5. Erythropoiesis Flashcards
The term for RBC formation
Erythropoiesis
Total mass of RBCs circulating in the peripheral blood and the bone marrow RBC precursors.
Erythron
Erythrocytes in the circulation
RBC mass
A term that describes the dynamics of RBC creation and destruction
Erythrokinetics
Production of defective erythroid precursors
Ineffective erythropoiesis
2 examples of macrocytic, normochromic anemias caused by ineffective erythropoiesis
folate deficiency
vitamin b12 deficiency
Ineffective erythropoiesis causes defective RBC precursor cells to undergo _____ in the bone marrow before they even mature to the reticulocyte cells.
apoptosis
2 examples of microcytic, hypochromic anemias due to ineffective erythropoiesis
thalassemia
sideroblastic anemia
Decrease in the number of RBC precursors in the bone marrow resulting in decreased RBC production
insufficient erythropoiesis
what type of anemia is iron deficiency
microcytic, hypochromic
type of anemia of acute leukemia and renal disease
normocytic, normochromic
examples of conditions that resulted from insufficient erythropoiesis
iron deficiency anemia
acute leukemia
renal disease
immature hematopoietic stem cells that is committed to a cell line but cannot be identified morphologically
progenitor cells
immature HSCs that are morphologically identifiable or belonging to a given cell line
immature HSCs that are morphologically identifiable or belonging to a given cell line
precursor cells
a transferrin receptor and also the earliest marker of erythroid differentiation
CD71
progenitor vs precursor
progenitor: morphologically unidentifiable
precursor: morphologically identifiable
How to measure RBC Survival
- Collect px blood sample
- Label RBCs with Chromium-51
- Inactivate excess Chromium-51 in plasma
- Reinject labeled RBCs to px
- Measure radioactivity of RBCs at intervals until 50% of activity has disappeared
The results for RBC survival are commonly expressed as
Chromium-51 half-survival time
Normal range for RBC survival range
28-38 days
Chief stimulatory cytokine for RBCs
Erythropoietin
EPO is the major hormone that stimulates the production of _____
RBCs
T/F
EPO is a thermolabile, dialyzable, glycoprotein hormone
False. Thermostable and non-dialyzable
Primary cell source of EPO
peritubular interstitial cells of the kidneys
primary target cells of EPO
BFU-E
CFU-E
Normally, EPO is released into the blood in response to
hypoxia
3 major effects of EPO
- early release of reticulocytes from BM
- reduce time needed for RBCs to mature in BM
- prevent apoptotic cell death
apoptosis rescue by EPO is the major way of increasing
RBC mass
Blood doping can lead to
deadly arterial and venous thrombosis
Illegally done by some athletes; done by using EPO injections to increase the oxygen-carrying capacity of their body
Blood doping
Blood doping is illegally done by some athletes to increase
stamina and endurance
Growth hormone and prolactin are released by
pituitary gland
Growth hormone and prolactin stimulates erythropoiesis _______
directly
Testosterone is released by the
testes
Estrogen is released by the
ovaries
estrogen inhibits erythropoiesis ______
indirectly
testosterone stimulates erythropoiesis _______
indirectly
This is the reason why men have higher threshold values for Hgb, Hct, and RBC count.
Men have testosterone. Testosterone stimulates erythropoiesis.
Women have estrogen. Estrogen inhibits erythropoiesis.
T/F
Menstruation is the main reason why women have lower threshold values for Hct, Hgb, and RBC count.
