Hematopoiesis Flashcards
what are pluripotent stem cells
have ability to salvage all of the elements of hematopoiesis in recipient after the recipient’s bone marrow contents have been wiped out by irradiation or chemotherapy
morphologically what subset of cells do pluripotent stem cells belong to
blasts
how frequent are pleuripotent stem cells
less than 1 in 20 million
what are pleuripotenet stem cells criticl for
bone marrow transplant and gene therapy methods
how are bfu and cfu defined
responsiveness to handful of growth factors
what is TPO
thrombopoietin
what is EPO
erythropoietin
what are the percent of blasts
less than 4 percent
what percent is eryhtropoeisis
20-30
what percent is myelopoesis
60-70
what percent is lymphopoeisis
10-20
what are the stages of blasts maturing to neutrophils
blast to promyelocyte to myleocyte to metamyelocyte to bands and neutrophils
when in the maturation process do blasts lose ability to divide
when they are myelocytes
describe the number of mature species to less mature species as blasts mature
more matures ones than less mature ones
what is granulopoeisis termed
myelopoesis
what is a key regulator in granulopoeisis
GM-CSF and GCSF
what is difference in gmcsf and gcsf in blast maturation
gcsf acts primarily on neutrophils (gmcsf also acts on eosinophils)
what is maturation of blasts to erythroblasts
blast to pronormoblast to basophilic erythroblast to polychromatophilic erythroblast to normochromic erythroblast
what stimulates epo production
hypoxia sensed by renal peritubular cells
how many cell divisions in normal maturation of erythroid precursors
5
how are platelets produced
huge factory cells - megakaryocytes extend snakelike tubes (proplatelets) into highly fenestrated blood vessels in bone marrow (sinuses)
describe megakaryocytes
polyploid (not 2N but 16 to 32 haploid genomes) - nuclei divided multiple times
where does gmcsf come from
bone marrow stromal cells
where does gcsf come from
bone marrow stromal cells
where does epo come from
renal peritubular cells
where does tpo come from
hepatocytes
what does tpo regulate
blasts maturing to megakryocytes
where is tpo produced
hepatocytes at constant rate
what does a low platelet count allow tpo tp do
more tpo to bind to megakaryocytes stimulating thrombopoeisis
describe the epo and tpo receptors
transmembrane dimer with 2 copies of relatively inactive kinase attached to cytoplasmic tails
what is synonymous with tpo-r
cmpl
descibe how the jak-2kinase receptors work
binding of the cytokine to the receptor swings cytoplasmic tails together; kinases phosphorylate each other and then can phosphoylate other things downstream
how does bone marrow differ as you age
cellularity decreases
what are rhe requirments of red blood cell production
heme synthesis, globin synthesis, dna synthesis, regulation
what does heme synthesis require
iron, b6, succinyl coA, glycine
what does glycine require
b12 and folate
what does globin synthesis require
normal globin genes (alpha and beta) and amino acids
what does dna synthesis require
deoxynucleoside triphosphates
what do deoxynuceloside triphosphates require
ribonucleotide reductase and thymidine
what does thymidine require
b12 and folate
how is red blood cell production regulated
erythropoeitin
what does erythropoeitin require
normal kidneys and normal bone marrow micro environment
what are the 3 ways to become anemic
not making enough red blood cells, losing red blood cells from blood stream, or both
what does iron deficiency result in
cells without much hemoglobin
what is the appearance of an iron deficient rbc
smaller, center is large, hypochromic or microcytic
when will you see the terms anisocytosis and poikilocytosis
is a manual lab is done
what does anisocytosis mean
variation in size
what does poikilocytosis mean
variation in shape
what are anisocytosis and poikilocytosis characteristic of
severe anemia - but they are not specific
what will you see before anisocytosis and poikilocytosis in mild or moderate anemia
hypochromia
what is RDW
red cell distribution widthe- can get found using automated machine - red cell size distribution (if increased - correlated with morphologic anisocytosis
what can anemia suggest
iron def, but need other tests
what can microcytosis suggest
iron def but need more test
what can hypochromia suggest
iron def but need another test
what form is dietary iron typically
Fe3+, oxidized or ferric state
