Activating the immune system Flashcards
What are 4 important switches for initiating the immune system?
- the Danger signal
- Professional antigen presentation
- MHC
- Co-Stimulation
through which two molecules does the immune system detect danger?
- Pathogen-associated molecular patterns
- Damage-associated molecular pattern molecules
What are some examples of PAMPS?
- Glycans and glyconjugates
- Bacterial lipopolysaccharides
- Endotoxins found on the cell membranes of gram-negative bacteria
What are some examples of DAMPS?
Endongenous danger signals such as heat shock proteins
Extracellular danger signals such as neuromodulators and cytokines/ interferons
What releases DAMPS?
Released by stressed cells undergoing necrosis but not apoptosis
What are some examples of non-protein DAMPS?
- ATP
- Uric acid
- Heparin sulfate
- DNA
What are TLR’s/ Toll-like receptors?
a type of PRR that play a crucial role in the initiation of the innate immune response by detecting potential harmful pathogens
What are TLR’s specialised in?
The recognition of conserved molecular structures in bacteria, viruses, fungi and parasites
What are the three main pathways that are activated by TLR’s?
- MAP kinase pathway
- NFkB pathway
- IRF pathway
What are the three main populations of antigen presenting cells
- dendritic cells
- Macrophages
- B cells
What kind of APC’s can activate naive T cells and trigger a primary immune response?
Dendritic cells
What kind of molecules do dendritic cells express on their membranes?
Class II MHC
these can deliver a costimulatory effect which are important for TH Cell activation
What is the function of dendritic cells
To trap, process and present antigen cells of the immune system
To kill any pathogens they encounter
What is the dendritic cell mechanism of killing?
- they produce NADPH oxidase and can kill invaders by mounting a respiratory burst
What is* antigen processing*
transforming large proteins into antigenic peptides (epitopes) within the cells
What is the function of MHC receptors?
proteins that share the task of presenting peptides on the cell surface for recognition via T cells
What is an epitope?
Regions of the proteins that can trigger a cellular immune response mediated by T or B cells
What do T cell epitopes bind to?
they bind to T cell receptors
What do B cell epitopes bind to?
They bind to antibodies or B cell receptors
What is the definition of cross-presentation
The presentation of exogenous antigens on MHC class I molecules, known as cross-presentation, is essential for the initiation of CD8+ T cell responses.
What are the three signals that can contact a naive T cell?
- T-Cell receptor recognising the antigen
- a co-stimulatory molecule such as CD28
- Cytokines
What can happen to a T-cell if it does not receive the second signal
T cell becomes mainly unresponsive/ anergic or dies
Where are MHC type I complexes usually found?
on the outside of almost all nucleated cells
Where are MHC type II molecules usually found?
they are mainly expressed on the outside of APC’s such as macrophages or dendritic cells
What type of T cell recognises MHC type I molecules?
T-Cytotoxic
What type of T cell recognises MHC type II molecules?
T-Helper
What is the structural difference between an MHC I and MHC II molecule?
MHC I contains an alpha chain and a smaller B2 microglobin chain
MHC II contains an alpha chain and a beta chain
What are some examples of co-inhibitory molecules that terminate the T Cell response?
CTLA-4, PD-1
What PRR actives NFkB
NOD proteins
What does the MAP kinase pathway lead to?
Pro-inflammatory cytokines, such as IL-6 TNF-a etc.
What does the NFkB pathway lead to?
Chemokines which attract other cells to the site of infection
What does the IRF pathway lead to?
Type I IFNs which are involved in anti-viral responses
How does the dendritic cell do cross-presentation?
It picks up the virus infected cell containing the MHC-1 molecule, The viral antigen enters the cytosol
displays the MHC I molecule on the outside
