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What are the 3 stages of an inflammatory response?

1.Mast cells and macrophages release cytokines.
2.these cytokines dilate the nearby blood vessels, increase the vascular permeability of the tissue and attract white blood cells.
3. phagocytosis occurs.


What is pus made up of?

Pus is made up of dead bacteria leukocytes, killed by leukocidins produced by the bacteria as well as old age.


What are acute phase reactants?

Substances produced by the liver in response to inflammatory cytokines like IL-1, examples of this are C reactive protein which binds to bacteria and activates the complement system and haptoglobin, which inhibits microbial iron uptake.


What are natural killer cells?

Large granular (granule releasing) cells which resemble lymphocytes. They help combat viral infections and cancer by the use of toxic molecules which directly kill target cells (virus infected or cancer) and also release cytokines which help other cells kill their targets.


What are toll like receptors?

Toll like receptors are receptors on some immune cells which bind to common microbial molecular patterns (e.g bacterial, viral and fungal) these toll like receptors drive many innate immune mechanisms, such as phagocytosis, cytokine release and interferon release. Each of the TLR types binds to different microbial molecules and as such are found in different locations e.g TLR4 acts on lipopolysaccharides and hence is on the plasma membrane of the cell and TLR3 acts on double stranded RNA and is found within the cell.


What are the stages of phagocytosis?

1. Pseudopodia ( temporary cytoplasm filled projections of eukaryotic cell membranes) surround microbes.
2. The microbes adhere to the phagocytes and get ingulfed
3. the microbes are ingested into phagosomes (a type of vacuole).
4. The vacuole and lysosome fuse (forming a phagolysosome).
5. the microbe is killed and digested
6. the remainder is removed via exocytosis.


How does a phagolysosome digest microbes?

The phagolysosome has a low pH and contains hydrogen peroxide (a reactive oxygen form, allowing for oxidation) and reactive nitrogen intermediates (nitric oxide). Also contains enzymes like proteases, lipases and nucleases.


What is the complement cascade? What three things does it do to bring this about and what are the three pathways?

The complement cascade refers to the 9 major complement proteins/protein complexes (C1-9) which act in sequence to remove pathogens from blood and tissues. They do this by labeling pathogens (opsonisation), recruiting phagocytes (chemotaxis) and destroying pathogens (lysis).
The three pathways are:
Classical: an antibody bound to a pathogen binds complement.
Alternative (properdin): pathogen binds to complement to surface/pathogen component.
Lectin: Carbohydrate componets of microbes bind complement. All of which amplify C3 convertase and lead to the three things mentioned earlier in the awnser.


Which complements do each of the three methods used to remove pathogens by the complement cascade? And how is each method done?

Opsonisation (labels pathogens which bind to complement receptors on phagocytes, done by C3b or labeling with an antibody), Destruction (Done by forming a membrane attack complex on the bacterial cell wall, pores in the cell which cause death, done by C9), recruitment (complement proteins act as peptide mediators of inflammation and attract phagocytes, done by C3a and C5a).


How can the complement cascade be prevented from acting on our cells?

Components of the complement cascade can be inactivated by molecules bound to host cells and as such protecting these cells from lysis.


What is lysis?

Lysis refers to the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity.


By what kind of ways can physical barriers be bypassed by pathogens?

Dry skin or eczema can cause the epidermal skin cells to be more seperated, reducing the strength of the barrier and leading to more ability for pathogens to get into the lower layers.
Cuts, burns, penetration (e.g by hookworm), puncturing (e.g by mosquitoes or needles), bites can also be used, or just going around through methods like the respiratory tract.


What methods can microbes use to resist innate immune system?

Surface molecules which resist antimicrobial peptides (staphylococcus aureus does this), evading uptake by encasing in a slimy capsule (neisseria meningitidis), prevent fusion of phagosome with lysosome (mycobacterium tuberculosis), produce proteins that inhibit interferon signalling (hepatitis C virus).