Lecture 11 - White blood cells

Question 1

How do white blood cells deal with the flexible needs of the body?

Answer 1

Cooperation between cell types is needed, this allows for flexibility in doing their jobs

Question 2

White blood cells: the granulocytes and monocytes

Answer 2

Granulocytes:
Neutrophil
Eosinophil
Basophil

Monocytes:
B lymphocyte
T lymphocyte
Natural killer cells

Question 3

Killing large organisms: what examples and what white blood cells deal with them?

Answer 3

Large organisms - ie worms

Eosinophils and basophils

Question 4

Killing small organisms: what examples and what white blood cells deal with them?

Answer 4

Bacteria

Neutrophils and monocytes

Question 5

Killing viruses: what examples and what white blood cells deal with them?

Answer 5

Viruses entering host cells, needing the entire cell to be destroyed

T-lymphocytes and natural killer cells

Question 6

Killing toxins: what examples and what white blood cells deal with them?

Answer 6

Bacterial toxins/blood pathogens

Antibody-secreting B-lymphocytes

Question 7

Amoeba

Answer 7

Free-living microorganism moves freely:
* It recognises and ingests prey (non-self)
* It recognises but does not ingest other amoeba as non-prey (self)

Question 8

What does the innate immune system use to detect ‘self’ and non-‘self’

Answer 8

Proteins and any other key markers for ‘self’, DAMPs, and PAMPs

Question 9

What increases white cell recruitment to where it is needed?

Answer 9

Cytokines stimulate the release of white cells from marrow

Chemokines, activated by DAMPs and PAMPs, also cause white blood cells to gather in inflamed tissue

• G-CSF stimulates neutrophils
• CXCL8 stimulate neutrophils into inflamed tissue
• IL-8 stimulates neutrophils into inflamed tissue

Question 10

What happens after the infection is defeated?

Answer 10

Fewer PAMPs and DAMPs released:

• Reduced white cell production
• Reduced entry into infected areas
• Reduced activation

Question 11

Neutrophils: how their function aids the body?

Answer 11

Due to their small size bacteria can be engulfed by neutrophils and digested, this means the bacteria are destroyed within neutrophils allowing the killing to occur without damage to tissues.

Question 12

Neutrophils: what do they do and how do they do it?

Answer 12

Becomes “primed” to kill organisms:
* Increasing energy availability (glycogen stores)
* Increasing granulation - making more enzymes * Enhancing the ability to move and adhere to pathogens

• Adheres to bacteria using adhesion receptors then engulfs them into the cell interior within a phagosome
• Granules fuse with phagosome to destroy bacteria:
• Microbiocidal - myeloperoxidase, lysozyme,
• Acid hydrolases
• Iron binding - Lactoferrin
• Extracellular traps:
• DNA net

Question 13

Neutrophils: what are they, what do they do, how long do they last for, and what is their standard state?

Answer 13

Highly motile cell, which can enter tissues at sites of inflammation

Survives 12-24 hours in blood
Further 24-48 hours in tissues

Most neutrophils simply live out their lives and then die without needing to perform infection. The key therefore is to do nothing unless stimulated this avoids damaging the body

Question 14

How do neutrophils avoid damaging ‘self’ cells?

Answer 14

Phagocytoses cells - destroyed internally

Enzyme contents are relatively safe if released: as they depend on low pH or oxidising power which are only found within the cell

Following cell killing neutrophils die by apoptosis avoiding tissue damage

Question 15

Monocytes: what is it and what does it do?

Answer 15

Phagocytic like the neutrophil but acting mainly in tissues

• Has a “walling” function to trap infection and prevent it from spreading
• Begins tissue repair by removing dead tissues and beginning the process of repair
• Related to adaptive systems where it may have an antigen-presenting role
• Spend 17 hours in blood before entering tissues where they become “tissue macrophages”

Question 16

The power of macrophage walls

Answer 16

Difficult infections are walled in to prevent spread where the infection can then be reduced over a long period or sometimes simply remain localised and prevented from causing harm (dormant)

Such infections may reactivate in future times if the immune system is supressed.

Question 17

Eosinophils and basophils

Answer 17

These cell types have overlapping functions and general characteristics so are considered together - Eosinophils have granules not overlapping the nucleus whereas basophils do (one key difference)

The granules are released into the space around pathogens to act – since granules are the main effective element the cells are densely granular.

Question 18

Granule contents of Eosinophils and basophils

Answer 18

Histamine: dilates blood vessels allowing for more blood cells to arrive, and causes swelling that traps invading organisms.

Contain multiple active proteins: Nucleases that break down DNA/RNA, Lipases that break down fat, and Major basic proteins that attack the organism’s surface

Potentially cause tissue toxicity as all these proteins may also damage tissues

Question 19

Granule contents’ role in inflammation

Answer 19

• Histamine – dilate blood vessels
• Serotonin – dilates blood vessels
• Heparin – prevents clotting
• Enzymes (elastase) break down tissue matrix
• IL4 – stimulates immune reactions, especially IgE

Question 20

What conditions arise when neutrophils have their functions completed incorrectly?

Answer 20

Benign diseases - chronic infection, rheumatoid arthritis

Question 21

What conditions arise when eosinophils have their functions completed incorrectly?

Answer 21

Heart valve damage

Question 22

What conditions arise when basophils have their functions completed incorrectly?

Answer 22

Harmful granule release:
* Allergic reactions
* Asthma

Question 23

Cytokine storms

Answer 23

In some instances an immune response to infection becomes uncontrolled with cytokine and chemokine production causing excessive activation of inflammatory cells, causing the destruction of normal tissues that further increases cytokine release a ‘cytokine storm’. This provokes increasing uncontrolled inflammation.