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Adaptive Immunity > T Cell Subsets > Flashcards

T Cell Subsets Flashcards

1
Q

where does activation of T cells occur and why

A

in the nearest lymph node in order to concentrate APCs

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2
Q

where do T cells proliferate and differentiate

A

in the lymph node organ

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3
Q

what 3 signals do APCs present to a naive T cell in order to activate it

A

MHC-TCR activation
survival signal sent between CD28 coreceptors
differentiation signal mediated by cytokines e.g. IL6, 12 and TGFb

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4
Q

which cells express CD8

A

cytotoxic T cells

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5
Q

what percentage of T cells are cytotoxic

A

30

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6
Q

which MHC class molecule do CD8+ cells bind to

A

MHCI

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7
Q

Why are CD8+ cells mostly activated by professional APCs

A

because they have a very high activation threshold so Dcs are the only cells which express sufficient B7 co receptors to bind to CD28

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8
Q

How do non-professional APCs activate CD8+ T cells?

A

They require help from Th2 cells which express the CD40 ligand which increases the APCs ability to produce B7 as well as inducing IL2 production which drives CD8 proliferation

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9
Q

what percentage of T cells in circulation are CD4+

A

70%

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10
Q

what are the 5 subsets of Th cells

A

Th1, Th2, Th17, Tfh and Treg

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11
Q

which form of T cells does HIV target

A

T helper cells

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12
Q

How are Th cells stimulated to differentiate to Th1 cells

A

once DCs have engulfed a pathogen they release IL12. This promotes differentiation to Th1

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13
Q

after stimulation, what is the action of Th1 cells

A

Th1 secrete IFNg and CD40 ligand. this hyperactivates macrophages to increase expression of enzymes and H2O2 improving its killing capabilities.
in addition cytokine release causes vasodilation to increase blood flow and access of immune cells. Il2 release promotes proliferation and IL3 instructs the bone marrow to make more cells. finally TNFa release causes macrophages to accumulate at the site of infection

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14
Q

which circumstances elicit a Th2 response

A

parasite infection- humoural response

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15
Q

how are Th2 cells stimulated

A

DCs release IL4

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16
Q

what is the action of Th2 cells

A

Il4 release optimises IgE class switching in B cells to activate macrophages.
IL5 mobilises, matures and recruits eosinophils
IL13 induces goblet cell differentiation and mucous production

17
Q

what are the 2 types of leprosy and which Th response is responsible for each

A

Th1 response leads to tuberculoid leprosy (milder) whilst Th2 response leads to the lempromatus leprosy which has a high mortality rate

18
Q

give an example of an autoimmune disease associated with inappropriate Th1 response

A

Arthritis/Diabetes

19
Q

give an example of an autoimmune disease associated with inappropriate Th2 response

A

systemic lupus erythromatus

20
Q

what is the role of Tfh cells

A

B cells depend upon these to produce antibodies

21
Q

where are Tfh cells predominantly found

A

lymph nodes - upon activation the migrate to different region of lymph node where B cells are found

22
Q

what is the action of Tfh cells

A

migrate to B cell region of lymph node and find B cells which recognises same pathogen. It then produces cytokines to allow B cell to produce antibodies

23
Q

how are Th17 cells activated

A

Docs release IL6 and TGFb . Th17 cells reinforce this by releasing IL21 in an autocrine manner

24
Q

what is the action of Th17 cells

A

they secrete Il17 to attract neutrophils as well as cause keratinocytes of the endothelium to release b defensins and IL21 to activate Nk cells

25
Q

which sort of response is IL17 linked to

A

inflammatory

26
Q

what sort of infections do Th17 cells fight against

A

extracellular bacteria and fungal infection

27
Q

which auto inflammatory diseases are linked to Th17 response

A

rheumatoid arthritis, MS, IBS and psoriasis

28
Q

how is Th17 response linked to auto inflammatory disease

A

increase in Il6,8 and TNFa are potent inflammatory cytokines

29
Q

what is the cause of Hyper IgE syndrome

A

an impaired response to IL6 which prevents Th17 differentiation resulting in recurrent infection but the absence of fever

30
Q

what is the role of Treg cells

A

suppress immune response

31
Q

how does Treg suppress T cell proliferation

A

CD25 receptor on Treg is an IL2 receptor also. Treg cells sequester IL2 which is a major proliferation signal for other T cells. - cytokine consumption hypothesis.
They also actively secrete anti-inflammatory cytokines such as Il10 and TGFb.
They have cell surface receptors such as CTLA 4 which represses APC activation level upon interaction.
Finally cytolysis kills other T cells and APCs

32
Q

which transcription factor is essential for Treg cell differentiation

A

Foxp3

33
Q

what is the cause of IPEX disease

A

polymorphisms in Foxp3 preventing Treg differentiation

Adaptive Immunity (6 decks)

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