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Class notes Hemato-oncology (MS0469)
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HematoncologyThe blood:
- Plasma
- Cellular elements: red blood cells, white blood cells, platelets.
Only white blood cells have DNA and RNA → useful for
molecular diagnosis.
The white blood cells include lymphocytes, monocytes, neutrophils,
eosinophils, basophils.
All these blood cells are generated from hematopoietic stem cells.
The lymphocyte can be distinguished between B and T lymphocyte with
flow cytometry.
Complete blood count (CBD): give the number of all the blood cells,
concentration of hemoglobulin, dimension ecc:
- WBC/RBC: number of white/red blood cells
- Different percentage of the white blood cells: neutrophils, lymphocytes ecc
- ANC: absolute neutrophils count: WBC x % neutrophils
- ALC: absolute lymphocytes count: WBC x % lymphocytes (both B and T, for discriminate them we
need an analysis by cytometry, using antibodies specific for B or T antigens).
- AMC: absolute monocytes count: WBC x % monocytes
Terminology
Increase Decrease
Leukocyte leukocytosis leukopenia
Neutrophil neutrophilia neutropenia
Lymphocyte lymphocytosis lymphopenia
Monocyte monocytosis monocytopenia
Eosinophil Eosinophilia
Basophil Basophilia
Careful: neutrophila, lymphocytosis, monocytosis, eosinophilia and basophilia can be absolute or relative.
Life of mature cells
Myeloid:
- Granulo-monocytes: 10h (a few hours)
- RBC: 120 d
- platelets: 7-10 d
Lymphocyte: months/years. T cells stay there for a very long time.
Granulocytes have a very short lifespan. That means that you have to produce them continuously, to renew
the cells.
,If hematopoiesis stopped today because of a disease condition, would you expect that anemia precedes
thrombocytopenia? NO, because obviously became evident first the leak of platelets, which have a shorter
life span than RBC.
Es. Patient with a very important leukocytosis, but the differential count of white blood cells is not read by
the machine (**) → it is an algorithm, and the machine is not able to recognise neoplastic cells (that are not
scheduled in the algorithm). We can check them with microscope, because the neoplastic cells have a
morphology that is consistently different from the normal cells. The machine flag them with an asterisk
At the microscope we can see and identify these cells and is necessary do a peripheral blood smear.
- Red blood cells: do not contain DNA. They are not adequate for molecular diagnostics based on DNA
analysis.
- Granulocytes: they contain DNA in the multilobate nucleus. They have a granulated cytoplasm.
- Lymphocytes: round nucleus, scant cytoplasm. Not possible to distinguish B or T cells, we need a
cytometry.
- Monocytes: large kidney shaped or notched nucleus
- Platelets: fragment of the cytoplasm od the megakaryocytes. They are anucleate → they do not
contain DNA, ot good for molecular diagnosis.
Each second there are produced 2.3 million of red blood cells.
The blood cells factory is the bone marrow. It is a complex tissue:
- Bone: trabeculae, osteoblasts (produce cells), osteoclasts (destroy cells)
- Bone marrow: hematopoietic stem cells, vessels, extracellular matrix (is produced by cells but
outside), stromal cells (without it hematopoietic doesn’t work. Adipocytes, fibroblasts, macrophages,
mastocytes →interact with hematopoietic stem cells)
The bone marrow is composed of trabeculae (which is made of bone) and the bone marrow space where
occurs hematopoiesis.
We aspirate liquid blood from the bone marrow, then we stain that with May-Grunwald-Giemsa staining.
Where does our hematopoiesis reside? In the adult, the hematopoiesis occurs in flat bones. In child, also in
long bones.
,Bone marrow can be investigated:
- by aspirate: the needle passes through the cortical bone in which there is the spongy bone filled with
bone marrow. That can be analysed by cytometry, DNA extraction, smear of red bone blood ecc.
- biopsy (a piece of bone). The advantage of biopsy is that it is possible to investigate the architecture
of the tissue. It is not suitable for cytometry and not as good as aspirate. It is stained with
hematoxylin-eosin.
Hematopoiesis: a process of making blood from hematopoietic stem cells.
Formation and maturation of all BLOOD cells starting from the HSC and progenitor cells:
- proliferation of hematopoietic progenitors, whose pool is maintained by the HSC pool
- differentiation of hematopoietic progenitors into the differentiated cellular components of the blood
(precursors)
In normal cases, only the differentiated cells will pass over into the peripheral blood.
Pluripotential stem cells can generate all the blood cells. They can renew themselves and they are able to
orientate and differentiate in order to produce all the cells.
The properties of staminality decrease with increased differentiation. As HSC start to differentiate, they lose
in differentiative potential, lifespan and self-renewal.
Properties of HSC:
- self-renewal
- ability to differentiate
- capacity of regenerating the whole repertoire of the hematopoietic system
- undifferentiated cells
- resides at specific sites (hematopoietic niches)
- robust proliferative ability
- multipotent: capable of regenerating all hematopoietic compartments (myeloid, erythroid,
megakariocytic, lymphoid)
In basal conditions, most HSC are in the G0 phase of the cell cycle. According to the need, the proportion of
cycling HCS may increase in particular conditions and upon requirement.
HSC can’t be recognised by eyes. We need to check the antigen in the surface of the cells with flow cytometry
(CD) → CD34 (used in clinical diagnosis)
Hematopoietic microenvironment: environment of cells
, It is composed by mesenchymal and hematopoietic cells that provide a physical and biochemical support to
the hematopoiesis through:
• Cell-cell surface interactions: cell interact with molecules on the surface of the other cells
• Interactions with extracellular matrix: provide signals to hematopoietic stem cells and to progenitals
• Soluble factors: stromal cells send messages through cytokines and growth factors.
It is a continuous dialog between HSC and microenvironment through these 3 different signals.
Hematopoietic stem cell niches
HSC do not circulate because they are strongly attached to the niches in bone marrow.
We can identify two main types of niches:
1. Endosteal niche, in which the main cells of the niche are osteoblast.
2. Vascular niche in which there are sinusoid endothelial cells.
HSC in G0 phase are localized mainly in the endosteal niche, in a dormient state. Instead, the activated HSC
reside mainly in the proximity of the vascular niche, then they will undergo differentiation and proliferation
to give rise to the terminal differentiated blood cells.
HSC can migrate from one niche to the other. For example, G-CSF stimulate HSC to leave the endosteal niche
and be activated in vascular niche.
Growth factors:
1. Control proliferation and differentiation of HSC and progenitor cells
2. Many are termed CSF (Colony-stimulating factors) because they are required, in vitro, for the
development of progenitor cells from the HSC
3. Produced mainly by stromal cells: lymphocytes, monocytes, macrophages, endothelial cells and
fibroblasts
Erythropoietin induces an erythropoietic differentiation
Thrombopoietin → differentiation of megakaryocyte
G-CSF (granulocyte colony stimulating factor) → myelopoiesis, differentiation of granulocytes.
There are recombinant drugs of these growth factors, to stimulate the differentiation. Es. rhG-CSF for
neutrophil production. In high concentration of G-CSF the process of differentiation became shorter.
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