2 - White Blood Cell Structure and Function

Question 1

What two cell types do pluripotent stem cells in the bone marrow differentiate into?

Answer 1

Lymphoid stem cells - specific immune cells

Myeloid stem cells - innate immune cells

Question 2

What cytokines are involved in the differentiation of pluripotent stem cells into myeloid stem cells then into monocytes and granulocytes?

Answer 2

Pluripotent stem cell -> myeloid stem cell (IL3)

Myeloid stem cell -> monocyte (GM-CSF)

Myeloid stem cell -> granulocyte (G-CSF + IL5)

Question 3

What are the two types of granules present in neutrophils and their functions?

Answer 3

Primary granules - hydrochloric acid + myeloperoxidase (enzyme that catalyses formation of HOCl from HCL and H2O2) and neutrophil elastase

Secondary granules - lysozyme + collagenase + lactoferrin (destroy bacterial cell walls)

Question 4

What are two examples of common causes of neutrophilia one example of a rare cause?

Answer 4

Common - bacterial infection, corticosteroid therapy

Rare - myeloid leukaemia

Question 5

What is the lower normal limit of neutrophils in the blood and at what level does neutrophil count become dangerously low?

Answer 5

Lower normal limit - 1.8x10^9 /L

Dangerously low - <0.5x10^9 / L

Question 6

What is an example of a mild and a severe cause of neutropenia?

Answer 6

Mild - idiopathic neutropenia (young women esp Afro-caribbean)

Severe - chemotherapy

Question 7

What is an example of a common and a rare cause of neutrophil dysfunction?

Answer 7

Common - steroid therapy

Rare - lazy leukocyte syndrome

Question 8

What are the three eosinophil granules and their functions?

Answer 8

Major basic protein (MBP) - very alkaline, very toxic to worms

Eosinophil cationic protein (ECP) + Eosinophil-derived neurotoxin - RNAse enzymes, potent antivirals + toxic to worms and bacteria

Question 9

What are three causes of eosinophilia

Answer 9

• Worm and other parasite infections
• IgE-mediated type 1 hypersensitivity reactions
• Cancer

Question 10

What is the link between basophils and mast cells?

Answer 10

Basophils are mast cells that circulate in blood

Question 11

What are contained in basophil granules?

Answer 11

• Heparin (anticoagulant)
• Histamine (proinflammatory molecule)

Question 12

What are two causes of monocytosis?

Answer 12

• Chronic infection such as TB or typhoid
• Some types of myeloid leukaemia

Question 13

What are two causes of lymphocytosis?

Answer 13

• Acute viral illness
• Cigarette smoking