Haematopoiesis Flashcards
What stem cell do we first begin with before making blood cells
Haematopoetic stem cell
we start as a haemopoteic stem cells
- some are queiscece (not doing much)
- some are active and will grow into a progenitor cells and then into different cell types
Where does haematosis happen
in foetus and adult
Yolk sac, AGM, placenta, fetal liver
Adult
Bone marrow, in axial skeleton
in adults you can do haemotopoeiss in spleen and liver druing infection
also done in lymph nodes throughout
What two pathways does this stem cell take
It become a
-common myeloid progenitor
-common lymphoid
What cells are made from the common myeloid progenitor
-Monocytes
-Neutrophils
-Eoinsophils
-Basophils
-Red blood cells
-platlets (from megakaroytes)
What cells arise from the common lymphoid progenitor
- B cells
- T cells
- NK cells
Erythorcytes
What is the function of red blood cells
to carry oxygen
What is the structure of a red blood cell
-have a bioconcave shape (flexible, can pass through caps)
- No nucleus → so that they can have as much haemoglobin in it
- Colour comes from an iron-containing oxygen transport metalloprotein called haemoglobin in the cytoplasm
RBC
Lifespan?
120 days
Describe erthyrocyte development
-done via erythropoiesis
-Pronormobolast: large immature cells found in bone marrow → look like salami → have a blue cytoplasm
2. Normoblasts
3. Then after a few steps become a basophils (lots of RNA so stain blue)
-DNA matures and is broken down
-Folate and B12 used to make haem
4. Extrudes its nucelus
5. Becomes a reticulocyte, has no mitochondria, (sligty blue, sensitive to oxidative damaage) -> they also are flexible because of ankyrin and spectrin
if there’s a lack of folate and b12 you will make large RBCs
if theres
Where are red blood cells made
In bone marrow (they are called erthyroid islands, there’s macrophage)
How do we stimulate erythropoeissis
via hypoxia
What hormone stimulates erythropeoissis
where is it made
EPO
in kidneys
Describe how the kidney is involved in controlliing
-Circulating red blood cells leave the bone marrow and pick up oxygen in alveoli.
-Oxygen sensors in the kidney act the on the peritubular interstitial cells in outer cortex to make EPO.
EPO stimulates later stages of erythropoiesis
Epo given to people with kidney failure, since they may not be able to produce EPO
What cytokine determines wheher a cell is a red blood cell or platlet
GATA
Platlets
Function
to circulate to look at vascularlature
then when activated they stop blood flow via aggregation
Platlets
Where are they made
Parent cell made in bone marrow
Platlets
Lifespan
what are they removed by
8-12 days
removed by macrophages in spleen and liver
Describe the structure of platlets
name the granules and what they contain
- have no nucleus
- small discs
- Dense granules
-ADP and ATP (feedback molecules for platelet activation).
5-HT (serotonin) – can mediate vasocnstriction to stop bleeding
Polyphosphate - makes them electron dense activates the clotting system.: factor 12 reacts with these
Alpha garnules
Fibroingen VWF (involved haemostasis)
PF4 (chemokines)
-open canalicular system: allow platelets to spread
-microtubules: form round structure in cytoplasm to give platelets their round shape
-Dense tubular system: where intracellular calcium is stored. This calcium is released into the cytoplasm when platelets are activated.