what form must iron be in to be taken up into the enterocytes
must be reduced to ferrous state Fe2+
how is iron converted from ferric to ferrous state
ascorbate used by duodenal cytochrome b (duodenal reductase)
what is ascrobate
plain old vitamin C
what is ascorbate turned into
dehydroascorbate
once taken up into the enterocytes what does iron need to do
be reoxidized for transport by serum oxidases
why must iron be transported with something
free iron would be a bad thing; augment bacterial growth and catalyze formation of superoxide radicals from oxygen
what handles iron transport in plasma
transferrin
what are the requirements for iron to be transferred by transferrin
must be ferric iron
what happens to transferring iron complex
turns over rapidly as it is take up by transferrin receptor on surface of RBC
because dietary iron might not be reliable, what does the body do
maintains an extensive reserve storage pool of iron in macrophages located in bone marrow, liver and spleen
what is iron bound to in storage in liver spleen and bone marrow
bound to ferritin
what transporters are involved in iron absorption in gut enterocytes
DMT-1 and ferroportin
what side is DMT-1 on
luminal memvrane
what side is ferroportin on
basement membrane
what regulates DMT-1 activity
iron dep regulation of its mRNA translation and stability
what regulates ferroportin activity
reg peptide called hepcidin
what is another role of ferroportin
export iron from macrophages that store iron
what are the two iron transport measurements that can be taken
iron transport system measurement and storage pool iron measurement
what are three ways to measure iron transport system
serum iron, total amount of transferrin in ciruclation and whether or not it is being utilized at full capacity or not
what is serum iron
direct measurement of transferrin bound iron
what is total transferrin in circulation also known as
total iron binding capacity
what is the term for whether or not the iron transport system is being utilized at full capacity or not
trasnferrin saturation
how do you calculate transferrin saturation
serum iron/transferrin
what is the way to measure storage pool iron
serum ferritin because trace amounts of ferritin from storage pool sites leak out into the serum and the concentration is proportional to the total amount in the pool
what is the most useful initial measurement of iron metabolism in patients with unexplained anemia
serum ferritin
what are the two ways iron deficiency can happen
increased red cell loss (usually some kind of chronic hemorrhage) or reduced dietary iron
in either cause of iron deficiency what is depleted
storage pool of iron
how can we detect a depletion in storage pool of iron
reduced serum ferritin levels
in most cases what happens when storage form iron is depleted and how can this be detected
move any remaining iron to bone marrow (ramp up production of transferrin); increased iron total binding capacity (TIBC)
in most cases, iron intake is not keeping up with iron utilization so what is reduced
serum iron
serum iron decreased means what
transferrin saturation is reduced
what happens to the transferrin receptors in iron deficiency and why
increase; iron starved macs increase amount of transferrin receptors on their surface
how can we measure the increase in transferrin receptors
soluble transferrin receptor measurement
if dietary iron goes down, what happens to storage form of iron
increased transfer of iron from the storage pool by an increase in ferroportin on macropahges in liver, bone marrow and spleen ; ferroportin in small bowel enterocytes is also increased in expression
where is hepcidin made
liver
what does hepcidin do
regulates iron uptake and transport
what is the expression of hepicidin linked to
amount of transferrin bound iron in the plasma
what does increasing amount of transferrin bound iron in plasma do to hepcidin
increases hepcidin production
what does hepcidin do to ferroportin
reduces ferroportin expression in macrophages and enterocytes (becomes internalized and degraded)
a disease process that increases hepcidin can result in what
anemia
what does the term thalassemia mean
reduced globin production
what do defects in the beta chain gene of globin produce
red cell appearance of small cells lacking hemoglobin
how do the cells differ between iron deficiency and thalassemia, usually
