Cytotoxic T cells

Question 1

What is interesting about CD8+ cytoskeleton?

Answer 1

They have a highly dynamic actin cytoskeleton.

Question 2

What kind of cytotoxic immune cells are there?

Answer 2

NK cells and CD8+ and Cd4+ cytotcix cells (plus iNKT cells can by cytolytic)

Question 3

How is CTL killing specific? and Fast and serial?

Answer 3

specificity through TCR and immuno synapse.
Fast through preformed granules and clonal expansion.
serial- after killing they rapidly reverse polarity to kill next.

Question 4

Changes brough about through TCR signalling.

Answer 4

changes in transcription, changes in cytoskeletal reorganistaion, changes in metabbolism.

Question 5

transcriptional programmes acivated by TCR signalling?

Answer 5

NF-AT, NFKB and AP-E1

Question 6

What does interface look like immediately after pMHC binding?

Answer 6

they form villi, filopodia with TCRs at the tip.

Question 7

What is immuno synpase reogansiation loking like?

Answer 7

centrosome docks to the site of signalling, granules move along microtubules. Golgi stacks lined up.

Question 8

What is the structure of the supramoluecluar activation cluster?

Answer 8

central (cSMAC): is defined by singalling moleucels e.g. lck/ PKC.
Secretion of area of granules around cSMC.
peripheral pSMAC: defined by integrins receptors (LFA-1).
Then distal dSMAC actin ring

Question 9

What is the strucutre of the CTL mTOC

Answer 9

two centrioles surrounded by pericentriolar matrix forms the centrsome (the mTOC).

Question 10

where is mTOC normally in migration vs synpase

Answer 10

normally at back of cell in europod with granules, then moves via dynamic mediated shortening to the cSMAC.

Question 11

what signalling moelcules are thought to be important for centrosome relocation?

Answer 11

Ca2+, Rac1 and PKC.

Question 12

How does actin localise in CTLs in response to pMHC binding?

Answer 12

Accumulates originally at interface and then forms a ring after which the cnetrosome moves in to centre.

Question 13

What domain in perforin is likely important for its ppolymersiation?

Answer 13

It has a complement 9 like domain (which polymerises in MAC killing).

Question 14

What perforin domain binds to phospholipid heads on target cell and what does it require?

Answer 14

The C2 domain binds phospholipid heads and requires calcium to do this.

Question 15

Is perforin pore large enough to fit granzyme through?

Answer 15

yes it is, doesn’t happen intracellularly.

Question 16

What effects does granzyme have and 3 targets?

Answer 16

Can disrupt cytoskeletal strucutres and break dwon envelope and introduce ds breaks in DNA. Also activates caspases.
e.g. lamins, tubulins and ku70.

Question 17

what symptoms do you see in FHL and what inheritance pattern does it follow?

Answer 17

You see massive infiltration of activated lymphcoytes and macrophages into oragans.
Follows autosomal recesssive inhertiance.

Question 18

Why does FHL develop?

Answer 18

Thought to be due to early viral infection and inability of CTLs to kill virally infection cells. They maintain synapse (receive no apoptotic signals) and secrete pro inflammatory cytokies.

Question 19

Two examples of mutations behind FHL, and what syndrome is the latter called?

Answer 19

mutatinos in perforin, and mutations in Rab27a - Grisellis syndrome.

Question 20

What is Rab27a in Grisellis sydrome involved in?

Answer 20

Rab27a mutations mean that grnaules stick to mirotubules and aren’t removed.

Question 21

what proteins are involved in fusion of granules with membrane?

Answer 21

SNAPREs and their chaperones e,g, syntaxin.

Question 22

What other membrnae bound receptor killing is there?

Answer 22

CTLs express FasL, induces capsase producitn as well as TRAIL.

Question 23

How does IFN-y help cell killing?

Answer 23

It will activate macrophages and NK cells. Can lower tryptophan concentration in cells to starve intracellular pathogens,. Increases MHC 1 expression.

Question 24

How do TNFa nad TNFB help?

Answer 24

Both activate macrophages and can be directly cytotoxic through TFNR1 signalling. TNF-a contributes to systemic iflammation.

Question 25

Does cetnrosome dock to the PM? Is this seen anywhere else?

Answer 25

Yes, EMs show dockig proteins to PM. Similar seen in cilia, which are also signalling centres.

Question 26

Similarities between immune synapse and cilia?

Answer 26

Both have centrosome dockign to PM and ciliary pockets are endocytic and exoctyotic like immune synpase.
Both underog Shh signalling.

Question 27

How might Shh signalling contribute ot CTL killing?

Answer 27

Shh binds ptch, releases smoothened to PM, then activates TFs like Gli. THis can activate Rac1 which leads to cytoskeletal reogranisation.

Question 28

Why are CTLs attractive in caner?

Answer 28

Their presnece assocaited with good cancer prognosis. They are specific killers, they are durable (memory cells) and they are adaptive (huge TCR diversity).

Question 29

What do CTLs recognise on tumours and what might be the problem with this?

Answer 29

They recognsise neotanitgens, but often tumours express very low levels of these.

Question 30

where has checkpoint blockade therapy been most effective?

Answer 30

In lung and melanoma where more neotantigens are present.

Question 31

What are 3 co-inhibitory receptors?

Answer 31

CTLA-4, PD-1 and LAG-3.

Question 32

Techniques to increase effectiveness of CTLs in cancer?

Answer 32

block co ihibitiory receptors (checkpoint blockade), or activate co-stimulatory receptors (CAR-T cells).

Question 33

How can tumours affect hte population of immune cells?

Answer 33

exclude them from microenviornment (coat themselves iwth CXCL12 and prevent extravasation).

• Enrich TME with Tregs, MDSCs, and M2 macrophages.
• limit T cell expansion through IDO.

Question 34

how can tumours inhibit CTL acitivyt?

Answer 34

Downregulate tumour cell MHC 1. Inhibits granzyme B with protease. Decrease their Fas expression. Reduce \tcr signalling- increase PDL (on tumour) / PDI (on T cell.