What cell makes platlets
describe how it does ir as well
Megakaroycte
made in bone marrow
– they are large because their nuclei just divide, (so you get 2 nuclei, then 4 then 8 so they look bigger)
- cells then enlarge due to nuclear divisions (endomitosis)
- as they increase in size you get increased by
- eventually they get out into the bloodstream and expolde into many fragments
What hormone is involved in making platlets
where is it made and what does it do
TPO
-made in liver
-There is a TPO receptor (c-Mpl) on megakaryoblast, megakaryocyte and platelets → this will increase the amount of platelets
lack of TPO may lead to thrombocytopenia
Monocytes
What is the function of monocytes
Can migrate from blood into tissues and become macrophages
Key role is phagocytosis and cytokines
How long to monocytes live in blood
around 2 days in blood
Describe the shape of a macrophage
- Have a heart shaped nucleus
- smaller than neutropiols
- when they are in tissues they differentiate into tissues
- only see in injury and infection
What is the function of macrophages
-found in every organ of the body (for example alevolar macrophages, langerhan cells, kupher cells, microglia)
-can act as antigen presenting cells or phagocytoic cells
-importmat for surverying the enviorement
What cytokines do macrophages produce and what do they do
IL-12: Enhances the production of interferon-gamma (IFN-γ
-IL-12 also promotes diifernation and proliferation of T cells
IFN gamma: activates macrophages to increase phagocytosis
How long is the lifespan of a macrophage
some live for a few days during acute infection
-some live longer (tissue resisdent ones)
What transcrpition factor determines if a common myeloid turns into a monocyte
PU.1
What is the name of the three granulocytes
-Neutrophils
-Eosinophils
-Basophils
What is the function of neutrophils
neutrophils can..
1.Do phagocytosis
2.Makes NETs
3.Release cytokines, reactive oxygen species
4.Have strong antimicrobial activity
How long do Neutrophils survive
live about 2 days in blood
What is an neutrophil granules
rimary (azurophilic)
- Myeloperoxidase
- blech inside neutrophils good for killing pathogens
- Cathepsins, Defensins (break down cell walls)
- Lysozyme
- Elastase
Specific (secondary)
- Lactoferrin (inhibit iron, so microbes cant grow)
- Collagenase
Gelatinase (tertiary)
- Gelatinase
- MMP9
How do neutrophils kill stuff
-they do oxidative killing
- In phagosome you get full assembly of NADPH oxidase
- this forms superoxide anions, very toxic!!!!!!
- they act as substrate for super dismutase which makes another toxic substance called hydrogen peroxide
- and this acts as a substrate for MPO which makes hypochlorous acid aka bleach
- which kills the pathogen
How do neutrophils kill things that are bigger than them
NETosis
1.nuclar membrane breaks down
2.chromatin decondesnes
3.membrane ruptures
4.Neutrophils turn themselves inside-out when dying
5.NETs are sticky and can stop pathogens from moving
6.NETs are also full of toxic molecules and enzymes; damage cell walls and membranes to burst pathogen cells (which destroys them)
What is the function of eosinphils
can be involved parasite infections in gut, and mostly find them in bronchi (not phagocytic, release granules)
What cytokines do eosinophils secrete
they secrete
-Interleukin-4 (IL-4): stimulates B cell differentiation and antibody production, particularly of IgE
-Interleukin-5 (IL-5): promotes the growth, activation, and survival of eosinophils.
-Interleukin-13 (IL-13): involved in allergic responses and inflammation. contributes to tissue responses and can enhance mucus production.
