Blood Cell Structure & Function Flashcards
What do you stain a blood smear with for viewing under a microscope?
Wright-Giemsa stain
Hb is going to pick up what stain under the microscope?
eosin. Due to its hydrophobic, basic nature
Numbers of this WBC type are found increased in the context of allergic reactions and infection with parasites:
Eosinophils
Mature cells of this WBC type are bi-lobed and have basic granules that pick up eosinophilic stain.
Eosinophils
Basophils pick up what stain with their acidic granules?
Methylene Blue
Eosin is an acidic or basic stain?
acidic. it stains basic molecules (eosinophilic granules)
Methylene blue is an acidic or basic stain?
basic. it stains acidic molecules (basophilic granules)
Eosinophils usually make up what percent of WBCs in a count?
< 5%
Basophils usually make up what percent of WBCs in a count?
< 1%
What would trigger basophils to degranulate?
presence of allergen
Describe the presence of cytoplasmic granules in monocytes and lymphocytes.
No granules
Monocytes make up between ____ - _____% of WBCs found in the blood.
3-8%
Monocytes give rise to this WBC found in tissue during infection or trauma.
Macrophages
Is monocytosis (lots of monocytes) specific for any particular pathology?
No
Lymphocytes make up ___-___% of blood WBCs.
20-30%
List the lymphocytes in order of predominance in the blood.
T cells, B cells, NK cells
Describe the life span of lymphocytes.
Days to years
Describe the morphology of a reactive lymphocyte.
“reactive” forms (which increase in number in viral syndromes) have more cytoplasm, sometimes prominent nucleoli
List the two “large, granular” lymphocytes.
Cytotoxic T cells and NK cells
Describe the morphology of large, granular lymphocytes.
NK and Cytotoxic T-cells sometimes show small numbers of basophilic cytoplasmic granules (“large granular lymphocytes”)
What cell is being described?
“Neutral” cells (Neutrophils)
with cytoplasmic granules that stain light pink, binding little of either eosin or methylene blue. “segmented” nuclei.
Neutrophils
Describe the lifespan of neutrophils.
Short. < 1 day
Describe the “weapons” of neutrophils in response to infection.
Phagocytosis
Degranulation
Formation of extracellular traps (NETS)
Describe the action of neutrophils in response to an infection.
Migrate in response to chemokines
Recognize and swarm the enemy
Degrade and immobilize the enemy
Minimize collateral damage
What are the cytokines that attract neutrophils?
IL-8. binds IL-8 receptor (CXCR-2) on neutrophils
What molecules on the neutrophil cell surface are responsible for “grabbing” and “holding” the infecting organism for destruction?
Integrins: CD11a/CD18 complex
What recognition receptors are present on the neutrophil cell surface for grabbing and holding infecting organisms?
Toll-like receptors
Complement receptors
Fc receptors
Neutrophils secrete these chemokines:
CXCL2
IL-8
TNF
Describe the neutrophil process for immobilizing and degrading invading organisms.
Phagocytose it (via the same receptors that recognized it) Chew up its polysaccharide cell wall with lysozyme Chew up its proteins with various proteases Kill it with bleach (hypochlorite)
Describe the neutrophil process that minimizes collateral damage.
Apoptosis
Release of chromatin-derived NETs
An immature neutrophil with a horseshoe shaped nuclei is called a ______ form, and is found normally in this percentage in smears.
band; < 5%
A form of neutrophil a step less mature than a band cell is termed a _________ , and has bean shaped nuclei.
metamyelocyte
A form of neutrophil a step less mature than a metamyelocyte is termed a __________ , and has a rounded nuclei.
myelocyte
The term, “left shift” refers to what, in the context of a neutrophil differential.
abnormal presence of immature neutrophils
Describe the granulation of a neutrophil present at a site of infection.
increased cytoplasmic granules (“toxic granulation”)
Describe the nuclei of platelets.
No nuclei
What happens to the platelet count in iron deficient pts?
It increases
Describe the life span of platelets.
9-10 days
Describe the function of platelets.
1) Primary hemostatic plug (adherence/activation/aggregation)
2) Stimulate coagulation cascade (fibrin formation/clot retraction)
3) Stimulate wound healing (fibroblast growth/migration)
4) Immune function (including antigen presentation and pathogen inactivation)
List the requirements of platelets that allow them to do their jobs well.
Must be present in large numbers Need to recognize damaged blood vessels Need to swarm onto the damage, fast Patch the damage Rebuild the vessel wall
Describe the quantity requirements of platelets to prevent spontaneous bleeds and stop small (non-spontaneous) bleeds.
You need about 10,000 per ul to not bleed spontaneously
You need about 50,000 per ul to stop most small bleeds
You store more in the spleen – they’re released when you get scared
Describe how platelets recognize damaged blood vessel walls and bind to factors, starting the repair process.
Bind subendothelial collagen via a surface protein called Gp1b
Functional augmentation scheme:
cable-like adaptor (vWF) sticks to the exposed collagen, changes shape slightly, flaps in the breeze
Platelets bind the adaptor (vWF)
Describe how deficiencies or defects in vWF can adversely affect bleeding and clotting.
If the adaptor (vWF) is in short supply, patients bleed a lot
If the adaptor is too short, patients bleed a lot
If the adaptor is too long, they clot excessively
Describe the process by which platelets swarm onto the damage of a blood vessel and begin repair by cross-linking.
Binding collagen or vWF causes platelet activation
Activated platelets bind vWF and fibrinogen more avidly
Fibrinogen is the precursor to fibrin. You have lots of it in your plasma.
That results in aggregation (mostly via crosslinking of platelets)
Activation/aggregation is autocatalytic; activated platelets secrete mediators that augment activation/aggregation
Describe how platelets patch and stabilize repair of damaged blood vessels.
