Killer T Cells Flashcards
What are the two types of killer T cells?
- Cytotoxic T lymphocytes CTL
- Natural killer cells NK
Are CTLs part of the innate or adaptive immune response?
Adaptive
Are natural killer cells part of the innate or adapt immune response?
Innate
What are the two reasons are bodies need killer T cells?
- Most viruses live and replicate in cells that lack the machinery for destroying microbes
- Even in phagocytes some microbes escape from vesicles and hence cannot be destroyed
What are the three steps to granule mediated lysis?
- CTL recognises the antigen expressing target cell and is activated
- Activation results in release of granule contents through the are of contact
- Granule content kill cell and CTL detach
What are cytoplasmic granule toxins?
A membrane disrupting protein known as perforin and granzymes
Which granzyme induces apoptosis?
Granzyme B
What is perforin?
Membrane pertruding molecule that works the came way as MAC
What is the main function of perforin?
The punch hole in the membrane to allow granzymes into the cytosol of the target cell
What is Fas mediated apoptosis?
Activated CTLs express a membrane protein called FAS ligand that bind to the death receptor Fas resulting in apoptosis
Which mechanism of CTL is more common?
Perforin and granzyme B
What are the three possible reasons that CTLs do not get damaged?
- After delivering granules CTL immediately releases
- Granules are directed away from CTL during exocytosis
- Cathepsin B degrades perforin molecules that come in the vicinity of the CTL membrane
What cytokine do CTLs produce?
IFN gamma
What is unique of natural killer cells?
They are ready to join the immune system as soon as they have developed without further differentiation
Where are natural killer cells derived from?
Bone marrow
How do natural killer cells detect pathogen infected cells?
Germline DNA encoded receptors
What type of cytokine do natural killer cells release?
IFN gamma
What are the two outcomes possible when a natural killer cell detects a cell?
- Healthy normal cells –> Blocked
- Infected/damaged –> NK cell activated
How is natural killer cell function regulated?
By a balance between signals that are generated from activating receptors and inhibitory receptors
What do inhibitor receptors in natural killer cells detect?
MHC class I
What is missing self triggering of natural killer cells?
When the cells may lose expression of MHC class I molecules
What is stress induced self triggering of natural killer cells?
When stressed cells up regulate activating ligands for natural killer cells thereby overcoming the inhibitory signal
What is antibody dependent cell mediated cytotoxicity?
Engagement of CD16 by antibody coated target cells which activated the NK cells to synthesis and secret cytokines and release granules