False
committed erythroid progenitor cells
BFU-E
CFU-E
BFU-E means
burst forming unit-erythroid
CFU-E means
colony forming unit-erythroid
How long does it take for the BFU-E to mature to an erythrocyte
18-21 days
____ are spent as recognizable precursor in the BM
6 days
Rubri nomenclature
Rubriblast-Prorubricyte-Rubricyte-Metarubricyte-Reticulocyte-Mature RBC
Normoblast nomenclature
Pronormoblast
Basophilic normoblast
Polychromatophilic normoblast
Orthochromatic normoblast
Reticulocyte
Mature RBC
Erythroblast nomenclature
Proerythroblast
Basophilic erythroblast
Polychromatophilic erythroblast
Orthochromatic erythroblast
Reticulocyte
Mature RBC
When reticulocytes are found in a wright-stained smear, they are called
polychromatophilic erythrocytes
diffusely basophilic erythrocytes
When diffusely basophilic erythrocytes are found using a supravital stain, they are called
reticulocytes
Rubriblast is also called
Pronormoblast
Proerythroblast
Rubriblast size
12-20 um
Number of nucleoli of rubriblast
1-2
rubriblast n:c ratio
8:1
a morphologic feature used to identify and stage RBC and WBC precursors; also a visual estimate of what area of the cell is occupied by the nucleus compared with the cytoplasm
n:c ratio
Rubriblast gives rise to
2 prorubricytes
The earliest recognizable RBC precursor using light microscope
Rubriblast/Pronormoblast/Proerythroblast
If the areas occupied by the nucleus and the cytoplasm are approximately equal, the N:C ratio is
1:1
If the nucleus takes up <50% of the area of the cell, the ratio is
lower
If the nucleus takes up >50% of the area of the cell, the ratio is
higher
refers to the blue part of the cell and is due to the acidic components
basophilic
refers to the pink part of the cell and is due to the basic components
Acidophilic
the degree of cytoplasmic basophilia correlates with the quantity of
ribosomal RNA
As the RBC matures, the eosinophilia of the cytoplasm correlates with the accumulation of
hemoglobin
Prorubricyte other names
Basophilic Normoblast
Early Normoblast
Basophilic Erythroblast
Early Erythroblast
size of prorubricyte
10-15 um
of nucleoli of early normoblast
0-1
N:C ratio of Basophilic Erythroblast
6:1
Most helpful criteria in distinguishing early normoblast from proerythroblast
coarser chromatin
absent nucleoli
Basophilic normoblast is the last stage with a
nucleolus
Prorubricyte is the first stage of
hemoglobinization
Rubricyte other names
Polychromatophilic normoblast
Intermediate normoblast
Polychromatophilic erythroblast
Intermediate Erythroblast
Intermediate normoblast size
10-12 um
of nucleolus of intermediate erythroblast
0
N:C ratio of Polychromatophilic normoblast
4:1
The prorubricyte gives rise to
4 rubricytes
Each rubricyte gives rise to
2 metarubricytes
What RBC precursor is commonly confused with lymphocyte
Polychromatic normoblast
lymphocyte vs rubricyte
Lym nucleus: crushed velvet; cytoplasm: sky blue, “robin’s egg” blue
Rubricyte nucleus: checkerboard; cytoplasm: muddy/gray
This RBC precursor is the last stage to undergo mitosis
Intermediate erythroblast
The first stage where the pink color caused by recent hemoglobinization first manifests
Rubricyte
Metarubricyte other names
Orthochromatic normoblast
Late normoblast
Acidophilic normoblast
Orthochromatic erythroblast
Late erythroblast
Pyknotic erythroblast
Nucleated red blood cells
The nucleus is _____ during the pyknotic erythroblast phase
extruded
Last RBC precursor to have a nucleus
Acidophilic normoblast
size of late erythroblast
8-10 um
of nucleolus of late normoblast
0
color of orthochromatic erythroblast’s cytoplasm
salmon-pink
N:C ratio of Orthochromatic normoblast
1:2
Enveloped extruded nucleus engulfed by bone marrow macrophages
pyrenocyte
Frequently, small fragments of the nucleus are left behind if the nRBC projection is pinched off before the entire nucleus is enveloped. These small fragments are called
Howell-Jolly bodies
Howell-Jolly bodies are removed from the RBCs by the spleen thru
pitting
Young RBCs containing residual RNA
Reticulocyte
size of reticulocyte
8-10 um
What RBC precursor has the same size?
Metarubricyte
Reticulocyte
of nucleolus of reticulocyte
0
T/F
Reticulocyte has a nucleus
False
Last immature erythrocyte stage
Reticulocyte
Reticulocytes spend _____ in the bone marrow and ____ in the peripheral blood before developing into a mature RBC
2-3 days
1 day
2 types of reticulocytes
shift cells
stress reticulocytes
These reticulocytes are seen in cases with increased RBC production.
Shift cells/polychromatophilic macrocyte
These reticulocytes are seen in severe conditions like hemolytic anemia
Stress reticulocytes/ Macroreticulocytes
The last stage of hemoglobin synthesis
Reticulocytes
Reticulocyte count is used to diagnose the type of _____ present in a patient
anemia
size of mature rbc
7-8 um
shape of mature rbc
biconcave disk
thickness of rbc
1.5-2.5 um
Average life span of rbc
120 days
number of rbcs produced from 1 rubriblast
16
Normal ratio of RBCs to WBCs
600:1
Normal ratio of RBCs to platelets
15:1
Adult RBC contains no mitochondria, therefore there is no
protein, hemoglobin synthesis
Central pallor of mature RBC occupies ____ of the cell’s diameter1
1/3
Major macromolecule that constitutes the RBC membrane
Proteins (peripheral and integral) 52%
Other RBC constituents aside from proteins
lipids 40%
CHO 8%
Provides the vertical support connecting the bilayer to the underlying cytoskeleton to maintain RBC membrane integrity
transmembrane proteins
An integral protein that transports water
Auaporin 1
An integral protein that transports anion and supports ABH antigens
Band 3
Ca2+-ATPase transports
Ca2+
Supports Fy antigen
Duffy
Glucose transporter and supports ABH antigen
Glut-1
Transports negatively charged sialic acid (3)
Glycophorin A
Glycophorin B
Glycophorin C
Different functions of 3 integral proteins that transports negatively charged sialic acid
GA: supports MN determinants
GB: supports Ss determinants
GC: supports Gerbich system determinants
a transmembrane protein that is responsible for integrin adhesion
ICAM-4
Zn2+-binding peptidase, K antigens
Kell
Integral protein Jk transports
urea
D and CcEe antigens
Rh
D and CcEe antigens
Rh
This is necessary for expression of D and CcEe antigens, also transports gas i.e. CO2
RhAG
Proteins that provide the horizontal support for the membrane.
