Innate Immunity Flashcards
What are the primary barriers?
- skin
- ear wax
- mucus
- stomach acid
Define phagocytosis
- the engulfing of pathogens by surrounding it and ingesting it.
List 3 phagocytic cells, what receptor do they express to detect pathogens
- macrophage.
- dendritic cells.
- neutrophils.
- Toll-like receptor (TLR)
What type of receptor are TLR’s? What does it recognise? Why don’t pathogens evolve not to express these? What else can they recognise?
- TLR’s = PRR (pattern recognition receptor).
- They recognise PAMPs (pathogen associated molecular patterns) and DAMPs (danger associated molecular patterns).
- they are essential for pathogen survival.
What type of chemical are TLRs? What amino acid are they rich in?
- type 1 integral membrane glycoproteins.
- they contain leucine rich repeats.
What do TLRs 1 2 and 6 recognise? You can be more specific with 2 (what disease are these molecules associated with)
- lipids.
- TLR 2 - tuberculosis.
What do TLRs 7 8 and 9 recognise?
- nucleic acids.
What does TLR 4 recognise?
- diverse ligands.
Where are TLRs expressed? Immune and non immune cells
- immune cells: macrophage, dendritic cells, B-cells (some T-cells).
- non-immune cells: epithelial cells and fibroblasts.
What does TLR 3 bind?
- ds RNA viruses
Where are TLRs on the cell?
- most are extracellular & bind from the cell membrane.
What are the 2 phagocytes?
- macrophages.
- neutrophils.
Where are neutrophils normally?
- circulating in the blood.
Where are macrophages found?
- circulating in the lymph or in lymph nodes in organs.
Where are dendritic cells found?
- found in tissues such as skin.
- they stimulate adaptive immunity by presenting antigens to t-cells.
Where are eosinophils? What do they provide defense against?
- found on mucus membrane.
- against multicellular invaders.
Where are Natural Killer cells? What do they release and what does this do? What % of leucocytes are NKs?
- lymph nodes and spleen.
- release perforin that breaks down cell membranes.
- 5-10% of leucocytes.
How does the lymphatic system aid phagocytosis?
- some macrophages reside in lymph nodes.
- dendritic cells migrate to lymph nodes after interacting with pathogens to stimulate adaptive immunity.
Describe the 5 steps of phagocytosis
- Chemotaxis: chemicals (microbes, WBC, activated complement system) attract phagocytes to site of damage.
- Adherence: phagocytes attach to the microbe/non-self material as facilitated by bound complement proteins.
- Ingestion: pseudopod (membrane protrusion) extends & surrounds microbe and fuses into a phagosome.
- Digestion: phagosome fuses with lysosome = phagolysosome. enzymes in this break down microbe cell wall, proteins & n-acids & oxidants involved with oxidative burst.
- Killing: microbe degraded, anything left is kept in residual body.
What is a pseudopod?
- a protrusion in the phagocyte membrane which engulfs microbes/non-self cells.
What is a phagosome?
- the vesicle containing microbes/non-self material once the pseudopod has fused around it.
What are interferons?
- proteins released by cells infected by a virus.
- they prevent replication and thus spread of infection.
What is the complement system?
- a process leading to a chemical cascade resulting in lysis of bacteria.
What are Iron binding proteins and how do they work?
- bind to iron which are required by bacterial enzyme action.
- therefore affects bacterial growth.
