Topic 1 Flashcards
Innate Immune cells recognise…
danger signals
Examples of danger signals which innate immune cells detect
PAMP’s (Pathogen Associated Molecular Patterns) and DAMP’s (Damage Associated Molecular Patterns)
What is meant by the complement system?
A collection of proteins which work together as an early warning system to fight pathogens. Some lyse pathogens, others label microbes for phagocytes to detect, and others recruit other immune cells
How is the complement system activated?
There are 3 potential pathways. The alternative pathway, the lectin pathway or the classical pathway.
How does alternative pathway work?
Complement proteins such as c3b are spontaneously produced. What these do is they bind to the amino and hydroxyl groups of microbes which cause the complement effector mechanisms to activate
How does the lectin pathway work?
Well, mannose is a common surface carbohydrate which is found on the surface of many pathogens. Because of this, Mannose binding Lectin binds to the mannose.
Mannose is an example of a
Pathogen Associated molecular pattern (PAMP)
Mannose binding lectin is an example of
A Pattern recognition receptor (PRR)
Sentinel cells include…
Macrophages and Dendritic Cells
Properties of Macrophages include
- they dont move from infection site
- talk to T cells at infection site
- Good killer
- Good all rounder
Properties of Dendritic cells include
- Migrate from site of infection to LN (lymph node)
- Talk to T cells in LN and infection site
- Doesnt kill
- Specialised in talking with T cells
Macrophages as sentinels….
They are found in all barrier tissue, they mop up apoptotic cells, remove debris and scan the environment
First danger signal comes from
DAMP’s
The first danger signal causes
Cytokines to be released and complement pathway to activate. Macrophages are ready for action
The second danger signal comes from
PAMP’s
Examples of second danger signals are
cell wall glucans (bacteria), double stranded RNA (viruses), lipopolysaccharide (lps)
PRR’s can be
Intracellular and Extracellular
During inflammation, cytokines…
are released (TNF-alpha is a good example)
Neutrophils
are recruited from blood to infection site. They conduct phagocytosis of pathogens.
When natural killer cells are called, they release
cytokines such as TNF-y which activates macrophages
What condition arises when PAMP’s act as toxins
sepsis (which can ultimately lead to septic shock)
T and B cells recognise
Antigens (Ag)
An epitope is…
The precise part of the antigen which is recognised by the T or B cell receptor
A paratope is…
The part of an antibody or T cell receptor that binds an epitope.
Regulatory T cells
Suppress the immune response at appropriate times
Cytotoxic T cells
kill infected cells
Helper T cells…
- Activate macrophages
- Cause the activation of the immune response.
- Activate further T and B lymphocytes
B lymphocyte cells…
- Neutralize microbes
- Phagocytosis
- Complement activation
How do T cells recognise antigens?
via Antigen presenting cells only
How do B cells recognise antigens?
On their own without any prerequisite
T cells recognise antigens…
using T cell receptors which bind to antigen presenting cells
B cells recognise receptors by
Either having a surface Immunoglobulin bind and interact with an antigen or secrete an antibody which can bind to the antigen
A T cell antigen must be
a protein (which is then later broken down into peptides)
A B cell antigen can be
Anything organic (and can bind in a linear fashion or discontinuous)
T cell receptor consists of…
2 chains (alpha and beta) (although T cell receptors have 1 binding site)
B cell receptor consists of
2 heavy chains and 2 light chains (and has 2 binding sites)
Antigen receptors are created via…
somatic recombination
Junctional diversity occurs by
- Having non-precise v,d, and j joinings
- addition of bases
- deletion of bases
- sequence alignment
- filling in the gaps
what is clonal expansion?
where T/B cells see their Antigens and become active, the time required to activate and expand Ag specific T/B cells is slow, which explains why adaptive immunity is slow
How does Immune evasion occur?
Antigenic variation
T and B cells cannot…
tell what they are recognising
Central Tolerance is…
a mechanism by which T and B cells which recognise self antigens are removed/ destroyed.
Self reactive T cells are removed in
the thymus
Self reactive B cells are removed in
the bone marrow