Skeletal/Cytoskeletal/Peripheral Proteins
The shape and flexibility of the RBC depends on the
cytoskeleton
primary skeletal proteins
a-spectrin
b-spectrin
caps actin filament
adducin
tropomodulin
Ankyrin anchors (2)
band 3 and protein 4.2
actin building protein
dematin
F-actin binds
b-spectrin
anchors 4.1 complex
protein 4.1
protein 4.2 anchors
ankyrin complex
regulates actin polymerization
tropomyosin
Defect in protein(s) that disturbs vertical membrane interactions between transmembrane proteins and underlying cytoskeleton; loss of membrane and decreased surface area-to-volume ratio.
Heredirary Spherocytosis
Inheritance pattern of hereditary spherocytosis
autosomal dominant
deficient proteins in hereditary spherocytosis (5)
ankyrin
band 3
a-spectrin
b-spectrin
protein 4.2
this rbc index is elevated in hereditary spherocytosis
Mean Corpuscular Hgb Concentration
Normal MCHC range
31-37 g/dL
MCHC of px with HS
35-38 g/dL
What is the only disease that is characterized by high MCHC?
Hereditary Spherocytosis
T/F
In HS px, the rbc membrane is elastic, but is less stretchable
FALSE.
stretchable, less elastic
Spherocytes gather this electrolyte( ?) at a higher rate than normal RBCs in the spleen; leading to a decreased tolerance to osmotic changes because they —- then lyse.
Na
swell
What surgical procedure is beneficial to px with HS
splenectomy
Most sensitive and specific test to confirm the diagnosis of HS
Eosin-5′-maleimide (EMA) binding test
principle of EMA binding test
flow cytometry
Defect in proteins that destroy the horizontal linkages in the protein cytoskeleton which results to the loss of mechanical stability of membrane
Hereditary elliptocytosis
Inheritance pattern of hereditary spherocytosis
Autosomal dominant
deficient proteins in HE (3)
a-spectrin
b-spectrin
Protein 4.1
A rare subtype of hereditary elliptocytosis that has an autosomal recessive pattern
Hereditary pyropoikilocytosis
deficient proteins in hereditary pyropoikilocytosis
a-spectrin
b-spectrin
Severe defect in spectrin the disrupts horizontal linkages in protein cytoskeleton; severe RBC fragmentation
Hereditary pyropoikilocytosis
Hereditary ovalocytosis is also known as
Southeast Asian ovalocytosis
inheritance pattern of hereditary ovalocytosis
autosomal dominant
defective protein in southeast asian ovalocytosis
band 3
Defect in band 3 causing increased membrane rigidity; resistant to malaria; prevalent in some areas of SEA
hereditary ovalocytosis
Overhydrated hereditary stomatocytosis causes increased membrane permeability to
Na
K
hereditary pattern of overhydrated hereditary stomatocytosis
autosomal dominant
deficient proteins in overhydrated hereditary stomatocytosis
Rh-associated protein (RHAG)
others unknown
In OHS increased intracellular Na causes influx of H2O, increase in cell volume, and decreased cytoplasmic viscosity. This further results to what RBC morphology
stomatocytes (5-50%)
macrocytes
The most common form of stomatocytosis
Dehydrated hereditary stomatocytosis
Dehydrated hereditary stomatocytosis is also known as
Hereditary Xerocytosis
Inheritance pattern of hereditary xerocytosis
autosomal dominant
deficient protein in hereditary xerocytosis
piezo-type mechanosensitive ion channel component 1
In HX, there is increased permeability to (ELEC?) leading to a decrease in this intracellular electrolyte
K
A decrease in intracellular K results to
loss of water from cell
decrease in cell volume
increased cytoplasmic viscosity
Typical RBC morphology in HX
Codocytes
Burr cells
Stomatocytes (<10%)
RBCs with puddled Hgb at periphery
dessicated cells with spicules
HS, HE, HP, HO/SEAHO are caused by mutations that change
membrane structure
OHS, DHS/HX are caused by mutations that change
membrane transport proteins