Lecture 11 - White blood cells Flashcards
How do white blood cells deal with the flexible needs of the body?
Cooperation between cell types is needed, this allows for flexibility in doing their jobs
White blood cells: the granulocytes and monocytes
Granulocytes:
Neutrophil
Eosinophil
Basophil
Monocytes:
B lymphocyte
T lymphocyte
Natural killer cells
Killing large organisms: what examples and what white blood cells deal with them?
Large organisms - ie worms
Eosinophils and basophils
Killing small organisms: what examples and what white blood cells deal with them?
Bacteria
Neutrophils and monocytes
Killing viruses: what examples and what white blood cells deal with them?
Viruses entering host cells, needing the entire cell to be destroyed
T-lymphocytes and natural killer cells
Killing toxins: what examples and what white blood cells deal with them?
Bacterial toxins/blood pathogens
Antibody-secreting B-lymphocytes
Amoeba
Free-living microorganism moves freely:
* It recognises and ingests prey (non-self)
* It recognises but does not ingest other amoeba as non-prey (self)
What does the innate immune system use to detect ‘self’ and non-‘self’
Proteins and any other key markers for ‘self’, DAMPs, and PAMPs
What increases white cell recruitment to where it is needed?
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
What happens after the infection is defeated?
Fewer PAMPs and DAMPs released:
- Reduced white cell production
- Reduced entry into infected areas
- Reduced activation
Neutrophils: how their function aids the body?
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.
Neutrophils: what do they do and how do they do it?
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
Neutrophils: what are they, what do they do, how long do they last for, and what is their standard state?
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
How do neutrophils avoid damaging ‘self’ cells?
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
Monocytes: what is it and what does it do?
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”
The power of macrophage walls
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.
Eosinophils and basophils
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.
Granule contents of Eosinophils and basophils
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
Granule contents’ role in inflammation
- Histamine – dilate blood vessels
- Serotonin – dilates blood vessels
- Heparin – prevents clotting
- Enzymes (elastase) break down tissue matrix
- IL4 – stimulates immune reactions, especially IgE
What conditions arise when neutrophils have their functions completed incorrectly?
Benign diseases - chronic infection, rheumatoid arthritis
What conditions arise when eosinophils have their functions completed incorrectly?
Heart valve damage
What conditions arise when basophils have their functions completed incorrectly?
Harmful granule release:
* Allergic reactions
* Asthma
Cytokine storms
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.