thalasemmia red cells are smaller with MCV of under 70 pL, and by showing target forms in the periphery
what is normal MCV
90 to 100 pL
what do target forms mean
nothing - not specific - can be thalasemmia but also can be with liver damage
what is the morphology of beta thalassemia
microcytosis, hypochromia (like iron deficiency); frequent target cells (nonspecific); can be severe if homozygous and can be mild and not clinically obvious if heterozygous
what is a reliable clue that your patient with microcytic anemia has thalassemia rather than iron deficiency
number of red cells
what are the number of red cells like in iron def
reduced
what are the number of red cells like in thalassemia
same or increased
what are your labs going to look like with thalassemia
microcytic anemia with increased or regular numbers of red cells
if you see microcytic anemia with increased or regular number of red cells, what do you need to order
hemoglobin electrophoresis test to confirm thalassemia
what does hemoglobin electrophoresis test detect
abnormal hemoglobin (hemoglobinopathies)
what chromosome is the beta globin locus on
chromosome 11
how many copies of the beta globin gene are on each copy of chromosome 11
6
what are the 6 copies of the beta globin gene
epsilon, g gamma, a gamma, psi beta, delta, and beta
what are the copies of the beta globin gene expressed in utero
epsilon, g gamma, and a gamma
what is psi betas function
pseudogene awaiting an evolutionary assignment
when is delta expressed
fetus with low expression after birth
when is beta expressed
after birth, in adults
what does normal hemoglobin look like
alpha2beta2 with traces of alpha2delta2
what happens if expression of beta globin gene is impaired by mutation
amounts of delta expressed increases
what is hemoglobin a
alpha2beta2
what is hemoglobin a2
alpha2delta2
what is fetal hemoglobin
alpha2gamma2
what is the type of hemoglobin seen most if patient has beta thalassemia
alpha2delta2 or hemoglobin a2
in severe cases of beta thalassemia what hemoglobin will be seen
hemoglobin f or alpha2gamma2 along with hemoglobin a2
what is hemoglobin f
alpha2gamma2, fetal hemoglobin
what determines the severity of different forms of beta thalssemia
mutation type and heterozygous vs homozygous
what is different about hemoglobin a and a2 in electrophoresis
a2 moves quite differently than a
what chromosome is the alpha gene locus on
chromosome 16
how many copies of the alpha gene are on each chromosome
4
what are the 4 copies of the alpha globin gene
zeta 2 zeta 1 alpha 2 alpha 1
which copies of the alpha globin gene are expressed in utero
zeta 2 and zeta1
which copies of the alpha globin gene are expressed in adulthood
alpha 2 alpha1
how many possible haplotypes are there for the alpha globin gene
4
how many possible genotypes for alpha globin gene are there
16, but only 10 functional
what is alpha thalassemia 1 trait
1 defective allele with almost no clinical findings
what is alpha thalassemia 2 trait
2 defective alleles
what do you see with alpha thalseemia 2trait
mild microcytic anemia, excess Hgb Barts (gamma)4 at birth, normal Hgb electrophoresis as adults
how do you diagnose alpha thalassemia 2 trait
PCR based (electrophoresis and/or sequencing)
what is epidemiology of alpha thalassemia 2 trait
3 percent of AA
what is alpha thalassemia with 3 defective alleles called
Hgb H disease (beta4)
what are the clinical findings in Hgb h disease
variable degree of microcytic anemia
what is the mechanism in Hgb H disease
excess of beta hemoglobin protein forms tetramer
how do you detect Hgb H disease
electrophoresis picks up tetramer
what can Hgb h disease be misdiagnosed as
iron deficiency
what is hgb barts
gamma4
what is seen in four defective alleles alpha thalassemia
hgb barts (gamma4); lethal in utero and soon after birth
what is epidemiology of four def alleles of alpha thalassemia
southeast asia
what must happen to ribonucleoside triphosphates for dna synthesis
reduced to deoxy form
what must happen to UTP for dna synthesis
must be methylated to TTP
what donates methyl groups in dna synthesis
folate derived donors
what is cobalamin
B12
what is the difference between thymidine and uracil
thymidine is uracil with methyl group added
how many different derivatives of folate take part in nnucleotide synthesis
2 - n10 formyl form and n5,n10 methenyl form
what does the n10 formyl form of folate take part in
purine synthesis
what does the n5,n10 metheynl form of folate take part in
