NK cells Flashcards
What percentage of circulating lymphocytes are NK cells?
5-10%
Give a brief description of NK cells.
Lack specific Ag receptors and memory (has been disputed).
Help regulate innate/adaptive immunity by cytokine secretion.
Recognize and destroy path inf cells and tumour cells.
Proliferate earlier than CTLs
How and where are NK cells selected?
Explain the term for NK cell selection and how it works.
They are selected by interactions with stromal cells in the bone marrow.
Licensing: means it doesn’t automatically get the potential to kill unless it has had a prior interaction with a healthy cell via MHC I/inhibitory receptor.
Define anergy.
A hyporesponsive state.
What is the defining trait of NK cells?
How does this work?
The expression of a set of activating and inhibiting receptors.
The sum of receptor signalling determines whether to kill a target or not.
What is the CD# of NK cells?
CD56 - NK cells lack NK1.1
Who has more NK cell receptors, humans or mice?
Mice do, that we know of.
Describe the NK missing self model.
Where is this most often found?
normal cells presend both ligands for activating the NK cell (killing receptors) AND MHC class I molecules which inhibit the NK killing. Viruses may inhibit MHC expression which makes those cells targets for NK cell activation. Tumours may also lose MHC I.
Describe how NK cells recognize tumours.
Tumours may lose MHC I expression or the stressed cells of the tumour growth may just upregulate the killing ligands for NK cells = tumour elimination.
How do NK cells interact with DCs?
How do these interactions affect the NK cells?
Ag specific activation: Activating NK cell receptor-ligand interaction, DC costimulation, pro-inflammatory cytokines = cytokine secretion and clonal-like expansion.
Ag non-specific activation: By IL-12 and Type I IFNs via DC/pDC = cytokine secretion but no clonal expansion.
Which is more potent in terms of cytotoxicity and cytokine secretion, NK or CD8+ T cells?
NK cells are
Briefly discuss NK cell memory and the evidence for it.
NK cells are of the innate immune system but there is evidence that they have memory.
- educated development
- Ag specific receptors
- Clonal expansion
- long-lived memory cells
Discuss NK cell killing.
NK cells induce apoptosis. NK cells use mechanisms similar to CTLs.
- Release perforins/granzymes at junction
- Engage death receptors on target cell
- Secrete IFN gamma to induce MHC I on target cell for CTL detection
How do NK cells use SMAC?
Forming a SMAC allows the NK cell to directly transfer cytotoxic medators to the target cell.
Perforin: punctures holes in target cell membrane.
Granzyme B: cytotoxic molecule inducing apoptosis in target cell
