Lecture 6 - The immune system Flashcards
What is commensalism?
One organism benefits, and the other is unaffected
What is mutualism?
Both organisms benefit
What is parasitism?
One organism benefits at the expense of the other
What is a pathogen?
An organism that causes disease
What is an antigen?
A molecule capable of inducing an immune response
How does the immune system protect against pathogens?
1) Mucosal barriers (Physical barriers) Skin, respiratory tract, intestines
2) Innate Immune System
- Immediate, acts within minutes
- Recognises foreign pathogens via germ-line encoded receptors
- No memory
3) Adaptive Immune System
- Takes days to develop
- Highly specific requiring sophisticated rearrangement of receptor genes
- Generates memory
What is the spleen?
95% the blood supply filters through the spleen in 3 minutes
Key role in removal of damaged red blood cells
Highly organised structure that has areas rich in immune cells (white pulp) and areas rich in red blood cells (red pulp)
Describe the role of the innate immune system
Immediate, acts within minutes.
Recognises foreign pathogens via germ-line encoded receptors.
No memory.
Antigen non-specific (this means not highly specific)
Often phagocytic cells e.g. macrophages.
Detect ‘particulate’ material and seek to scavenge / remove.
Aided by a limited number of receptors that recognise broad ‘molecular patterns’ that are not present in eukaryotes.
Describe the role of macrophages
Macrophages induce inflammation through the release of soluble factors (cytokines and chemokines)
Macrophages efficiently phagocytose (engulfment) of antigens (bacteria)
Are the first line of defence
Macrophages are found in all peripheral tissues
Describe the role of neutrophils
Most common white blood cells in blood
Migrate rapidly to site of inflammation
Phagocytic cell ingesting and killing bacteria
Release granules containing toxic components
What is the adaptive immune system?
Takes days to develop
Highly specific requiring sophisticated rearrangement of receptor genes
Generates memory
Antigen Specific (this means highly specific)
B and T cell express Antigen-specific receptors:
Antibodies (Ab) found on B cells (soluble, or membrane)
T cell receptor (TCR) found on T cells
Both are highly variable so can recognise many different antigens.
Each Ab and TCR specificity confined to a single clone.
Following activation of their antigen receptor B- and T-cells expand, mature, and differentiate to highly specialised cell populations
How are B cell and T cell antigens different?
Abs recognise the 3D shape of the antigen, they can react to proteins and carbohydrates.
TCR only recognise protein in broken down form (i.e. as peptides)
Describe the role of dendritic cells
Phagocytic cells that degrade pathogens
Characterized by the presence of long dendrite process
Main role is not in the clearance of pathogens
Main function is the activation of the adaptive immune response
Migrate from peripheral tissues to the lymph node
Dendritic Cells actively survey peripheral tissues
Describe the role of the lymphatic vessel network
The way that cells move in the immune system is largely through the lymphatic system
There are a lot of lymphatic vessels in the skin - once a dendritic cell becomes activated it goes to the nearest lymph node - this happens by infiltrating the lymphatic vessels and draining to the lymph node
(Incidentally the lymphatic system is also often how cancer cells metastasise into different tissues)