thymidine synthesis
describe the process of purine synthesis
thee amino acids (gln, glu, and asp) come in with PRPP and n10formyl thf - you get purines (amp and gmp)
how do you get from thf to n10formyl thf
nadph and co2
what does a folate defiency result in
anemia bc you need folate to make dna which is needed for red blood cell synthesis
what is needed to convert homocysteine the methionine
b12 and n5methyl thf
what happens if you lack b12
all of your folate gets trapped in the n5 methyl form, making it unavailable for nucleotide synthesis; methyl trap hypothesis
what is intermediate between thf and n5 methyl thf
n5,10 methylene thf
when does methionine serve as methyl donor
after converted to s-adenosyl-methionine in the biosynthesis of a key component of myelin (sphingomyelin)
what does deficiency in b12 result in
anemia as well as characteristic neuro condition known as subacute combined degeneration of the spinal cord
what happens if you give folate supplementation to b12 def patient
worsens neuro conditions
can mammals make b12
no
how do mammals get all the b12 they can
Haptocorrin is first binding agent (protein in saliva) followed by binding of intrinsic factor binding b12 after hc is digested away in jejunum; IF brings it down distal ileum where complex enters blood
what makes instrinsic factor
parietal cells in stomach
what are ways in the pancreas that the b12 shuttle can fail
chronic pancreatitis
what are ways in the jejunum that the b12 shuttle can fail
bacterial overgrowth, parasites, sprue
what are ways in the ileum that the b12 shuttle can fail
ileum resection and crohns disease
what are ways in the food that the b12 shuttle can fail
b12 def food or breast milk
what are ways in the stomach that the b12 shuttle can fail
acid blockin drugs, atrophic gastritis, gastric bypass, partial or total gastrectomy, defect in intrinsic factor, pernicious anemia (lack of intrinsic factor)
what happens if you have impaired dna synthesis
fewer cells produced, normal/enhaced maturation of cytoplasm, and impaired nuclear maturation due to impaired dna synthesis
if dna synthesis is impaired where does the production line get held up
after one or two cell cycles where nucles is large but chromatin is not condensed down into darker material called heterochromatin
what happens to rna if dna synthesis is imparied
degraded and hemoglobins red color begins to predominate - megaloblastic appearance
what can cause megaloblastic anemia
impaired b12 uptake, impaired folate uptake, drug effect, intrinsic bone marrow dysfunction
what is the storage form of folate
linking it to series of glutamate residues (polygutamate residues)
what causes perncious anemia
impaired b12 uptake
what drugs can cause megaloblastic anemia
nucleoside analogues (HAART), and ribonucelotide reductase inhibitors (hyroxyurea)
red blood cell production is rgeulated by what
organs outside the bone marrow
what is a well known treatable consequence of renal failure
anemia
how is erythopoietin production regulated
oxygen sensors in peritubular cells in renal cortex
how do peritubular cells in renal cortex regulate erythropoietin production
when they sense low oxygen they secrete erythropoietin
what regulates the urge to breathe
co2 concentration in bloostream
what does chronic and acute inflammatory conditions do to hepcidin production and what is the consequence of this
increases it; impair utrilization of bone marrow iron stores as well as uptake or dietary iron (anemia of chronic inflammation if this happens long enough)
how does il-6 play a role in anemia of chronic inflammation
bacteria love iron; when you are undergoing infection it is good idea to hold onto your iron stores so Il-6 induces liver to make hepcidin
what happens to free transferrin in anemia of chronic disease
pulled out of ciruclation by hungry red cell precursors
what happens to transferrin saturation in anemia of chronic disease
increased
what happens to tibc in anemia of chronic disease
decreases
what happens to iron plus transferrin in plasma in anemia of chronic disease
decreases
what happens to ferritin in plasma in anemia of chronic disease
increases
what are signs of anemia of chronic disease
normocytic anemia, increased ferritin, reduced or normal serum iron, increased bone marrow iron stores
what infections, inflammation can cause anemia of chronic disease
aids, tb, rheumatoid arthritis, any cancer
