Jan 24 - Innate Immunity Natural Killer cells and Innate Lymphoid cells

What are natural killer cells a subset of?

Innate lymphoid cells (ILCs)

What do NK cells share a common progenitor with?

Common lymphoid progenitor with B and T cells

What kind of immunity to ILCs and NK cells provide?

Innate immunity

How many types of ILCs are there?

3 types of ILCs

What influences what type of ILC the ILC precursor will turn into?

Cytokines

Where do ILCs tend to reside?

IN tissues

What are ILCs important for?

Mucosal immunity

What do ILC1 cell fight against?

Viruses and intracellular pathogens

What does ILC2 primarily fight against?

Extracellular parasites

What does ILC3 mostly fight against?

Extracellular bacteria and fungi

Where are NK cells found?

Tissues or circulation

Do ILCs directly kill cells?

Contribute defense against specific pathogens

Which cells do NK cells kill?

Host cells

Do NK cells have PRRs?

Yes

Do ILCs have PRRs?

No (?)

How do ILCs get activated?

Need cytokines to activate and to differentiate

What do ILCs secrete?

Cytokines

Which type of ILC is not solely tissue resident?

ILC2

What can NK cells expressing receptors for self proteins be induced by?

• Infections

• Malignant transformations (Cancer)

• Other stresses

What can activated NK cells do?

Kill the altered self cell (due to tumor or infection) and produce cytokines that induce responses against the altered self cell

Do the NK cell receptors ever change?

No, they are germline encoded

What kinds of receptors do NK cells have?

Both activating and inhibitory receptors

What do NK cell receptors recognize?

MHC class I molecules or MHC class I-like molecules

Where are MHC I molecules expressed?

ON all nucleated cells

How are NK cells activated or inhibited?

MHC class I binds to inhibitor and activating receptor is bound as well to its ligand → Inhibition

If no MHC class I for inhibitor, NK cell is activated

What happens once an NK cell is activated?

NK cells kills target cells via granules that poke holes in the cell that triggers apoptosis

What determines whether NK cells are activated"?

Balance of receptors

What is another way that apoptosis can be triggered by NK cells?

Some cells express DR4 and DR5 which can bind to TRAIL on NK cells which then causes apoptosis due to active caspase 8 programming the cell’s death