Hematopoiesis

Formation of blood cell - Hematopoiesis

1. Haematopoesis
Presented by-IPSITA SAHOO
Reg. no-200705180160
Supervised by-
Dr. SitaramSwain
Immunology and cancer Biology

2. CONTENTS
Haematopoiesis
Overview of Hematopoiesis
Site of Hematopoiesis
Hematopoietic stem cells (HSCs)and
types
Process of hematopoiesis
Regulation of Haematopoiesis
References

3. Haematopoiesisisdefinedastheprocessofformation,
developmentanddifferentiationofbloodcells.
Thebloodcellsareformedfromhaematopoieticstem
cells(HSCs)whichareeithermultipotentorpluripotent
innature.
Intheprenatalstage,haematopoiesisoccursintheyolk
sacduringthefirstweeksofembryonicdevelopmentand
transitionstothespleen,liver,lymphnodesandfinallyin
thebonemarrowcontinuingforlifetime.
Hemo–referring to blood cells
Poiesis-means the development or production of
Haematopoiesis
Hematopoiesisbegins during the first weeks of embryonic development.
All blood cells and plasma develop from astem cellthat can develop into
any other cell.
Facts of Hematopoiesis
Image credit-Kuby, immunology

4. Overview of Hematopoiesis
Image source-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3666375/

5. Site of Hematopoiesis
Image source-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3666375/

6. Haematopoieticstemcells(HSCs)arespecialtypeofcell
presentinthebonemarrow,theyarerareandtheirnumbersare
strictlycontrolledbyabalanceofcelldivision,death,and
differentiation.
HSCsdividegeneratingdaughtercells.Somedaughtercells
retainthestem-cellcharacteristicsofthemothercellhaving
propertyofselfself-renewingandabletogiverisetoallblood
celltypes.Whileotherdaughtercellsdifferentiateinto
progenitorcellthatlosetheirself-renewalcapacityandgiving
risetoaparticularbloodcelllineage.
Therefore,earlyinhematopoiesis,amultipotentstemcells
differentiatesalongoneoftwopathways,givingrisetoeither
acommonlymphoidprogenitorcellsoracommonmyeloid
progenitorcells.
Boththemyeloidandlymphoidlineagesareengagedin
dendriticcellformation.
Hematopoietic stem cells (HSCs)and types
Image credit-https://www.researchgate.net/figure/Hierarchical-division-of-the-stem-cell-in-hematopoiesis_fig1_316297048

7. Accordingtothemonophyletictheoryofhematopoiesis,thepluripotentstemcellsmultiplytoproducemoreofthe
pluripotentstemcells,makingsureofthesteadyandlastingsupplyofstemcells.Someofthepluripotentstemcells
nowdifferentiateintoprecursorcellsthatareleastpartiallydedicatedtoformonetypeofmaturebloodcell.
Pluripotentcellsmultiplyatlowpaceintooneofthefivepossibleunipotentialstemcells.
Theseunipotentialstemcellsthenmultiplyrapidlyintotheprecursorofthedestinedspecificmaturebloodcell.
Thetypicalprocessofhematopoiesisconsistsofthedifferentiationofthemultipotentialhematopoieticstemcellinto
eitherthecommonmyeloidorlymphoidprogenitor.
Then,relyinguponthecytokinesandresultingtranscriptionfactorsthatareactivated,themyeloidprogenitorcan
differentiateintoamyeloblast.
Thismyeloblastleadstogranulocyte(basophils,eosinophils,orneutrophils)ormonocyte(macrophagesanddendritic
cell)development.
Also,itleadstothedifferentiationofmegakaryocytesintoplatelets,orerythroblastsintoerythrocytes.
Lymphoiddendriticcellscanformdirectlyfromthecommonlymphoidprogenitor.
Furthermore,thedifferentiationofthecommonlymphoidprogenitorintoalymphoblastresultsthefurther
developmentofnaturalkillercellsorlymphocytes(TandBcells).
OnceBcellsgetactivatedinsecondarylymphoidorgans,itfurtherdifferentiateintoplasmacells.
Theseplasmacellssecreteantibodies.
Process of hematopoiesis

8. Process of Hematopoiesis
Myeloid cells:
It consists of-
Monocytes
Eosinophils
Basophils
Neutrophils
Macrophages
Erythrocytes
Megakaryocytes
Platelets.
Lymphoid cells:
It consists of-
B cells
T cells
Natural killer cells
Innate lymphoid
cells.
Image credit-Kuby, immunology

9. Hematopoiesisislargelyregulatedbythepresenceofcytokines.
Thesecytokinesareresponsibleforregulatingthedifferentiationofmultipotentialhematopoietic
stemcellsintospecificcelltypesbytheactivationoftranscriptionfactors.
Thecytokinesisveryimportantfordifferentiationofparticularcelltypesotherwiseanimaldies
duringembryogenesis.
Somecytokinesthatregulateshaematopoiesisare:
A.Granulocytemacrophage-colonystimulatingfactor(GM-CSF):
•Itenhancesthemyeloidlineage,finallyleadingtothedifferentiationofgranulocytesand
macrophages.Suchcytokinesaretermedasgrowthfactors.
•Thesegrowthfactorsareneededthroughouttheprocessofhematopoiesisfunctioningin
ordertoactivatetranscriptionfactors.
B.TranscriptionfactorGATA-2:
•Itisrequiredforthedevelopmentofallhematopoieticlineages;initsabsenceanimals
dieduringembryogenesis.
C.TranscriptionalregulatorBmi-1:
•Itisrequiredfortheself-renewalofHSCs,andinitsabsenceanimalsdiewithin2
monthsofbirthbecauseofthefailuretorepopulatetheirredandwhiteblood.
Regulation of Haematopoiesis

10. References
Jagannathan-Bogdan, M., & Zon, L. I.
(2013).Hematopoiesis.Development,140(12), 2463-2467.
Kuby, immunology.