- TNF-α
What is the function of basophlls
- found in your skin
- release granules
what granules do basophils secrete
-they contain histamine (inflammation mediator)
-heparin (prevents blood clotting)
Where do t cells grow (made)
Bone marrow
where do t cells mature
thymus
What are different T cell receptors
TCR beta , or TCR alpha
- some t cells recpetors have TCR gamma and TCR delta
How do we decide the diversity of T cell
Both heavy and light chains
Ig heavy chain: Variable, diversity, joining, constant
Ig light chain: Variable, joining, constant
some random combination happens, and you get a unique t cell
What do T cells need to see pathogens
-MHC
-the virus needs be taken by APC and presented via MHC to a T-cell
What syndrome causes a lack of t cells
Di Georges syndrome
Types of T cells
How does the T cell decide if it’s CD4 or CD8
During positive selection (the t cells that bind weakly are kept)
- if they recognise **MHC 2 **then they downregulate CD8 to become CD4 t cells
- if they recgnose **MHC 1 **they downregulate C4 to become CD8 t cells
orignallyhabe both CD4, CD8 receptors
How do naive t cells get activated
- naive t cells activated by antigens
- they expand and differnaite in lymph nodes
- they enter lymph nodes from blood,
- if they don’t encounter APCs they leave
- if they do encounter APCs, they proliferate and lose ability t exit lymph nodes for a bit
What receptor allows t cells to interact with lymph nodes
- CD62 ligand and CCR-7 allow the t cell interact with the lymph nodes endlithelim
- they tether
- they then get anchored by the ligand and CCR-7
- there’s a firm adehsion that allows them pass into endothelium into lympth
What three signals must naive T cells recieve from APCs to be activated T cells
- see cognitive antigen being presented by MHC, the t cell recogsies that
- get co-stimulatiry signal CD28 receptor reacts with B7.2 on the antigen cell
- cytokines determine what type t cell it differnates into
How do CD8 T cells kill
- they release of granules that contains perforin(makes holes in PM) and granzymes (released into target cell and drive apoptosis)
- FAS ligand on t cell interacts with FAS on target and causes apoptosis
How to T regulatory works
what recpetor do they express
-t regulatory express CD25
-they express fox P3 which unique to T reg cells
-express CTL4 which is like their break system
How they work
- produced inhibitory cytokines to dampen down immune response
- can compute for t cell growth factors like IL-2, so they can stop autoreactive t cells from getting IL-2 and getting activated
- they can also be contact dependent
Does CD4 or CD8 have more diversity
CD4
How many T helpers cell are there
TH1
TH2
TH17
TFH
TH1
What cytokines influences whether a t cell becomes t helper 1
Differentiate in the presence of IL-12
What do t helper 1 secrete
- ecrete IFNg when stimulated by antigen
- IFNg (interforean gamma) acts as a positive feedback loop to further
- enhance differentiation to a Th1 phenotype
- th1 express a specific TFs
What are the key functions of t helper 1
- promote immune responses against intracellaur bacteria
- involved in mycobacterial infections
TH-1 make IFN-g
- this stimulates infected macrophages to help control infection,
- by increasing:
- MHC expression
- Co-stimulatory molecule expression
- Nitric Oxide (NO) production
- Phagolysosome maturation
- TNF-a production
What autoimmune diseases are TH1 involved in
- Multiple Sclerosis
- Autoimmune thyroiditis
- Rheumatoid Arthritis
- Type I Diabetes
- Psoriasis
- Crohn’s Disease
- Allograft rejection
What do TH2 protect against
large extracellaur organisms, like parasites
How to t cells know to become a TH2
differnaiet from T cells into TH2 by IL-4
gata 3 helps you dismcinate from other t cells
What are the key functions fo TH2
- Th2 cells secrete IL-4, IL-5 and IL-13
- IL4,13 generate mucous and do peralstis (helps with removing worm)
- These act on effector cells including basophils, eosinophils and mast cells,
- help promote resistance to large extracellular helminth parasites
- eosinophils release granules to help break down large parasite
- mast cells same stuff grnaules
- IL-4 from Th2 cells promotes B cell class switching to IgE
What diseases are TH2 implicated in?
