White Blood Cells

Question 1

Outline the functions of the neutrophil?

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Answer 1

Neutrophils are white blood cells which hunt and kill bacteria

Bacteria release a chemo-attractant which is sensed by the neutrophil. The neutrophil becomes polarised and begins to chase the bacteria. The bacteria, bounced around by thermal energy, moves around seeming to avoid the neutrophil. Eventually the neutrophil catches up with the bacteria and engulfs it by phagocytosis

• Commonest WBC in blood (50-70% of total)
• Short lifespan of 8-10 hours
• Chemotaxis - neutrophils migrate in response (e.g- to bacterial wall antigens)
• Doesn’t recognise specific antigens
• Bacteria is ingested and killed by enzymes in granules
• Rise as acute response to bacterial infection, inflammation, malignancy

Question 2

Outline the functions of the eosinophil?

Answer 2

Eosinophils respond to Helminth infection

• Make up 1-6% of total blood WBC
• “Eosin” stains the granules orange/pink
• Lifespan in blood 4-5 hours, longer in tissues. Growth promoted by Interleukin-5
• Granules contain Major Basic Protein and reactive O2 species
• Chemokines attract them to specific tissues
• Marked rise in numbers in blood from 0.4 to 2-6 X 10 9/l
• Commonly seen in atopy eg eczema, asthma and hayfever
• Also in Hodgkin’s disease, Chronic myeloid leukaemia and other malignancy, adverse drug reaction
• Blood levels often correlate with clinical activity

Question 3

Outline the functions of the basophil?

Answer 3

• Make up <1% of total blood WBC
• Dark “basophilic” granules contain histamine, leukotrienes, proteases and heparin
• Also have a role in phagocytosis
• Cell surface receptor for IgE- binding produces degranulation following chemotaxis
• Role in hypersensitivity (allergic) reaction

Question 4

Outline the functions of the lymphocyte?

Answer 4

• Make up 20-40% of blood WBC
• Divide into T (thymus) and B (bone marrow or bursa)
Lymphocytes
• Differentiate early from other marrow derived cells
• Much longer life span in blood/marrow/lymph node
• T and B cell malignancies with circulating cells=
leukaemia

Question 5

Outline the functions of the monocyte?

Answer 5

• Make up 5-10% of circulating blood cells
• Granules containing hydrolases and myeloperoxidase
• Circulate for 8-12 hours but much longer in tissues
• Ingest material and present peptides to T cells- ie antigen presenting cells
• Role to kill mycobacteria and fungi and intracellular organisms eg listeria

Question 6

Define the term “chemotaxis”?

Answer 6

Bacteria release a chemo-attractant which is sensed by the neutrophil. The neutrophil becomes polarised and begins to chase the bacteria. The bacteria, bounced around by thermal energy, moves around seeming to avoid the neutrophil. Eventually the neutrophil catches up with the bacteria and engulfs it by phagocytosis

Question 7

Explain the importance of the differential count in clinical practice?

Answer 7

KEEPS

Question 8

Describe the events which occur in an allergic reaction?

Answer 8

KEEPS

Question 9

Describe what cells and molecules are involved in the humoral and cell-mediated responses?

Answer 9

KEEPS

Question 10

Give the 5 stages of phagocytosis?

Answer 10

Phagocytosis;
•	Leukocyte
•	Rolling
•	Arrest
•	Migration
•	Transmigration