (C-type lectin, mannose-binding-protein, complement), fever

100
Q

what is IL-12?

A

cytokine which provides link to adaptive immune system:
- produced by macrophages and DCs
- stimulates IFN-γ production by NK cells and T cells
- enhances NK cell and cytotoxic T cell cytotoxicity
- promotes Th1 (T helper) cells differentiation
- acute inflammation to stimulate T cells

101
Q

what cytokines induce TH1 or TH17 CD4 differentiation?

A

APC produces different cytokines which induces differentiation of T cell subsets:
IL12 = TH1
TGFB, IL-6 = TH17, produces IL-17

102
Q

what are the two types of macrophage?

A

M1 - inflammatory

M2 - anti-inflammatory

103
Q

how are M1 macrophages induced?

A

IFNy and TLR ligands

104
Q

how are M2 macrophages induced?

A

IL-4, IL-13

105
Q

what are the functions of M1 macrophages?

A

destruction via ROS, NO, lysosomal enzymes - enhanced microbe killing via phagocytosis
- tissue damage

also induces acute inflammation via IL-1, IL-6 and IL-12
- anti-tumour immunity

106
Q

what are the functions of M2 macrophages?

A

anti-inflammatory response via IL-10 and TGFb - can aid tumour persistance

Fibrosis, tissue remodelling and angiogenesis
- produces proline polyamines, TGFb and VEGF

107
Q

how can innate immunity be regulated?

A

Negative feedback:
- TLR and cytokine signalling inhibitors
- IL-10 inhibits production of other cytokines IL-1, IL-12, TNF
- Autophagy genes to digest inflammasomes – reduces IL-1 response
- IL-1R agonist inhibits IL-1R
- Decoy receptors which mop up and sequester cytokines without downstream signalling

108
Q

how can inflammation be bad?

A

severe acute inflammation can cause septic shock:

Sepsis: when cytokines produced due to severe infection enter the blood stream and act systemic they cause organ damage and ultimately failure

109
Q

how can antibodies be involved in autoimmune diseases?

A

Autoimmune antibodies recognize host cells or tissue
→ activated leukocytes produce inflammation state and tissue damage

110
Q

what are examples of antibody-mediated autoimmune diseases?

A

autoimmune haemolytic anaemia
- targets erythocyte membrane proteins –> phagocytosis and lysis of red blood cells

Autoimmune thrombocytopenic purpura
- targets platelet membrane proteins
- opsonisation/ phagocytosis of platelets

Acute rheumatic fever:
- crossreaction of antibody from streptooccus to myocardial antigen
- inflammation

111
Q
A

Molecular Mechanisms (8 decks)

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