Natural killer cells - Block C lecture one

Question 1

where do NK cells develop ?

Answer 1

They do not develop in the thymus - development starts in Bone marrow and then continues in secondary lymphoid organs e.g. Lymph nodes and tonsils

Question 2

What cytokines and markers are required for NK development ?

Answer 2

IL-15 from Antigen Presenting Cells such as dendritic cells and CD56 marker are required for development

Question 3

what are the ligands for NK cells ?

Answer 3

MHC class I/MHC class I-like molecules restricted

Question 4

is recognition reliant on specific antigen receptor and do they require RAG1 and RAG 2 ?

Answer 4

Recognition is not reliant on specific antigen receptor. They do not have rearrangement of their receptor genes; this is proved because if RAG1 and RAG2 are knocked out in mice there is still NK cells produced

Question 5

CD3 expressed on NK cells?

Answer 5

no

Question 6

CD56 ?

Answer 6

yes , CD56+ is expressed isoform neural adhesion factor)

Question 7

NKp46+

Answer 7

natural cytotoxicity factor, not specific to NK cells) - but no simple marker

Question 8

are the markers on the NK cell specific to it ?

Answer 8

The markers on the NK cell are not specific to just it , they are also found on other immune cells.

Question 9

role of IL-21 in development of NK cells ?

Answer 9

IL-21 cytokine induces maturation of human CD34+ cells (stem cells) into NK cells and they become different populations.

Question 10

CD56 dimCD16+ cell subset ?

Answer 10

CD56dimCD16+ cell subset that represents the majority of NK cells - 90% of blood is NK cells

Question 11

where are CD56 bright cells found ?

Answer 11

in the secondary lymphoid tissue/tissue cells

Question 12

if the NK has a high level of granzymes what would this indicate ?

Answer 12

If the granzymes are high then this could be an effector cell.

Question 13

what are the INK ?

Answer 13

the receptors on the surface of the NK cells

Question 14

what are the 2 main roles of NK cell ?

Answer 14

secrete cytokines/chemokines and influence immune response main cytokines produced are tumour necrosis factor-α (TNF-α) and interferon γ (IFN-γ)

Kill infected/transformed cells activity very like Tc BUT:

•cytoplasm has granules in it – constitutively expressed whereas Tc cells ( cytotoxic T cells) need to be stimulated before they produce granules. The NK cells are always ready for attack.

Question 15

how do the NK cells detect the infected cells ?

Answer 15

Interact with infected (virus)/malignant (cancer) cells which have reduced expression of MHC class I molecules which markers it for killing. However, human NK cells can also kill dendritic cells (DC) by apoptosis which express normal amounts of HLA molecules.

Question 16

can NK cells bind to a pathogen and kill it directly ?

Answer 16

Can only kill your own cells NOT a pathogen by direct contact. They cannot bind to the pathogen like a bacteria cell , they bind to your own cells that are infected with the pathogen.

Question 17

how do NK cells become activated ?

Answer 17

‘opposing signal’ is the method of activation

positive and negative regulators and the balance of stimulation of activation receptors and inhibitory receptors determines whether they are activated

So you have some ligands/receptors/ things on the surface that can attach to something that will activate it, and some things where a ligand engages with it inhibits it and switches off.

There’s inhibitory and activating receptors , which are signalling inside the cell and this balances decides whether a cell is activated , and can induce apoptosis in infected cells and produce cytokines and chemokines.

think of a tug of war contest

Question 18

if there are 2 inhibitory interactions and only one activating what occurs ?

Answer 18

there is no activation.

Question 19

if the cell interaction has no MHC and a primary activating interaction what occurs ?

Answer 19

loss of MHC molecules in the tumour cell which promotes cell killing and a primary activating interaction so that killing occurs.

Question 20

what does the activation signalling receptors require ?

Answer 20

activation requires receptors such as Natural cytotoxicity receptors, killer cell immunoglobulin-like receptors (KIR).

Question 21

inhibitory signalling ?

Answer 21

inhibitory immunoglobulin killer receptors (KIR) important as they recognise class Ia (HLA-A, B, C) ligands and or non-classical class Ib ligands (HLA-E)

Question 22

cytokines involved in activation ?

Answer 22

cytokines involved are IL-2, IL-12, IL- 15, IL-18, IL-21, IFN a/b - can induce cell proliferation, or NK induced cytotoxicity and/or production of IFN-g.

Question 23

when are NK cells recruited as part of the response ?

Answer 23

NK cells recruited to tissues during an inflammatory response. The NK cells move up the concentration gradient to the infection site where they are required

Question 24

what are the 2 types of receptor: inhibitory and activating binding to ?

