Innate Immunity 6 Flashcards
what type of cells are NK cells?
innate lymphoid cells (ILCs)
what cells do NK cells share a progenitor with? what is the progenitor called?
share a progenitor with B and T cells
progenitor = common lymphoid progenitor
are NK cells innate or adaptive?
innate
how many types of ILCs are there? and their names?
3
ILC1, ILC2, ILC3
what are 2 differences btwn NK/ILCs compared to other cells from the common lymphoid progenitor (B and T cells)
- part of innate response
- they are not antigen specific
where are ILCs located?
in tissues, adjacent to mucosal layer
ILCs play an important role in ______ immunity
ILCs play an important role in mucosal immunity
describe the specificity of ILCs
specific for TYPE of pathogen, but not for epitope/antigen
where are NK cells located?
in tissues or circulation
what is the role of ILCs?
contribute to defense against specific pathogen
what is the role of NK cells?
directly kill stressed cells
why is it important that NK cells are in circulation?
this allows them to travel to site of infection
do ILCs and NK cells have PRRs?
ILCs don’t have PRRs but a subset of NK cells have PRRs
how are ILCs/NK cells activated if they don’t have PRRs?
activated by cytokines from DCs or other cells
what is the general role of ILCs and NK cells?
once they are activated, there is intracellular signaling which allows for the release of more cytokines to contribute to pathogen killing
what type of pathogen do NK cells and ILC1 target?
intracellular pathogens
what type of pathogen do ILC2 and ILC3 target?
extracellular pathogens
describe the role of ILC1
allows for killing of intracellular pathogens
describe a role of ILC2
increases mucous production to wash away parasite in intestinal lumen for ex.
describe a role of ILC3
recruits neutrophils to release antimicrobial peptides to kill extracellular bacteria and fungi
can ILC2 be found in circulation? what is the evidence for this (experiment)
experiment shows ILC2 can be found in lymphatic circulation
in experiment where cytokine (IL-25) was added to ilea of gut, can see ILC2 in lymphatic vessel, while no ILC2 was found in non-IL-25 treated ilea
are ILCs solely tissue residents?
NO, in some cases they can travel
how do NK cells work?
when host cells become stressed, they express stress proteins
NK cells have receptors for these stress proteins and can kill the host cell
what are 3 stressors that could cause expression of stress proteins on host cells?
- infection (main)
- cancer/tumour (malignant transformations)
- damage, other stressors
how do NK cells kill the host cell? (not receptors)
by producing cytokines that induce adaptive responses against the host cell
how do NK cell receptors change?
they don’t –> receptors are encoded in the germline
what are the 2 types of NK cell receptors?
- activating receptors
- inhibitory receptors
what do NK cell receptors recognize?
- MHC class I molecules
- MHC class I-like molecules
what does the NK cell do in a normal context?
receives activating and inhibitory signals but there are more inhibitory signals which override the activating signals and PREVENT ACTIVATION OF NK CELL –> host cell survives
what does the NK cell do in a disease context? (MOST COMMON)
lack of MHC-1 so there is no inhibitory signals –> only activating signal is received so NK cells release granules to poke holes in the cell to trigger apoptosis
lack MHC-1 bc pathogen prevents antigen presentation, so cell very damaged!
what does the NK cell do in a disease context (LESS COMMON)
host cell can express Death Receptor which is targeted by TRAIL ligand on NK cells –> cleaves pro-caspase 8 into caspase 8 and causes self-induced apoptosis
what is different about the TRAIL/DR mechanism of NK killing vs the more common mechanism?
there are no activating or inhibitory signals –> just the binding of TRAIL to DR causes apoptosis