Th2 cells implicated in allergic and asthmatic disease
- Th2-derived cytokines can affect innate immune effectors in the airway
- musocus and pertalsis can happen in airways, feature of asthmatic response
- release of eiosnhipls and mast cells being driven by IL-5
How does a t cell decide to be a Th17 cell
what cytokines are involved
Th17 phenotype is stimulated by IL-1b, IL-6, IL-21, (TGFb) and maintained by IL-23
What is the function of T helper cells 17
- Promote activity of neurophils
-promote barrier intensity in small intestine and skin
-express the transcription factor RORgt and IL-17A/F, IL-22, CCL20 - Protect against fungal infection and some bacteria
- Increases neutrophil recruitment and controls epithelial barrier function
What dieases is Th17 implicated in
Multiple Sclerosis, Crohn’s Disease and UCs , Rheumatoid Arthritis
How does a T cell decide it wants to be a CD4+ T follicular cell
differentiation by IL-21
What is the functions of TFH cells
-TFH act within the secondary lymphoid compartment to help B cells
- help with isotype-switching antibody production
-Express the transcription factor Bcl-6
-Express the chemokine receptor CXCR5 to allow migration towards B cell areas where they can interact
- Co-express a wide range of Th phenotypes to allow appropriate B cell help
What is the function of t reg cells
supresses acvity of t cells
compete for Il-2
dampen immune response
Where can t reg cells differenate in the body
-Thymus
-periphery
What do periphery t reg cells need to differenate
pTReg differentiate in the presence of TGFb and retinoic acid
What transcription factor do t reg cells have
FoxP3
What are the functions of T reg cells
Functions
- consume cytoksines to stop them interacting with other t cells
- help cosumde il-2 which is needed for t cell growth
- Suppressive cytokine release (e.g. TGF-beta, IL-10, IL-35)
- Cytotoxic
- can kill other immune cells to suppress function
- Interact with antigen presenting cell
- this is to suppress function by using inhibitory signalling, removal of co-stimulatory molecules, cytotoxicity
- interact with CTLA-4 for example
What are the problems with T reg cells
-You can have hereditary deficiencies in fox-p3 (TF)
- develop autoimmune disease, anti-inflammatory
- T regs are involved when immune function is suppressed
- for example in tumor enviorments, there’s increases in t regs present which may be induced by cancer
What cell lineage do B cells come from
The common lymphoid progentitor
Why are B cells important
-there are some immune deficeinces that can affect antibody production
-children with antibody defects experience more disease
-lacking some antobodies like IgG increases susceptibility to some infections (can be rare, because children may not reach age where they can pass on their genes)
-cancers can be derived by B cells
-involved in the memory response
-roles in autoimmunity
-involved in vaccination (main aim is to make antibodies)
Where are foetal B cells made
Liver
What’s special about the b cell receptor
Only recognises one target, cuz its specfic
Why must we control B cell production
-so we make the approproate response for the pathogen
-so you don’t proudce self pathogens
-some b cells cant turn of proliferation, which can cause cancer
Give the overview of the life of a B cell
-make B cell
-make B cell receptor
-screen the B cell
-make a mature B cell
-can then become a plasma cell or a memory cell
What are antibodies made of
made of 2 heavy and light chains
-have two antigen binding sights
How do we develop the heavy and light chains
Done via rearrangment
Heavy chain
1.In stem cell: Germiline rearrangment
2.The D-J rearrangment in early pro B cells
3.In late pro B cells there is V-DJ rearrangment
4.in a large pre b cell there is a functional heavy chain
Light chain
1.In small pre B cell you do V-J rearrangements
2.In immature B cell you express IgM on the cell surface (VJ rearagneged)
3.You then express IgD which is made from alternaletly splcied H chains (mature B cell)
4. Helps mature. B cells leave bone marrow IgD
How do we test the functional heavy chain
you put it on he surface temporarly, to test if it can be there
We pair it with a light chain
If it works we go proliferation
The light chain goes through VJ rearrangement
How do we prevent further recombination of B cell
preventing RAG expression or function
B cell production can fail, so what do we do?
and what is the special name for this
- As humans we inherit many VDJCs
Rearrangements can occur from either inherited chromosome - BUT only one chromosome is used at a time
- if one fails, then you can use the other chrosmome
- You have 2 light chains, kappa and lambda to chose from
- two kappa genes are used first, then the two lambda genes
- this is called called allelic exclusion
ensures that one B cell produces antibody of one specificity
What is the kappa to lamda ratio in humans
3:1
if its different then can suggest that individual may have cancer
Since this process is random how do we select for the self reactive B cells
If the B cell is made recognises multivalent self-molecules, on bone marrow stroma cells, it will bind to them,
-sends a strong signal inside b cell -> leads to apoptosis .
soluble self-antigens floating in the body.
