Natural Killer Cells Flashcards
Where do natural killer cells originate and where are they found?
originate from bone marrow and are found in the blood, spleen, and liver.
When to NK cells migrate to tissues?
migrate to tissues only when an inflammatory reaction is underway
What receptors do NK cells have?
- Cell trafficking receptors/chemokine receptors
What are the functions of NK cells?
- secrete cytokines that are important for regulation of the immune response
- Kill abnormal cells
What do the killing mechanisms of NK cells depend on?
- Killing mechanisms depend on either perforin system or the Fas/FasL interaction
How are NK cells identified?
- by expression of CD56, CD16, and lack of CD3 (humans and mice)
- no exclusive marker but CD2+/CD8+/CD3- are used (pigs)
- CD335 (bovine)
- granules
What is the role of NK cells in innate immunity?
kill cells which are stressed, infected with virus or tumor cells - cells that have been deemed abnormal
What happens after NK cells have been activated with cytokines such as IL-2 and IFNy?
they become lymphokine activated killer cells (LAK)
What are lymphokine activated killer cells (LAK)?
highly cytotoxic cells and are a potential tool in immunotherapy of tumors
How do NK cells recognize abnormal cells?
- abnormal cell has been stressed by any means (eg: infected, transformed cell (tumor)
- Stressed cells alter the expression of certain cell markers such as MHC (major histocompatibility complex)
- MHC I chain related A (MIC A) and MIC B are highly expressed on surface of stressed/abnormal cells
How is MHC I expression changed in stressed/abnormal cells?
expression is suppressed or not expressed at all
What types of receptors do NK cells have?
- activating receptors
- Inhibitory receptors
True or False? Activation of NK cells is regulated by a balance between signals from activating receptors and inhibitory receptors.
True
What does a high level of activating receptors lead to?
killing of the target cell
True or False? In a normal cell, activating signals are usually blocked by inhibitory signals.
True - prevents their death
NK cell receptors that recognize the MHC class I molecule belong to what family?
Killer cell immunoglobulin-like receptor family (KIRs) or Killer cell lectin-like receptors (KLRs) in mice rats and horses.