Session 3 ILOs - Haemopoesis and FBC (and films)

Question 1

Understand and explain the basics of haemopoiesis

Answer 1

Haemopoiesis is the production of blood cells, that occurs in the bone marrow (mainly in the axial skeleton)

There are 5 lineage pathways, arising from the multipoint haemopoeitic stem cell. Differentiation is determined by hormones, transcription factors and interactions with non-haemopoetic cell types e.g. endothelial cells

Question 2

Describe the functions of the main blood cell types:

• RBC
• Neutrophils
• Monocytes
• Eosinophils
• Basophils
• Lymphocytes

Answer 2

RBC:
- To deliver oxygen to tissues by haemoglobin (plus generate energy to do this)

Neutrophils:

• First responder phagocyte (most common WBC)
• Essential part of the innate immune system and carries out phagocytosis

Monocytes:

• Circulate in blood for 1-3 days before migrating into tissues and becoming macrophages
• Phagocytose microorganisms but also has antigen presenting role
• Important in defence against chronic bacterial infections

Eosinophils:

• Defence against multicellular parasites
• Mediator of allergic responses (inappropriate responses e.g. asthma)
• Phagocytosis of antibody-antigen complexes
• Has granules containing cytotoxic proteins

Basophils:

• Active in allergic reactions and inflammatory conditions
• Has granules containing histamine, heparin, hyaluronic acid and serotonin

Lymphocytes:
- Originate in bone marrow
- 2 main types
1. B cells - responsible for humeral immunity and are antibody cells
2. T cells - responsible for cellular immunity (CD4+ helper cells, CD8+cells)
(plus Natural killer cells responsible for cell mediated cytotoxicity)

Question 3

Describe the roles of the spleen

Answer 3

Roles of the spleen: main role overall is to filter the blood

1. Sequestration and phagocytosis - of old/abnormal RBCs
2. Blood pooling
3. Extramedullary haemopoesis - can make cells if bone marrow is under stress
4. Immunological function - keeps 25% of T cells and 15% of B cells

Question 4

Understand the causes and clinical significance of splenomegaly

Answer 4

Causes:

• Portal hypertension in liver disease
• Over work of red or white pulp
• Carrying out extramedullary haemopoesis
• Infiltration of cells e.g. blood cancer cells
• Infiltration by other material e.g. sarcoidosis

Clinical significant:

• An enlarged spleen is no longer protected by the rib cage so it is at risk of rupture
• Therefore, avoid contact sports and vigorous activity

Question 5

Understand the causes and clinical significance of hyposplenism

Answer 5

Hyposplenism - lack of functioning spleen (either not working or has been removed)

Causes:

• Splenectomy e.g. from trauma
• Sickle cell disease
• GI diseases
• Autoimmune disorders

Clinical significance:

• Risk of sepsis from encapsulated bacteria
• Patients need to be immunised and given long life antibiotic prophylaxis

Question 6

Explain the concepts of a normal range

Answer 6

Normal range is estimated from volunteers and includes 95% of the healthy population (can vary from region to region).

Remember, 2.5% normal values sit below the range and 2.5% normal values sit above the range.

Normal range can change with: age, sex, ethnicity or co-morbidities

Question 7

Explain the significance of the reticulocyte count

Answer 7

Reticulocyte count is a measurement of number of new RBCs (young)

Increased reticulocyte count:

• Indicates that there is recent loss of RBCs and the body is compensating by producing new RBCs (reticulocytes)
  e. g. haemolytic anaemia, response to EPO etc.

Decreased reticulocyte count:

• Either due to haematinic deficiency (doesn’t have the components to make RBCs)
• Bone marrow deficiency

Question 8

What is hyperlipoproteinaemia?

Answer 8

Any condition in which, after a 12 hour fast, the plasma cholesterol and/or plasma triglyceride is raised

Question 9

What classes of lipoprotein are present in the serum from a fasting blood sample taken from a normal individual and what are their functions?

Answer 9

1. VLDL (Transport of triacylglycerol synthesised in liver to tissues)
2. LDL (Transport of cholesterol from liver to tissues
3. HDL (transport of excess cholesterol from cells to liver for disposal)

(IDL would also be acceptable but NOT chylomicrons as this is a fasting sample)