T Cell Effector Functions Flashcards
When the t cell is activated what does it release in order to promote proliferation
Activated t cells release cytokine IL-2+ IL-2 receptor which allows for rapid proliferation of t cell
what 3 cytokine signals are important for CD8 t cell differentiation
IL-12
IL-2
Type 1 IFN
How do activated CD8 t cells kill
infected cells will produce antigens and load them on MCH1 on their surface (if epitope is found it will kill the cell)
what type of cells do CD8 t cells kill
Since CD8+ T-cells are activated by endogenous (cytosolic) antigens, they function to kill cells that already contain “threatening” antigens inside of them
what cytotoxic molecules do t cell release to kill (3)
- Perforin- forms pores in membrane that allow entry of granzymes
- Granszymes- Induce apoptosis
- Granulysin- disrupt membranes/induce apoptosis
How are killer t cells anchored to target cell
Integrins (on t cell) and ICAMS (on target cell)
What does granzymes and granulysin lead to
Activation of caspases which activate caspase DNase which causes DNA digestion + blebbing
what effector cytokines can killer t cells released when a t cell identifies associated epitope (2)
1) Interferon gamma- activation of macrophages + NK cells
2) TNFa- upregs death receptors
What is an ex of a death ligand released by activated killer t cells
Fas ligand
-bind to death receptors on target cells and induce apoptosis
When a death ligand binds to its receptor what is recruited
allows recruitment of the death induced signalling complex (DISC) which activates caspases that mediate apoptosis
why are death ligands important for immune homeostasis
required for control of the number of lymphocytes activated during an immune response leading to the contraction of ongoing response
What types of CD4 cells does cytokines TGFb, IL6, Both, IL12, IL4
TGFb- Treg IL6- Tfh Both- Th17 IL12- Th1 IL4- Th2
What 2 signals does cd4 cells need to perform its effector function
Th1 TCR binds MHC2 and antigen
Co stim
What cytokine makes TH1 t cells and what do the t cells produce
IL12
IFNy- activation of macrophages/NK/bcells
IL2- t proliferation
When Th1 binds to an affected macrophage what is done
enhances macrophage antimicrobial activity by
- accelerated lysosome to phagosome fusion
- increase prod of toxins
- upreg of MHC for antigen presentation
IL2 released by Th1 has what effect
increases proliferative capacity of activated killer t cells (cd8)
What cytokine makes Th2 cells and what effector molecules does it release/do
IL4
IL4,5,13
Activate b cells
activate esonophils
3 signals needed to activate b cells
- MHC2 + antigen binding to CD4
- Costim of CD40L (on t)+CD40 (on b)
- Cytokins IL4,5
What is the function of T cell cytokines when activating b cells
different cytokines will stim b cells to make different classes of antbodies
Activated Th2 cells release IL4, 5 what do they do
IL4- basophil + NKT cell activation
IL5- eosinophils (chronic asthma, allergy)
What cytokine activated Tregs and what is its function
TGFb
Secretes immunosuppressive cytokines such as IL12 and TGFb
What cytokine actives Th17 and what does it secrete
activated by: TGFb, IL6
releases: IL-17
What does IL17 (released by Th17) do?
induces epithelial/innate cells to release:
G-CSF- promotes granulocyte prod in bone marrow
IL8- recruites neutrophils
what type of infection is Th17 important for
important against extracellular and fungal infections + autoimmune disorders
What is the function of Follicular helper t cells (Tfh)
Important for b cell activity, differentiation, survival in germinal centre
What costims and cytokines are needed to activate Tfh
ICOS-L
Il6
What is cross presentation and what is important for
where exogenous antigens are put on MHC1 (instead of 2)
effective against viruses that don’t infect APCs
how long does primary t cell response take (inactivated to activated)
7-14 days
how many t cells will die after antigens eliminated
95%
