Blood Components & Cell Lineage

Question 1

Blood vs plasma vs serum

Answer 1

• Blood - cellular components + plasma
• Plasma - liquid component, including coagulation factors
• Serum - plasma (liquid component) minus coagulation factors

Question 2

What is the process that produces blood cells

Answer 2

Haematopoiesis

Question 3

Where does haematopoiesis occur and how does this change with age

Answer 3

• Embryo (0-3 months) - yolk sac then liver
• Embryo (3-7 months) - marrow + spleen
• At birth - mainly marrow (+ liver & spleen when required)
• With growth - only active marrow in axial skeleton, pelvis & proximal long bones

Question 4

What is the first cell in the blood cell lineage

Answer 4

Haematopoietic stem cells

Question 5

What processes do stem cells carry out? What state are most stem cells found in?

Answer 5

• Proliferation
• Differentiation (into specialised cells)
• Self renewal
• Most stem cells sit in a quiescent state (reversible non-dividing state)

Question 6

Describe the haematopoietic tree/ lineage

Answer 6

Haematopoietic stem cells (HSCs) =>
Multi-potent progenitors (MPPs) =>
Common myeloid progenitor (CMP) & Common Lymphoid progenitor (CLP)

————————————————————————————

Common myeloid progenitor (CMP) =>
Megakaryocyte-erythroid progenitor (MEP) & Granulocyte-monocyte progenitor (GMP)

MEPs => RBCs & platelets
GMPs => Granulocytes & macrophages

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Common Lymphoid progenitor (CLP) =>
Dendritic cells, T-cells, NK-cells, B-cells

Question 7

What are granulocytes? What are the three main types?

Answer 7

Granulocytes - WBCs that contain granules that are easily visible on stained blood film

Eosinophils - Take up eosin stain (red & acidic)
Basophils - Take up basic stains (densely blue)
Neutrophils - ‘Neutral’ mix of two colours

Question 8

Describe the structure of neutrophils

Answer 8

• Segmented, ‘polymorphic’ nucleus
• Neutral staining fine granules

Question 9

What is the main function of neutrophils? When may they increase in numbers?

Answer 9

• Phagocytosis & granule release (break down tissue & attract cells)
• Increase with bacterial infections, trauma, infarction etc

Question 10

Describe the structure of eosinophils

Answer 10

• Usually Bilobed
• Acidic (orange/ red) granules
• ‘tomatoes with sunglasses’

Question 11

When might eosinophil count be high?

Answer 11

• Parasitic infections, allergic reactions & conditions e.g. asthma

Question 12

Describe the structure of basophils

Answer 12

• Large, deep blue/purple granules
• Granules often obscure the nucleus

Question 13

Name some examples of molecules that are contained within basophil granules

Answer 13

histamine & heparin

Question 14

Describe the function of basophils

Answer 14

Function similar to mast cells, help mediate histamine release in IgE hypersensitivity reactions

Question 15

Describe the structure of monocytes/macrophages

Answer 15

• Large single nucleus
• Faint granules
• Light blue cytoplasm, often with vacuoles

Question 16

What is the difference between a monocyte & macrophages?

Answer 16

Monocytes - circulate blood for ~week
Macrophages - specialised monocytes that are active in tissues.

Question 17

Macrophage function

Answer 17

Macrophages are phagocytes and they are important in
- clearing debris,
- removing infective organisms
- presenting antigens to immune cells
- releasing signals to attract other cells

Question 18

Describe the structure of a mature vs activated lymphocyte

Answer 18

Mature lymphocyte - small, condensed nucleus, little cytoplasm
Activated lymphocyte - large cells, less condensed nucleus, big blue cytoplasm

Question 19

What feature can be used to help differentiate between a macrophage & activated lymphocyte

Answer 19

Activated lymphocytes often extend up to neighbouring RBCs on blood films

Question 20

What test can be used to differentiate between types of
A) haematopoietic stem cells
B) blood cell progeny (RBCs, neutrophils etc)

Answer 20

A) HSCs - immunophenotyping
B) Progeny - morphology on blood films

Question 21

Briefly describe tests used in haematological studies

Answer 21

FBC & blood films (to look at peripheral blood components)
Marrow biopsy (to look at bone marrow)
Special tests such as genetic testing & immunophenotyping
Spleen, liver & lymph node examination (blood production)

Question 22

Where is a bone marrow biopsy usually taken from

Answer 22

Posterior iliac crest

Question 23

Bone marrow aspirate vs bone marrow trephine/ column biopsy; What is the use of each?

Answer 23

Cellular aspirate - Can study cellular detail at higher magnitude
Trephine/ column biopsy - ‘Architectural map’ of cells in situ