If immature b cell recognises these then it can become anergic (non-responsive) and dies via neglect
If no self-reaction and so the B cell migrates to periphery and go on to become full mature B cell.
What is the weakness of this process
Doesn’t account for intracelluar antiagens
- DNA and intracellular antigens are exposed
- intracellular antigens are the more important ones
- so… the b cells will be let of and they can do whatever really
How does the antibody response occur
what are the pathways
- t dependent
- t -independenat
What antibodies does the t independant pathway produce
IgM, soem IgG
these are low affinity ABs
What ABs does the t-dependent response produce
IgM , IgG, IgE, IgA
high affinity
memory
and long lived
Why is IgM called IgM
because it uses an IgM heavy chain
What is the first line of defence when it comes to ABs
IgM
What are the different concentrations of antibodies in the blood
- IgM and IgD expressed on surface of naive B cells
- igG - comes 1 to 4
- found in blood in conc 1 is found the most in blood compared to 4
- igA
- second highest concentration in blood
- there two forms
- IgE
- found in low levels in blood
- usually stuck on teh surface of cells (mast cells)
IgM can also be found in serum
Which antibodies can trigger the classical compliment pathway
IgG 1,2,3 and IgM
IgG 4 cannot do classical compleinent pathway
How are all teh IgGs different
- vary in structure
- influences function and how long they last for
- igG3 neck gives it a lot of flexibility due to high neck
- igG4 for worms
What ABs do mothers transfer
IgG 1 (highest level), 2,3,4
these help protect child for the first months of life (6 months)
Because it can cross the placenta
We
Which antibody has higha ffinity binding for mast cells and basophils
IgE
Describe teh shape of IgM and IgA
- igM , iGA pentamers and dimmers respectively
When ohm is secreted it joins 4 other Ugg, to make a l’entamer - influences how they can bind their targets
- by having 10 arms, it means it takes a lot to lose it
- think about monsetr in superhero film, hard to get rid of id they gave bare arms
What is the function of IgA
- igA is transported via epithelial cells via secretory component
- can help protect us in the lumen by binding and neutralise the target
- works to limit the activity of antigen at gut surface
Babies given IgA in breastmilk
what is the role of IgE
- usually bound to mast cells
- antigen gets in binds onto igE, causes an inflammatory reaction
Can cause muscus production, increase vascular permeability, can cause swelling, smooth muscle contraction
How to we catagories an antibodies
what three thinsg can they do
- opnisoation
-alerts immune system to remove it - neurtrolsaion
-prevent toxin from interacting with receptor and damaging cell - complement activation
What is the part of the antibody that binds to the antigen called
Epitope
remmeber ABs can have differnet shapes, and bind non covalenlty
How does having two arms help an antibodu
- because of two arms they can crosslink
- means they can form an immune complex
- sweeps up all the bad things aka bacteria, makes it easier for things to kill it
How do antibodies help in complmnt system
if done through compliment activation, you can punch holes in surface of bacertium, can lead to lysis and remenant can be vacumed off
-happens quicly
-c5-9 (MAK)
How do antibodies promote viral killing
- b can help promote killing of viral-infected cells
- pathogen-derived antigens (PAMPs) can be bound to host cell membrane
- Antibody can bind these antigens (i.e. infected cells)
- this enables immune cells like NK cells to target and kill the infected cell
- called antibody-dependent cellular cytotoxicity - ADCC
important for cancer and infected cells
How can antibody coated antigens be recognsied by cells
via FC gamma receptor
How are memory B cells developed and where
In germinal centre
1. GC B cells mutate and proliferate
2. How centroblasts in dark zone, has random point muataions within its Ig Variable reigon
3. this leaves the cycel, and becomes centrocytes
2. GC B cells need to recognise the OG antigen, so they compete for OG antigen on focilalr dentirc cells in light zone
3. then extra selection can you still talk to t cells and present the antigen to them
4. if recogntion goes ahead then T cells sends positive signals
4. if successful cells differneate into plasma cells and memory b cells
instead of making IgM you make IgG for better grip
For most cells it doesn’t happen, they go through apoptosis
those who win
- exit germnal centre to become plasma cells or memory b cells
- long live plasma cells live the bone marrow to live
What cells are involved in the making B memory cells
Centroblasts (Cb) – are proliferating GC B cells that undergo somatic hypermutation – dark zone
-introduction of random mutation
Centrocytes (Cc) – are GC B cells that have undergone affinity maturation and are out of cell cycle – light zone
- GC b cells with different names
Follicular Dendritic Cells (FDC) – These are different to iDC.