Answer 24

The 2 types of receptors ( activating and inhibitory) are binding to the ligands on the surface of the target cell. it is the overall balance of the receptors between activating and inhibition which lead to the response. If activating, then in the diagram the granzymes are released which target the cell and apoptosis occurs.

Question 25

what is immunological synapse ?

Answer 25

Close contact required between target cell and immune cell– immunological synapse

Question 26

what allows the immunological synapse to form ?

Answer 26

adhesion molecules e.g. alpha4beta2 integrin and leukocyte function-associated antigen-1 (LFA-1) and beta1 integrins - form immunological synapse to allow contact.

Question 27

LFA-1

Answer 27

LFA-1 transduces signals which result in an NK-cell target conjugate and can be sufficient to trigger NK cytotoxicity

Question 28

nectin / nectin like molecules ?

Answer 28

belong to immunoglobulin superfamily so 2 polypeptide chains

Cellular adhesion molecules involved in calcium independent cellular adhesion

expressed on epithelial cells and help to form junctions between cells

highly expressed on tumour cells and become accessible when the structure of epithelium is disrupted.

If signal strong between the ligand and NK cell then it can result in cell cytotoxicity by NK cell

Show importance by using people with specific deficiencies to nectins shows NK cells not as active.

Question 29

what does LFA-1 and ICAM-1 result in ?

Answer 29

interaction of LFA-1 with ICAM-1 results in granule polarisation (lined up at immunological synapse)

Question 30

role of CD16 ?

Answer 30

CD16 is Fc receptor of IgG results in degranulation which stimulates antibody dependent cell mediated cytotoxicity ( ADCC). This is called opsonisation.

Question 31

granule release ?

Answer 31

Release of granules may rely on 2 signals – but the cell needs an overall activation signal.

Activation like CTL cells - involves perforin and caspase 3 activation in target cell which induces apoptosis of cell target, this results in no inflammation.

Question 32

what will short term exposure to IL-12 result in ?

Answer 32

Short-term NK exposure to IL-12 then the NK cells release lots of IFN gamma and TNF alpha and high cytotoxic activity (classed as effector NK cells) in LN - promote Th1 response

EFFECTOR NK CELL

Question 33

exposure to IL-18 from dendritic cells result in ?

Answer 33

Exposure to IL-18 (from DC cells) promotes development of CD56+/CD83+/CCR7+/CD25+ cells (helper NK cells) could be migratory NK cells which favour Th1 response

HELPER NK CELL

Question 34

3 main types of NK cell receptors ?

Answer 34

killer immunoglobulin like receptor (KIR)

Heterodimeric c-lectin receptors ( CD94 and NG2)

Natural c lectin receptors

Question 35

KIR

Answer 35

Exist as pairs inhibitory/activating receptors

• Recognise HLA A, B and C molecules in humans
• Not a KIR for every HLA type – recognise a group of molecules which suggests homology in A.A sequence to allow binding.
• what is recognised by each receptor not yet defined in some cases

Question 36

heterodimeric C lectin receptor

Answer 36

Made from 2 proteins

Made from CD94 covalently linked to a product of the NG2 gene

CD94/NG2a inhibitory

Recognise non-classical MHC-class-1 and class I molecules

Question 37

natural cytotoxicity receptors ?

Answer 37

ligand may not defined on target cell

• used in killing of tumour cells so not found on our own healthy cells
• human NK cells kill Dendritic Cells by activation of the calcium-calmodulin kinase triggered by engagement of LFA I (adhesion molecule) - results in degranulation
• block with specific inhibitor of calcium-calmodulin kinase II
• only activated NK cells can kill DC – e.g. during viral infections not our own cells
• Also can be activated by engagement of the phosphatidylinositol 3-kinase and causes ligation of NK cytotoxicity receptors NKp30 and NKp46

Question 38

DC editing ?

Answer 38

DC editing - NK cell involved in controlling quality and quantity of DC - eliminate DCs at immature stage, and therefore bona fide tolerogenic DCs - NKp30 receptor involved

Question 39

human sudy , patients with genetic mutation in beta 2 integrin ( CD18)

Answer 39

have NK cells which are less cytotoxic. No CD18 then no antibody induced cytotoxicity

Question 40

hyper IgM syndrome

Answer 40

hyper-IgM syndrome due to a mutation in the CD40 ligand gene resulted in natural killer (NK) cell deficiency. Decreased levels of immunoglobin G in the blood and normal or elevated levels of IgM. Patients have no CD56+ or CD16+ cells and no NK activity.

Question 41

Hermansky Pudlk syndrome 2

Answer 41

an autosomal recessive disease characterized by partial albinism - have NK cells with low perforin levels and NK cells have low cytotoxic activity.