Hematopoiesis Part 2 Flashcards
All blood cells are derived from single Pluripotent Hematopoietic Stem Cells
Most widely accepted
Monophyletic Theory
Pluripotent means
capable of self renewal, proliferation and differentiation
Each of the blood cell lineages is derived from its own unique stem cell
Polyphyletic Theory
capable of self-renewal
have a high-degree of proliferative capability
pluripotent
morphologically unrecognizable cells
give rise to differentiated progenitor cells
Noncommitted or Undifferentiated Hematopoietic Stem Cells
descendants of stem cells that can differentiate further into a specific cell lineage
morphologically unrecognizable cells
Committed or Differentiated Progenitor Cells
Two types of Multilineage-specific Progenitor Cells
- Commo Myeloid Progenitor
- Common Lymphoid Progenitor
Committed or Differentiated Progenitor Cells lineage
Multilineage progenitors → Unilineage progenitors → give rise to precursor cells
CFU-GEMM
Granulocyte, erythrocyte, megakaryocyte, monocyte
CFU-E
Erythrocyte
CFU-Meg
Megakaryocyte
CFU-M
Monocyte
CFU-GM
Granulocyte, Monocyte
CFU-Baso
Myeloid to basophil
CFU-Eo
Myeloid to eosinophil
CFU-G
Myeloid to neutrophil
CFU-pre-T
T lymphocyte
CFU-pre-B
B Lymphocyte
committed to forming a particular type of blood cell
morphologically recognizable cells
lineage-specific
Precursor Cells
MODEL OF HEMATOPOIESIS (Myeloid)
Pluripotent HSCs → Common Myeloid Progenitor → Granulocytic, Monocytic, Erythrocytic, Megakaryocytic Lineage
MODEL OF HEMATOPOIESIS (Lymphoid)
Pluripotent HSCs → Common Lymphoid Progenitor → T, B, NK-Lymphocytes, Dendritic Lineages
Stem Cell Marker - Lymphoid & Myeloid Precursors
CD 34
Stem Cell Marker - Committed Myeloid Progenitor
CD 33 & CD 38
Stem Cell Marker - Committed Lymphoid Progenitor
CD 10 & CD 38
Stem Cell Marker - T-lymphoid Progenitor cells
CD 7
Stem Cell Marker - B-lymphoid Progenitor Cells
CD 19
3 possible fates of Hematopoietic Stem Cells
Self-renewal
Differentiation
Apoptosis
Symmetric Division Lineage
HSCs divide → 2 identical daughter cells → both daughter cells leave the stem cell pool → undergo differentiation
Asymmetric Division Lineage
HSCs divide → 2 identical daughter cells → 1 daughter cell remains in the stem cell pool | 1 daughter cell leaves the stem cell pool → undergo differentiation or apoptosis
HSC randomly commits to self-renewal or differentiation
Stochastic Model (Till and McCulloch)
Microenvironment in the BM determines whether the HSC will self-renew or differentiate
Instructive Model
Initial decision: (THEORY)
HSC randomly commits to self-renewal or differentiation (Stochastic) → decision to proceed with lineage differentiation in the presence of various signals from the hematopoietic inductive microenvironment of the BM (Instructive) → cell differentiation and maturation occur
MORPHOLOGIC CHANGES THAT OCCUR AS CELL DIFFERENTIATES AND MATURES
Overall decrease in cell volume and decrease in the ratio of nucleus and cytoplasm (N:C ratio)
Changes in the nucleus
Changes in the cytoplasm
Changes in the NUCLEUS as cells DIFFERENTIATES and MATURES
Loss of nucleoli
↓ diameter of nucleus
Condensation of nuclear chromatin
Shape of nucleus
Loss of nucleus
Changes in the CYTOPLASM as cells DIFFERENTIATES and MATURES
↓ in basophilia
↑ proportion of cytoplasm
Possible appearance of granules in the cytoplasm
SIGNALS FROM THE HEMATOPOIETIC INDUCTIVE MICROENVIRONMENT
- Intrinsic Factors
