Cytokines and Hematopoiesis

Question 1

compare/contrast blood collected with/without anticoagulant

Answer 1

uncoagulated: consists of plasma with fibrinogen, buffy coat (leukocytes and platelets, 1%) and RBCs (42-47%)
coagulated: consists of serum and clotted blood with fibrin

Question 2

describe process of erythropoiesis

Answer 2

occurs in bone marrow
maturation within blood stream
1) HSC
2) CMP - induced by EPO, IL-3 and IL-4
3) Megakaryocyte/Erythrocyte Progenitor (MEP)
4) Erythrocyte-Committed Progenitor (ErP)
5) Proerythroblast - immature but fully committed to pathway; basophilic staining
6) Basophilic Erythroblast - basophilic staining
7) Polychromatophilic Erythroblast - basophilic (ribosomes) and acidophilic (hemoglobin) staining
8) Orthochromatophilic Erythroblast/Normoblast - acidophilic staining; dense nucleus ready to be extruded
9) Reticulocyte - anucleate, polychromatophilic, 1-2% of circulating RBCs; level can tell us how much erythropoiesis is occurring
10) Erythrocyte

Question 3

describe locations of hematopoiesis during development

Answer 3

week 3 - 2T: yolk sac
2T: liver; WBCs begin forming
2T - adulthood: bone marrow; becomes primary site in 3T

Question 4

general trends of hematopoiesis

Answer 4

1) cell diameter decreases
2) cytoplasm becomes less basophilic
3) hemoglobin deposition imparts pink color
4) nucleus:cytoplasm decreases
5) nuclear color changes: purplish red -> dark blue
6) nuclear chromatin condenses

Question 5

stem cell factor (C-Kit ligand)

Answer 5

produced by bone marrow stromal cells

induces self-renewal and differentiation

Question 6

c-kit receptor

Answer 6

expressed by hematopoietic stem cell (HSC)
tyrosine kinase receptor (MAPK, PI3-K, Jak/STAT)
proto-oncogene

Question 7

common myeloid progenitor cells (CMP) produce?

Answer 7

give rise to RBCs, leukocytes, and platelets

Question 8

common lymphoid progenitor cells (CLP) produce?

Answer 8

give rise to B cells, T cells, and natural killer cells

Question 9

erythrocytes - properties

Answer 9

anucleate
biconcave
contain plasma membrane, cytoskeleton, hemoglobin and glycolytic enzymes
live for ~120 days

Question 10

compare/contrast ABO blood types

Answer 10

type O: standard glycosylation, lacks functional enzyme -> no extra chain, anti-A and anti-B antibodies
type A: standard glycosylation, N-acetylgalactosamine, anti-B antibodies
type B: standard glycosylation, galactose, anti-A antibodies
type AB: both A and B antigens, no antibodies

Question 11

properties of erythropoietin (EPO)

Answer 11

produced by kidneys
response to hypoxia (HIF-1)
stimulates erythrocyte production

Question 12

properties of EPO receptor

Answer 12

binds EPO
expressed by proerythroblasts and normoblasts
uses Jak/STAT pathway
action: antiapoptotic, proliferation

Question 13

clinical relevance of recombinant EPO (rHuEPO)

Answer 13

chronic kidney disease: kidneys cannot produce enough EPO -> anemia
chemotherapy: RBCs depleted by treatment -> use to promote regeneration
blood doping: detectable by isoelectric point of different isoforms

Question 14

thrombocytes - properties

Answer 14

anucleate
membrane-bound cytoplasmic fragments
contain granules with clotting factors/activators, adhesion and vasoconstriction signals, hydrolytic enzymes and clot resorption signals

Question 15

describe process of thrombopoiesis

Answer 15

occurs in bone marrow

1) HSC
2) CMP - induced by GM-CSF and IL-3
3) MEP
4) Megakaryocyte-Committed Progenitor Cell (MKP)
5) Megakaryoblast - undergoes endomitosis (chromosomes replicate but cell does not divide), induced by TPO
6) Megakaryocyte - multi-lobed nucleus, basophilic granules, undergoes karyokinesis (division of nucleus) and cytokinesis (division of cytoplasm)

