Lecture 1 - Overview of the Immune System Flashcards
What is the purpose of the Immune System?
The Immune System serves to prevent and control infections with pathogenic microbes
Where did the field of Immunology originate?
Edward Jenner discovered that Cowpox protected against Human small pol infection in 1796.
In what year was smallpox officially eradicated?
Smallpox was officially eradicated in 1979.
What are the four classes of pathogens?
Extracellular bacteria, parasites and fungi
Intracellular bacteria and parasites
Viruses (intracellular)
Parasitic Worms (extracellular)
What are the four different types of barrier in innate immunity?
Physical/anatomical
Physiological
Phagocytic
Inflammatory
What are the core components of innate immunity?
Phagocytic cells - engulf bacteria and kills virally infected cells and parasites.
Serum proteins - eg. complement, tag foreign bodies and can attack organisms.
Cytokines - interact and activated other cells.
Inflammation - the overall aim of the innate response.
NK cells - a type of lymphocyte.
What are the characteristics of Innate Immunity?
It is present from birth.
It is non-specific.
It does not develop after subsequent exposures, the response is not amplified.
Some mechanisms are evolutionarily very conserved.
It is present in lower animals.
Does an increased innate response occur for subsequent infections?
No, the innate immune response does not develop. Any subsequent exposure will trigger an identical response.
What are the lungs and digestive tract lined with?
Lungs - Cilia and Mucus
Stomach - Mucus and Acid
What barriers prevent the entry of microorganisms?
Skin, mucous membranes, stomach acid, gut flora (good bacteria)
Describe the defence within the gut against invader organisms.
There are various secretions, sebum, low pH, symbionts/commensals (good bacteria) which out compete bad bacteria and aim to defeat them. There is a flow of mucus which has two layers, a more and less viscous layer. The cilia try to propel the invaders away that get stuck in the viscous layer.
If they get through into the tissue there is the complement defence which can bind the bacteria and also macrophages which can engulf the bacteria.
Briefly describe phagocytosis.
Various cells types (mainly macrophages and neutrophils) are able to engulf, phagocytose invader molecules.
What is the overall aim of inflammation?
Inflammation is a complex series of events that results in the recruitment of more cells to the infected or damaged area.
How does the body recognise non-self or ‘danger’?
The body has a series of receptors on its own cell surfaces which can detect other molecules passing them.
On non-self molecules there are foreign flags which can be detected. There is then a ligand interaction between the receptor and the foreign flag.
How do phagocytes engulf and kill?
Phagocytes engulf and kill by proteolytic degradation and the release of oxygen radicals.
A bacterium is recognised by the phagocyte, engulfed forming a phagosome, the bacterium is then degraded.
What receptors are present on the phagocyte that recognise antigens?
Fc receptors bind antibody coated bacteria and can trigger phagocytosis.
Describe the process of phagocytosis of a bacterium.
The binding of aggregated antibody molecules to Fc receptors on the phagocyte causes the cell to engulf the bacterium.
The phagocyte first produces pseudopods, or ruffles that surround the bacterium and then fuse. The bacterium is then trapped in what is now an intracellular vesicle - the phagosome.
Within the phagocyte, lysosomes fuse with the phagosome delivering their enzymatic contents to degrade the engulfed bacterium.
What cells are the first line of defence in recognising pathogens?
Macrophages and Dendritic cells.
What are PAMPs?
Pathogen-associated molecular patterns.
What are Toll-like Receptors?
Toll-like Receptors or TLRs are composed of multiple leucine rich repeats which are useful for recognising various PAMPs.
TLRs are membrane associated proteins, some are located on the surface of the cell, whilst others are located on endocytic vesicles where they survey the degraded components of pathogens taken up through endocytosis.
Each member of the TLR family recognises different types of PAMPs.
What type of PAMP does TLR 5 recognise?
TLR5 recognises flagellin. This is a highly conserved constituent of the bacterium flagellum.
What type of PAMP does TLR9 recognise?
TLR9 recognises methylated CPG oligonucleotide motifs which are contained within the bacterial genome once the genome has been degraded within the lysosome.
What PAMP does TLR6 and TLR2 recognise?
TLR6 and TLR2 are a dimer that recognises diacyllipopetides.
What PAMP do TLR1 and TLR2 recognise?
TLR1 and TLR2 are a dimer that recognise triacyllipopetides.
