L5 Haemopoiesis

Question 1

Haemopoiesis

Answer 1

− A process that generates blood cells of all linages through via ligand-receptor dependent differentiation
expansion of specific cell types under pathological conditions.
highly regulated balance between self-renewal, differentiation and cell death

Question 2

HSC niche – cellular, molecular & biophysical

Answer 2

• HSC function is tightly controlled to maintain haemopoietic homeostasis or ‘mobilisation’.
• This regulation relies on specialised cells and factors that constitute the hematopoietic ‘niche’, or microenvironment

Question 3

Lymphocytes

Answer 3

• WBC (B- & T-cells)
• 20-45%
• Most are enmeshed in lymphoid connective tissue, e.g. lymph nodes, tonsils, spleen

Question 4

T-cells

Answer 4

T-cells attack foreign cells directly

− Killer cells (“cytotoxic”), or CD8+ is a main type

Question 5

B cells

Answer 5

− Differentiate into plasma cells
− Plasma cells secrete antibodies
− Antibodies flag cells for destruction by macrophages

Question 6

Monocytes

Answer 6

• 4-8% of WBCs
• In connective tissue they transform into macrophages (phagocytic cells with pseudopods)
Microglial cells present in the brain

Question 7

Neutrophils

Answer 7

•	60% of all WBCs 
•	Nuclei of 2-6 lobes 
Granules have enzymes 
Can damage tissue if severe or prolonged 
−	Pus

Question 8

Mast cells

Answer 8

− Allergic response

− Rapidly degranulate upon crosslinking of specific IgE by corresponding allergens and release preformed histamine

Question 9

Basophils

Answer 9

• Rarest WBC 

• Bilobed nucleus 

• Dark purple granules 

• Later stages of reaction to allergies and parasitic infections

Question 10

Eosinphils

Answer 10

• Late allergic response
• 1-4 % of leukocytes
• Bilobed
• Granules have digestive enzymes
• Role in ending allergic reactions and in fighting parasitic infections

Question 11

Platelets

thrombocytes

Answer 11

• Not cells
• Small fragments of / from megakaryocytes
• Important in forming clots in damaged vessels