Question 16

properties of thrombopoietin (TPO)

Answer 16

produced primarily by liver (kidneys, bone marrow)
regulator of platelet production
prevents apoptosis, promotes maturation/proliferation
synergistic with platelet agonists -> promotes thrombosis

Question 17

properties of c-Mpl receptor

Answer 17

binds TPO

expressed on platelets, megakaryocytes and precursors

Question 18

clinical relevance of TPO

Answer 18

liver failure: no TPO -> no platelets -> thrombocytopenia

thrombocythemia: inherited activating mutation; abnormal clotting due to increased platelets
thrombocytosis: secondary increase of platelets

Question 19

describe process of granulopoiesis

Answer 19

occurs in bone marrow
maturation in connective tissue
1) CMP
2) Granulocyte/Monocyte Progenitor (GMP) - N, E, or B progenitors
3) Myeloblast - spherical nucleus w/ 3-5 nucleoli
4) Promyelocyte - all azurophilic granules produced here
5) Myelocyte - production of specific granules begins
6) Metamyelocyte - can no longer divide, specific granule production differentiates subtypes
7) Band Cell (N only) - nucleus elongates, horseshoe appearance
8) Mature Granulocyte - nuclear lobes appear
9) differentiation in connective tissue

Question 20

neutrophils - properties

Answer 20

induced by G-CSF, IL-3, and GM-CSF
3-5 lobed nucleus
no cytoplasmic staining
50-70% of circulating leukocytes
primary defenders

Question 21

eosinophils - properties

Answer 21

induced by IL-5, IL-3, and GM-CSF
bilobed nucleus
eosinophilic (red) staining (due to specific and azurophilic granules)
1-5% of circulating leukocytes
primarily react to parasites

Question 22

when is eosinophilia detected?

Answer 22

parasitic infxn (uncommon in developed countries)
allergic rxns
iatrogenic

Question 23

basophils - properties

Answer 23

induced by SCF, IL-3, and GM-CSF
lobed nucleus obscured by dense granules
intense basophilic (blue) staining (due to specific and azurophilic granules)
<1% of circulating leukocytes

Question 24

when is basophilia detected?

Answer 24

lymphoproliferative syndromes often produce basophilia

Question 25

monocytes - properties

Answer 25

largest of WBCs
nucleus w/ indentation site at center
small, dense, azurophilic granules
circulate for 3 days
differentiate in local tissues, can persist peripherally for years

Question 26

IL-3 - properties

Answer 26

produced by CD4+ T cells
general hematopoietic cytokine
promotes expansion of immature marrow progenitors into all types of mature hematopoietic cells

Question 27

GM-CSF - properties

Answer 27

granulocyte-macrophage colony stimulating factor
promotes maturation of bone marrow cells into dendritic cells and monocytes
produced at infection sites to mobilize neutrophils
used to recover from cancer chemo and bone marrow transplantation

Question 28

lymphocytes - properties

Answer 28

histologically distinguishable by size

small: dormant, inactivated; slightly indented nucleus, intense staining, thin pale blue rim; 90% of circulating lymphocytes
large: activated

Question 29

B cell - properties

Answer 29

produce antibodies (humoral immunity)
variable lifespan

Question 30

T cell - properties

Answer 30

cell-mediated immunity
undergo differentiation in thymus
long life span

Question 31

natural killer cell - properties

Answer 31

induce apoptosis in infected or “non-self” identified cells
larger than T and B cells
kidney-shaped nucleus
large cytoplasmic granules

Question 32

IL-7 - properties

Answer 32

produced by stomal cells of many tissues

stimulates expansion of immature B and T cells

Question 33

X-linked severe combined immunodeficiency (SCID)

Answer 33

mutated T cell-specific IL-7R

decreased T cells, normal or increased B cells