T Cell Subsets Flashcards Preview

Adaptive Immunity > T Cell Subsets > Flashcards

Flashcards in T Cell Subsets Deck (33):
1

where does activation of T cells occur and why

in the nearest lymph node in order to concentrate APCs

2

where do T cells proliferate and differentiate

in the lymph node organ

3

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

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

4

which cells express CD8

cytotoxic T cells

5

what percentage of T cells are cytotoxic

30

6

which MHC class molecule do CD8+ cells bind to

MHCI

7

Why are CD8+ cells mostly activated by professional APCs

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

8

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

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

9

what percentage of T cells in circulation are CD4+

70%

10

what are the 5 subsets of Th cells

Th1, Th2, Th17, Tfh and Treg

11

which form of T cells does HIV target

T helper cells

12

How are Th cells stimulated to differentiate to Th1 cells

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

13

after stimulation, what is the action of Th1 cells

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

14

which circumstances elicit a Th2 response

parasite infection- humoural response

15

how are Th2 cells stimulated

DCs release IL4

16

what is the action of Th2 cells

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

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

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

18

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

Arthritis/Diabetes

19

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

systemic lupus erythromatus

20

what is the role of Tfh cells

B cells depend upon these to produce antibodies

21

where are Tfh cells predominantly found

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

22

what is the action of Tfh cells

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

how are Th17 cells activated

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

24

what is the action of Th17 cells

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

which sort of response is IL17 linked to

inflammatory

26

what sort of infections do Th17 cells fight against

extracellular bacteria and fungal infection

27

which auto inflammatory diseases are linked to Th17 response

rheumatoid arthritis, MS, IBS and psoriasis

28

how is Th17 response linked to auto inflammatory disease

increase in Il6,8 and TNFa are potent inflammatory cytokines

29

what is the cause of Hyper IgE syndrome

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

30

what is the role of Treg cells

suppress immune response

31

how does Treg suppress T cell proliferation

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

which transcription factor is essential for Treg cell differentiation

Foxp3

33

what is the cause of IPEX disease

polymorphisms in Foxp3 preventing Treg differentiation