Coevolution of Innate and Adaptive Immunity: NK cells
15 important questions on Coevolution of Innate and Adaptive Immunity: NK cells
Which three models are there for co-evolution of both immunity systems? Which one is the most likeliest?
- With the emergence of adaptive immunity, innate immunity stops evolving
- Independent evolution of innate and adaptive immunity
- Coevolution of both immunity systems
--> NK cells are proof of coevolution becase they seem to be active in both immune responses and in primary and secondary responses
Why is it hard to label NK cells to either one of the immune responses?
Where do NK cells develop and where do they stay once matured?
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What happens to individuals with NK deficiency?
- Association between NK cell receptor and the disease outcome of HIV
How do NK cells detect "missing-self"?
A cell lacks HLA-E (aren't enough) and does not present antigen to the NK cell it is unhealthy and thus induced the NK cell to kill the virus-infected cell or tumours
Viruses down-regulate the MHC I expression --> no inhibition by HLA-E, NK cells detect infection --> “missing-self” detection
What type of receptor do KIRs look like and what do they bind to?
KIR bind to the polymorphic site of the MHC molecule → KIRs footprint overlaps with the TCR binding site. KIRs bind to HLA-A, -B, and -C (also highly polymorphic) --> HLA-C are good ligands for KIR but there are only a few for HLA-B
How are NK cells educated to distinct healthy cells from infected cells?
If the target cell does not have this same MHC molecule, NK cells will bind to other receptors on the target cell and release cytokines to induce apoptosis
Explain what primitive/older T cells are and what they do.
- λδ T cells: recognize their ligands on MHC-like molecules --> lipids and phospholipids
- NKT cells: both have T cell and NK receptors: activate NK, Neutrophils and B cells, thus produces a wide variety of cytokines. Uses CD40 to activate the B cells in the germinal centres --> produces lipids as receptors
- Mucosal associated invariant T (MAIT) cells: lower TCR diversity and interact with MR1 molecules on dendritic cells --> develop in the thymus and have an alfa-beta TCR
What three mechanisms ensure that only infected cells are attacked by NK cells?
- Intimate contact with target cells is required
- No single receptor-ligand interaction induces cytotoxicity, but instead many combinations of receptor-ligand interactions influence the decision to kill
Name two characteristics of NK cells
- They tolerant of healthy cells
False:
- They all express the same selection of activating and inhibitory NK-cell receptors
Should a cell experience loss of all surface MHC class I expression following viral infection, what would be the impact on NK-cell activity?
Hat type of HLA classes are not expressed on extravillious trophoblasts (cells of th foetus)?
During NK cell education, which molecules do play a role?
- HLA-A
- HLA-B
- HLA-C
--> not HLA-G
What are two differences and two similarities between cytotoxic T cells (CTLs) and NK cells?
- Secrete cytokines
- Use MHC class I molecules for their development
Differences:
- Express CD3 component
- Rearrange their receptors
What is recognized by gamma-delta T cells?
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