Red Blood Cells & Anemias

Andrew D. Leavitt, MDDepartments of Laboratory Medicine & Medicine

March 26, 2012

RBC: ~5 x 106/l; Generate ~ 8,000,000,000/hour

Outline – topics we will cover

Erythropoiesis

Pro-Erythroblast

BasophilicErythroblast

PolychromaticErythroblast

OrthochromaticErythroblast Reticulocyte RBC

CHROMATIN STRUCTURE

NUCLEAR SIZE & COLOR

5 stages in the marrow

Red Blood Cell (RBC)

Delivers O2 from your lungs to all your tissuesTakes CO2 from your tissues to your lungs

Also – binds NO (a vasodilator)

Their size: 8 [capillaries have ~3 M diameter]

Their life-span: 120 days

Mature RBCs have no nucleus

Too few RBCs = anemia

What tells your body to make RBCs?

EPO:Is not stored, but expressed in response to the kidney sensing oxygen in the blood

It -1. Increases # of E-committed progenitors2. Increase GATA1 and FOG expression3. Enhances anti-apoptotic gene expression4. Increases transferrin receptor expression

Hemoglobin

Tetramer of two heterodimers (&)

Hemoglobin (Hgb) in the RBC carries O2, which is poorly soluble in water, to tissues & CO2 from tissues to lungs.

~640,000,000 Hemoglobin molecules/RBC

Must coordinate: 1.heme and globin synthesis 2. (Chromosome 11; 141 aa) & (Chromnosome 16; 146) chains

Colors of a bruise are globin breakdown products

HemeIron in a Porphyrin ring

Glu to Val

Linus Pauling1949 – molecular diagnosis

2012 – no therapy

Hemoglobin oxygen dissociation curve

ArterialO2 tension

Mean VenousO2 tension

HbF

; CO2

Erythropoiesis: Hemoglobin Switching(ALWAYS: 2 alpha & 2 “beta-like” [3 ‘’ options])

Embryo Fetus Birth Adult6 mo.

Glo

bin

chain

synth

esi

s (%

)

0

50

HgF (75)

HgA (25)

HgA (96-98)

HgA2 (2-3)

HgF (< 1)

Hoffman et al. Hematology 2000

Alpha: Chromosome 16Beta-like: Chromosome 11

*

*

*mutations lead to hereditary spherocytosis

Schematic of red cell membrane depicting proteins crucial for normal membrane mechanical strength

Normal Values for Hematology Tests - UCSF

Thinking about anemia…a clinical perspective

Framework: RBC size (MCV) & is the marrow responding (reticulocyte count)

Etiology:Cell intrinsic:

1. Hgb – too little; abnormal type; unequal and synthesis2. Enzyme3. Membrane

Cell extrinsic:Immune mediatedPhysical destruction

Blood loss

Marrow does not producePrimary – leukemia, myelodysplasiaSecondary – vitamin deficiency

Reticulocyte Stain – detects the ribonucleoprotein in the young RBC

Reticulocytes

#1.1 Too little Hgb: Iron Deficiency Anemia

Small cells – microcytic (MCV < 80 fL)

Young women – OK

Older people – Worry about gastrointestinal blood loss

Iron deficiency anemia, peripheral blood (40x)normal peripheral blood (40x)

Lead poisoning can look like Fe deficiency – Lead blocks heme synthesis

Iron Deficiency Anemia

peripheral blood, 100X

HypochromicRBCs

Elliptocytes

Iron stian of bone marrow – none found

~ 500 million people worldwide

Daily absorption:Duodenum ~ 1 mg

Daily loss: urine, feces, skin, hair ~ 1 mg

Transferrin

Plasma (4 mg)

Circulating RBCs (1.7 – 2.4 gm)

Menstrual loss/hemorrhage

Macrophage(0.5 – 1.5 gm)

Ineffective erythropoiesis

Bone MarrowErythroblasts( ~ 150 mg)

