Cells taken from blood, marrow and spleen are injected into a lethally irradiated mouse. The spleen is harvested after 8-14 days, with appreciable colonies on spleen (although the most are in the bone marrow).

Chromosome markes demonstrate monoclonalism of colonies.

Stochastic= permissive; stem cells randomly differentiate or mitose, which is supported by environmental chemokines

Deterministic= directive; stem cell fate is determined by cytokines and ECM in micro-environment

Most discernible, CD34+ CD38-

Also, Thy1+, Lin-, CD45RA-

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Note, only CFU-E responds to EPO

• Increase of epo...
  • Anemia
    • Poor oxygenation of blood
    • Altitude sickness
    • Lung disease
    • Abnormal HgB
• Decrease of epo...
  • End stage renal disease

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Note: IL-3 and G-CSF are used both in early and late differentiation.

Mouse studies suggest that GM-CSF is not essential for hematopoesis, but could have affect on pulmonary macrophage production.

• 12-13 days to go from myeloblast to peripheral blood.
• 6-12 hour half-life in circulation
• Generally half are freely circulating and half are adhered to endothelium (marginal pool). Physical stress causes shift to circulating pool (transient leukocytosis)

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Megakaryocytes mature by increasing nuclear size by factors of 2 (eg 2n, 4n, 8n, 16n), and "blebbing" off platelets.

TPO is manufactured in the liver.

Macrocytes

Typically oval, too thick to display central pallor.

Spherocyte

Lack central pallor, with more intense color. Can be seen in autoimmune hemolytic anemia (RE cells take a chomp out the RBC cytoskeleton), hereditary cytoskeleton defect, or HbC

Elliptocyte

Can be due to iron deficiency or myelofibrosis

Teardrop RBC

Pointed tail, characteristic of myelofibrosis

1. Iron deficiency
2. Thalassemia (failure in hemoglobin production)
3. Anemia of chronic disease

1. Increased reticulocytosis
2. Liver disease
3. Agglutinin disease
4. Hypothyroidism

Indicates dehydrated RBC; >32-36 g/dL

1. Heriditary spherocytosis
2. Sickle cell anemia
3. Homozygous HbC

1. Iron defficiency
2. MCH = 27-33, RDW = 11.5-14.5%
3. Thalassemia (hemoglobin deficiency)

>20%

1. Combined vitamin deficiencies (B12/folate for macrocyte, iron for micro)
2. MDS
3. Micoangiopathic hemolysis (reticulocytes observed)

1. Traumatic hemolysis (intravascular hemolysis)
2. Absent haptoglobin, urobilinogen in urine, hemosiderinurea (present several weeks after trauma)
3. Can be due to turbulent flow (heart disease, stent), coagulation, or vigorous exercise.

Hereditary spherocytosis

Lack of ankryn leads to decreased structural RBC integrity unable to form biconcave shape. The porous membrane leads to ion leakage and consequent ATP depletion. This results in a sphere-like cell that is prone to RE destruction (hence, splenomegaly).

African-American male comes into clinic with signs of anemia. Histology shows cells with "bite-marks" taken out of them, while special staining for Heinz bodies show up positive. What is the most likely diagnosis and the mechanism of cell destruction?

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G6PD deficiency

An X-linked recessive trait seen in 10% of AA males. Failure in the HMP shunt prevents glutathione from returning to its reduced form. This makes the RBC more prone to oxidative stress and the formation of Heinz bodies. When navigating through meshwork of spleen or bone marrow, these bodies can get caught up and removed, leading to the appearance of "bite marks" typical of the disease.

Direct Coombs; autoimmune hemolysis.

Presence of antibodies initiates RE cell endocytosis. Cells that can escape complete endocytosis typically become spherocytes similar to those seen in hereditary spherocytosis.

Lymphoproliferative disease and SLE would also suggest warm autoimmune response.

1. Oval macrocytosis [image]
2. Variation in RBC size (anisocytosis) with RDW >20% possible
3. Hypersegmentation (some neutrophils with 6-10 lobes, or significant number of neutrophils with 4-6 segments)
4. Howell-Jolly bodies (nuclear fragments from lysed RBCs)

Pallor, scleral icterus (jaundice) from indirect bilirubin released from lysing cells, glossitis (smooth, red tongue)

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Only B12 deficiency will have neurological deficiencies (e.g wide gait, loss of proprioception, spasticity)

Intrinsic factor not produced (pernicious anemia / Addisonian). Antibodies typically directed against parietal cells (85% of cases, but not specific for PA) or IF itself (65% of cases, but 100% specific for PA)

Dietary problems are rare, since a person would have to avoid B12 for at least 3 years to deplete stores. Other possibilities include terminal ileum malaborption due to Crohn's, fish tapeworm or bacterial overgrowth.