- Extrinsic Factors
- Regulatory Signaling Factors
Intrinsic regulation involves ______
genes
TAL1 and GATA2 are essential for ____________
primitive and definitive hematopoiesis
(FACTORS)
expressed in the cells in the hemangioblast (bipotential progenitor cell of mesodermal origin)
TAL1
(FACTORS)
expressed in late-appearing HSCs
GATA2
Extrinsic regulation involves _______________
growth factors/cytokines
Allows HSCs to respond to hematopoietic inductive microenvironment
Notch-1
Notch-2
Regulatory Signaling Factors
group of specific glycoproteins that regulate the proliferation, differentiation and maturation of hematopoietic precursor cells
have stimulatory or inhibitory effects
Hematopoietic Growth Factors or Cytokines
Cytokines include:
interleukins (ILs), lymphokines, monokines, interferons, chemokines, and colony-stimulating factors (CSFs)
Cytokines that exert positive influence (stimulatory)
KIT ligand
FLT3 ligand
GM-CSF
IL-1
IL-3
IL-6
IL-11
Cytokines that exert negative influence (inhibitory)
Growth factor-β
Tumor necrosis factor-a
Interferons (gamma)
Roles of Cytokines
- Inhibits apoptosis
- Stimulate cells to divide by decreasing the transit time from G0 to G1 phase
- Regulate cell differentiation into various cell lineages
Programmed cell death
Natural physiologic process
Eliminates unwanted, abnormal or harmful cells
Apoptosis
When cells do not receive the appropriate cytokines necessary to prevent cell death,
__________ is initiated
apoptosis
they have the ability to induce hematopoietic colony formation
Colony-Stimulating Factors
stimulates formation of CFU-GM (colony-forming unit for granulocyte & monocyte/macrophage also known as Granulocyte-Monocyte Progenitor)
GM-CSF (Granulocyte-Macrophage Colony Stimulating Factor)
stimulates formation of CFU-M (colony-forming unit-monocyte)
M-CSF (Macrophage-Stimulating Factor)
stimulates formation of CFU-G (colony-forming unit-granulocyte)
G-CSF (Granulocyte-Stimulating Factor)
Receptor: KIT
KIT Ligand (Stem Cell Factor)
Receptor: FLT3
FLT3 Ligand
EARLY-ACTING MULTILINEAGE GROWTH FACTORS
KIT Ligand (Stem Cell Factor)
FLT3 Ligand
Protein molecules that have synergistic interactions with other cytokine to stimulate proliferation and differentiation of specific cell lines
Effective at very low concentrations
Interleukins
Erythropoiesis Lineage
Pluripotent HSC → Common Myeloid Progenitor/CFU-GEMM → BFU-E → CFU-E → Erythroid Precursor Cells → Mature erythrocytes
contains few receptors for EPO
Burst-Forming Unit – Erythroid (BFU-E)
contains many receptors for EPO
Colony-Forming Unit – Erythroid (CFU-E)
Lineage-specific glycoprotein hormone produced specifically by the peritubular interstitial cells of the kidney
A small amount of it is produced in the liver
Erythropoietin (EPO)
Stimulus for production and secretion of EPO: oxygen availability in the kidneys
↓ oxygen → ↑ EPO production
EPO Stimulates RBC production by:
- Recruitment of CFU-E from BFU-E
- Preventing apoptosis of erythroid progenitors
- Inducing hemoglobin synthesis
Two Major Categories of LEUKOPOIESIS
Myelopoiesis
Lymphopoiesis
production of monocytes and granulocytes (neutrophils, basophil, eosinophil)
Myelopoiesis
production of lymphocytes
Lymphopoiesis
MEGAKARYOPOIESIS Lineage
Pluripotent HSC → CMP/CFU-GEMM → Megakaryocyte progenitors (Burst-Forming Unit-Meg/BFU-Meg → CFU-Meg → Light Density-CFU-Meg/LD-CFU-Meg) → Precursor cells → Platelets