T cell Flashcards
What do mature naïve t cells express?
- Cd4/ CD8
- cd28
- mhc/ HLA class 1
- tcr complex with cd3 and gama
- LFA1 and VLA4 adhesion molecules
- chemokine receptor ccr7
Where are T cells activated? What is the only cell that activates naieve t cells?
In the lymph nodes by dendritic cells DC cells
What do B cells and macrophages activate?
memory t cells
what do CD4 cells activate
b cells and macropahges
Decribe dendritic presentation to T cells?
- antigen is captured and DC cell is activated when it puts the antigen on its MHC
- looses adhesive markers that keeps it in the tissues and upregulates CCR7 (found in the lympatic endothelium)
- increases expression of MHC and CD80 (B7)
- TRAVELS TO secondary tissue and matures as it migrates
- presents ag to t cells
Native t cells enter lymphnodes across what?
High endothelium venules in the cortex of lympoid tissues
if t cells dont encounter a specific ag in a lymphnode what happens?
they leave the node through the lymphatics and travel down the chain to the next lymphode.
TCR antigen regocnition changes what?
integrin conformation on T cells from low to high affinity. This allows for a strong immune synapse.
Decribe the T cell activation steps
1) T cell regongizes antigen (frist signals)
second signals:
2) this causes CD40 L expression to be upregulated on T cells to bind to cd40 on APC cells (consititivley expressed)
3) expression of B7 (cd80) is upregulated on APC now to bind to CD28 on T cells which is consitivley expressed
4) dendrdic cell will release IL12 which will enhance T cell proliferation and differentiation
immuno synapse
T cell activation
- initation of formation of the immunologic synape
- then activation of ITAM motives will cause LCK (src kinase associated receptor associated with cd4 and 8) phosprorlyate and activates tyrosine kinase zap 70 (that is assocaited with gama chain) which will have a bunch of down stream effects sitmulating nfkb
ANERGY
-a t cell recgonizes antigen without binding of costimulatory ligands or cytokine support will not be activated. They will become unresponsive or anergeic or tolerant….
How does a t cell promote proliferation?
- resting T cell have an IL2 on their receptor that is low affnity
- once you are fully activated the DENDRITIC cell will release IL-12
- this will cause the t cell to produce IL2 and the expression of high affnity chain for IL2 is put on the sruface with the intial complex
- the binding of IL2 to high affinity IL-2R promotes cell prolif and differentiation
What is the IL-2a chain?
put on with the other il2 receptors, and it is also known as cd25
How do you trap t cells
- t cells recognize antigen in a space thus it needs to chill there to be functionally active and activate b cells
- we have transient activation of CD69 which binds to s1pr TO IMPAIR migration (pulls in S1PR into the cell)
- s1pr binds to s1p normally which is in the blood and lymph thus when cd69 is bound to it it is taken up via endocytic vessicles and cant respond to s1p
- 5 days after the arrival of the antigen, the activated effector cell emigrates from the lymph node into the periphery
cytokine influence of Th development
Differntaion into Th subsets are dictated by the cytokines present.
Th1
- IFN gamma or IL-12 stimulate it
- targets macrophages for intracellular pathogens defense
TH2
- IL 4,5,13 make it
- targets eosinophils: will activate esnophils, mast cells, alt macrophages
- host defense against helminths
T helper 17
TGF-B, IL-17 and IL22 makes it
-targets neutrophils used for extracellular bacteria and fungi defence
during cross presentation what does CD4 to for CD8
shits out IL-2 which stimulates colonal expansion and differentiation.
What is the homing receptor for Naieve t cells
- L selectin and L selectin ligand (on endothelial cell)
- LFA-1 (b1 integrin) and I cam 1 (on endothelial cells)
What is the homing receptor for activated T cells
E and P selectin ligand and E and P selectin (on endothelial cell)
-LFA-1/VLA-4 (beta one and two integrin) and Icam/vcam 1 (on endothelial cells)
