Immunology lecture 4- eliminating pathogens that live outside of the cell Flashcards
Which intracellular bacteria cause the following diseases?
- Respiratory infections
- Legionnaire’s
- Listeriosis
- Meningitis
- Typhoid fever
- TB
- Chlamydia pneumoniae
- Legionella pneumophila
- Listeria monocytogenes
- Neisseria meningitidis
- Salmonella typhi
- Mycobacterium tuberculosis
Modes of action to kill viraly or bacterially infected cells
Cytotoxic T cells
NK cells
Macrophages
Describe now Cytotoxic T cells are activated
Binds to antigen presented on MHC class 1 molecule on dendritic cell in lymph nodes. Multiplies then leaves the lymph nodes and follows inflammatory signals to sight of infection
What are the 2 receptors located cytotoxic T cells?
TCRaB (alpha beta)
CD8 co-receptor
Which cell in the body does not present MHC class 1 receptor?
Red blood cells- has nu nucleus
What mechanism does Cytotoxic T cells use to kill infected cells presenting a segment of the pathogen on its ,MHC class 1 receptor
Apoptosis
Describe what apoptosis does to the cell
Cell digested from the inside
Cell Membrane kept intact
Nuclear blebbing occurs
Small mambrane fragments (vesicles) are shed
Nucleus is fragmented by nuclease enzymes
The fragments (apoptotic bodies) are removed by phagocytic cells
How do cytotoxic T cells initiate apoptosis?
They use lytic granules (modified lysozymes) which have 2 powerful agents
What are the two powerful agents of lytic granules?
Perforin- Forms pores in the target cells membrane
Granzymes- proteases which bind to proteins on cell membrane, enter the cell then cut up proteins in the target cell
How do cytotoxic T cells differentiate between infected and not infected cells
They conducted non specific adhesion
Grabs onto any cell using receptors. Assess if the cell has a MHC class 1 receptor presenting the same antigen.
If no, it releases the cell and looks for another
If yes it uses TCR: MHC peptide interactions to pull the infected cell closer and exert its responce
Type of cells cytotoxic T cells kill?
Infected cells and tumour cells
Are natural kill cells part of the innate or adaptive immune system?
Innate immune system
Are natural killer cells lymphocytes?
Yes
Difference between NK cells and other lymphocytes?
Do not have antigen specific receptors
Which method of cell death do Nk cells use?
Same at T lymphocytes
Perforin and granzymes
What is activates NK cell?
Cytokines
What does NK cells secrete?
Interferon gamma
How do NK cells know a cell is infected and avoid killing normal cells
Missing self hypothesis
Recognition of “self” = No killing by NK cells
Recognition of “missing-self” = Killing by NK cells
When a cell is not infected what sits in the MHC class 1 molecule?
Self antigen
How does an NK cell recognise self antigens?
When NK cells develop in the bone marrow they are programmed to identify your MHC class 1 molceule. So it goes to different cells in the body and ensures this MHC class 1 molecule is being presented
Function of inhibitory receptor and activating receptor in NK cells
Inhibitory- binds to side of MHC molecule to ensure it is present and self
What do some viruses do to the MHC class 1 molecules present on human cells? How does theis activate NK cells
They down regulate MHC class 1 so it is no longer expressed on the surface of the cell.
When the NK cell assess if the cell has MHC class 1 the answer will be no.
So the NK cell kills the cell.
Tumours work the same way