- They have intact antigen in its native conformation bound to their surface and Cc compete to bind this antigen in light zone
- don’t find them in T zone
- provides food for centrocytes to compete for
Follicular T helper cells
These are GC T cells that give survival signals to Cc after they come out of the dark zone – light zone
- give survival signs to centerocytes
What molecules are involed in making specific B cells
Activation-induced cytidine deaminase (AID) when expressed in B cells and is essential for class switch recombination and IgV hypermutation
B Cell Lymphoma-6 (BCL-6) is the master transcription factor for commitment of GC B cells and is required for the generation of TfH cells
CD40 on B cells and CD40L on T cells
IL21 is important for the generation of TfH cells
Blimp-1 is a transcription factor required for the plasma cell programme
Are NK cells part of the adpative immuen system
No, their recpetors do not undergo somatic hypermuation due to an antigen
How do we regulate NK cells
these have inhitory ior exictry receptors that are upregulated or downregulated
Do NK cells need MHC or antibody binding for an immune response
No, they have ablity to recgonise and kill cells
What is the main role of NK cells
Viral killing
Tumour survielance
How do NK cells kll
Have cytotoxic granules
- perforin and granzyme which allow allow for granule mediated apoptosis
Can do antibody-dependent cell-mediated cytotoxicity (ADCC)
Produce cytokines like
IFNγ and TNFα
If an NK cell does not see an mhc1 recpetor what does it do
it kills it (the cell)
What receptor helps on NK cells help recgonise antibodies
FCgamma R3 recepor
causes cytolytic granule release -> apotosis of cell
What part of the antibody binds the antigen
FAB
Fragment antigen binding
What is somatic hyper mutation
Happens in activated B cells
In spleen and germinal centres
Activated B cells express CD40 receptor
T cells with CD40 ligand interact
Helps up regulate b cells
T cell releases cytokines
Binds to cytokine receptors
Causes changes
For example AID is activated which is an enzyme this can do class switching from IgM to IgG etc
People who have an AID deficiency called hyperIgM immunodeficiency have a hard to switching from IgM to other ABs
What is affinity maturation
BCR with highest affinity to antigens live
It’s a bit like survival of the fittest
Due to somatic hypersomatisation
At the end of an immune response IgG binds onto FC Gamma 2 receptors to stop B cells with IgM to stop proliferating
This is because IgG has a higher affinity
What is the fragment constant
Decides what antibody it will be
What’s the difference between TCR and BCR
BCR
Has heavy chain, light chain, hast two FAB region and an FC
TCR
Has an alpha and beta chain
Only forms transmembrane receptor
Has one FAB sight
Do not get secreted
What part of VDJC determines the FAN region
Variable FAB
constant FC
What happens if B cells light chain is self reactive
It keeps rearranging the VJ, if it runs out of combos then it dies
What PAMPs is memory limited to and why
Memory response limited to peptide antigens seen by T cells
T indépendance antigens carbs and lipids don’t have memory b cells
What antibodies to memory B cells produce
Don’t produce IgM or IgD
They live for ten years though in lymph nodes
Tell me about t memory cells
T cells are sustained by IL-7
In the immune response IL-2 helps recruit more T cells
Once IL-2 secretion decreases the T cells die
Memory T cells have lots of IL-7 receptors which allows them to live for up to 25 years
Two types of t memory
Central T
Remain in lymphoid
Effector T memory
Look for antigen