Activation/aggregation also promotes activation of the coagulation cascade
A series of plasma proteases that, when activated, deposits a fibrous mesh, made up mostly of fibrin
AND
If the coagulation cascade gets activated first, it causes platelet activation
The final product is a strong, stable, fibrin-based clot
Describe the contribution of platelets to rebuilding the blood vessel wall.
Activated platelets secrete growth factors that stimulate fibroblasts and smooth muscle cells
What is the name of the cable that maintains the shape of a RBC and what are the proteins that make up the anchor points in the RBC plasma membrane?
Spectrin (alpha chain & beta chain); ankyrin, palladin, glycophorin
What happens to RBC flexibility if the Hb within RBCs precipitates?
Lose flexibility, jam up capillaries. Cells rupture.
How do RBCs maintain their osmotic gradient?
Pump Na out of the cell via Na/K ATPase pumps
Why must RBCs be anti-oxidant in nature?
O2 is a powerful oxidant (via generation of H2O2)
Oxidized–SH groups on hemoglobin become crosslinks (R1-SS-R2)
Result: Hgb denaturation and/or precipitation
Oxidized iron (Fe+++) can’t carry O2
Result: Hemoglobin containing Fe+++ (Methemoglobin)
Result: patient is hypoxic even though the top two causes of same (anemia, lung disease) might not be present
Describe the process by which Glutathione neutralizes the toxic effects of H2O2
Glutathione (GSH) eliminates peroxide before it can damage the machinery
Requires NADPH
Cytochrome b5 reductase reduces Methemoglobin back to normal hemoglobin
Requires NADH
Describe the design features that allow RBCs to make energy for themselves if they do not have mitochondria.
Design features:
Chuck the mitochondria
Use glycolysis to make ATP and NADH
Use the pentose shunt to make NADPH
First potential failure point in the pathway:
Glucose 6 phosphate dehydrogenase
Describe the process by which Glutathione neutralizes the toxic effects of H2O2
Glutathione (GSH) eliminates peroxide before it can damage the machinery
Requires NADPH
Cytochrome b5 reductase reduces Methemoglobin back to normal hemoglobin
Requires NADH
Describe the design features that allow RBCs to make energy for themselves if they do not have mitochondria.
Design features:
Chuck the mitochondria
Use glycolysis to make ATP and NADH
Use the pentose shunt to make NADPH
First potential failure point in the pathway:
Glucose 6 phosphate dehydrogenase
Describe a RBCs ability to tune down complement fixation.
Why it’s needed:
The alternative complement fixation pathway is active at a low rate all the time.
Normal blood cells have to slow it down to survive
How it works:
A normal cell surface protein slows down complement fixation
It’s called Decay accelerating factor (DAF, CD55)
First potential failure point in the system
What is poikilocytosis?
Poikilocytes are abnormally shaped red blood cells
How does residual mRNA present microscopically in RBCs?
Polychromasia (seen as elevated reticulocyte #, usually with accelerated production of RBCs)
-is a disorder where there is an abnormally high number of red blood cells found in the bloodstream as a result of being prematurely released from the bone marrow during blood formation.
What is poikilocytosis?
Poikilocytes are abnormally shaped red blood cells
How does residual mRNA present microscopically in RBCs?
Polychromasia (usually seen with accelerated production)
Why would Hb precipitate in RBCs?
Can be due to a genetic defect in Hb structure (hemoglobinopathy)
Can be due to oxidized Hb (forms small clumps, “Heinz bodies”)
What happens when Hb precipitates in a RBC?
Can alter the shape of the red cell (sickle shape, for example)
How can tissue-based phagocytes perform damage repair to oxidized Hb in RBCs?
remove chunks of the cell, resulting in “bite” cells (RBCs that look like a cookie with a bite taken out of it)
What are schistocytes?
RBC fragments. Can be due to mechanical lysis or “microangiopathic” processes. Resulting cells look as though they’ve been sliced in half.
What are the methods for quantifying blood cells?
manual count
Spectrophotometry
Conductivity (Coulter method)
Flow cytometry
How do we quantify Hb?
Spectrophotometry.
Lyse cells, add cyanide.
Color changes to varying degrees of blue. Quantify color change (% absorption). This gives you Hb concentration.
How do we quantify RBCs?
spin down the whole blood sample. RBC % of whole blood volume (RBCs, WBCs, plasma) is called hematocrit.
Under what pathological circumstances may you find giant platelets in a peripheral blood smear?
bone marrow pathology. Basically, stuff is getting kicked out of the bone marrow and into the circulation.
What are reticulocytes?
Circulating immature RBCs. They usually only circulate for a day before maturing and compose ~1% of the RBCs in the circulation.
How do you find hematocrit from Hb value?
multiply Hb by 3.
eg: Hb 15 = Hct 45
Finding Hb from Hct works in reverse. Divide by 3.
What is a faster and more accurate way to quantify RBCs than manually?
Conductivity (Coulter chamber)
- peak # = cell #
- peak height = cell volume
Describe the automated leukocyte differential.
Uses conduction (Coulter chamber). Alternating current as opposed to direct current with RBC quantifying. Peak height = cell complexity = lobulated nuclei & granules
If the RBC is producing an insufficient amount of ATP via glycolysis, what will happen to the RBC and why?
Cell will burst (lyse) from swelling with water because can’t work Na/K ATPase pumps to move Na out of the cell and reduce intracellular osmotic pressure
List a few quantitative limitations of automated cell analyzers.
Bands and other immature granulocytes are counted as neutrophils by most analyzers.
Blasts may be counted as lymphocytes or monocytes.
Red cell fragments may not be detected, will usually be counted as platelets.
Platelet clumps are not always detected by the analyzer and can result in an artifactual thrombocytopenia.