The Iron Circuit – mostly a game of recycling

Weiss & Goodnough NEJM 2005

Iron Circuit in Disease

Infection/inflammation/malignancy

IL-6/LPS hepcidin (25aa protein)absorptionmacrophage Fe storageImpairs Erythropoiesis: Decrease EPO Directly suppresses marrow

Interferon –

TNF –

IL-1, IL-10

Storage iron(blue)

Iron deficienyc anemia - iron stain

Anemia of inflammation – iron stain

Iron stain of bone marrow aspirates

#1.2 Abnormal Hgb: Sickle cell disease

Multi-system disease

Cardiovascular/strokesKidneysSkinLungsImmune system

Treatment:

Supportive careTransfusionsDemethylating agentsStem cell transplants

#1.3 Abnormal / Globin ratio: Thalassemia

Small cells – microcytic (MCV < 80 fL)

Imbalance between and chains

Name based on which chain is deficient [ or thal]

Make lots of RBCs, just unstable and lyse, so increased retics

Alpha Thal:silent carrier trait or

Hgb H Hydrops fetalis

Beta Thal:MinorIntermediaMajor

Erythropoiesis: Hemoglobin Switching(ALWAYS: 2 alpha & 2 “beta-like” [3 ‘’ options])

Embryo Fetus Birth Adult6 mo.

Glo

bin

chain

synth

esi

s (%

)

0

50

HgF (75)

HgA (25)

HgA (96-98)

HgA2 (2-3)

HgF (< 1)

Hoffman et al. Hematology 2000

Alpha: Chromosome 16Beta-like: Chromosome 11

Beta-thalassemia major

Nucleated RBC

Target cells

Alpha thal traitNormal peripheral smear

Hemoglobin H, -- / -A

Target cells

Retics

Severe thalassemia

Beta-thalassemia major

Nucleated RBC

Target cells

Beta-thalassemia major (transfused)

NucleatedRBC

Normal RBCs(transfused)

Bite cells

#2 Enzyme: G-6-PD deficiency (Heinz body hemolytic anemia)

Arrows show Heinz bodies

Sulfa drugs, fava beans, antimalarials..…

Reduced glutathione (GSH)is critical for RBCs to counter

oxidative stress.

*

*

*mutations lead to hereditary spherocytosis

#3: Membrane: red cell membrane depicting proteins crucial for normal membrane mechanical strength

Hereditary spherocytosis (HS)

spherocytes

Reticulocytes

Thinking about anemia…a clinical perspective

Framework: RBC size (MCV) & is the marrow responding (reticulocyte count)

Etiology:Cell intrinsic:

1. Hgb – too little; abnormal type; unequal and synthesis2. Enzyme3. Membrane

Cell extrinsic:Immune mediatedPhysical destruction

Blood loss

Marrow does not producePrimary – leukemia, myelodysplasiaSecondary – vitamin deficiency

Autoimmune hemolytic anemia

spherocytes

Reticulocytes

Testing for anti-RBC antibodies: attached or in circulation

Hemolytic disease of the newborn

RBC destruction - extrinsic

Hemolytic uremic syndrome (HUS)

Retics

schistocytes(RBC fragments)

Thrombotic thrombocytopenic purpura (TTP)schistocytes

(RBC fragments)

Erythroid Hyperplasia, TTP, bone marrow aspirate (100x)

Megaloblastic anemia (MCV > 100)

B12 deficiencyFolate deficiency

Affects DNA synthesis

Megaloblastic anemia (MCV > 100)

Anemia yet hypercellular marrow – ineffective erythropoiesis

Narla & Ebert 2010

Ribosomopathies and hematopoietic disorders

Our findings indicate that the erythroid lineage has a low threshold for the induction of p53, providing a basis for the failure of erythro- poiesis in the 5q- syndrome, DBA, and perhaps other bone marrow failure syn- dromes.

Thanks for your attention!

Take home message……

Blood is good…everyone should have some!

Share it…become a blood donor if you can

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Millberry Union next to Subway sandwich shop

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