L7: T cell Effector Mechanisms Flashcards
Do activated CD4 T cells have L-selectin on their surface?
Yes. L-selectin lets T cells move into secondary lymphoid tissue. T helper cells are necessary for B cell activation in secondary lymphoid tissue
Is VLA-4 present on CD8 activated cell surfaces?
Yes.
What does the Fas ligand do?
It binds to infected cells and helps promote apoptotic death.
What would the presence of many active CD8 T cells promote: TH1 or TH2 differentiation?
TH1. CD8 T cells secrete IFN-gamma, which is a strong promotor of TH1 differentiation. TH1 cells are also important in activation of new CD8 T cells.
What is CD40 ligand?
helps activate macrophages and B cells by binding to CD40 on their cell surfaces
What will IL-4 and IL-5 cause a TH0 to differentiate to?
TH2, which will generally activate B cells to make antibodies.
What would IL-4 cause a TH0 to differentiate into?
TH2
What would IL-12 cause a TH0 cell to differentiate into?
TH1
What would IFN-gamma cause a TH0 to differentiate into?
TH1
What produces IL-12?
APCs (antigen presenting cells)
What do Treg cells do?
they down-regulate activation of naive T cells by producing large amounts of IL-10 and TGF-beta
What is T-bet?
A transcription factor in TH1 cells that promotes production of IL-2 and IFN-gamma
What is GATA-3?
A transcription factor in TH2 cells that promotes production of IL-4 and IL-5
What is the transcription factor that promotes IL-2 production in TH!?
T-bet
What is the transcription used by Treg cells to promote TGF-beta?
FoxP3 is the transcription factor
What do granzymes do?
they re serine proteases which activate apoptosis once in cytoplasm of the target cell
What is granulysin?
secretion of cytotoxic T cells that has antimicrobial actions and can induce apoptosis
Do granzymes travel through perforin pores?
no, they are too big for the pores.
The pores damage the membrane and the host cell responds by endocytosing it. Granzymes bind to cation-independent mannose-6-P receptor (CI-MPR) and are taken into the cell during the endocytosis.
Reparative endocytosis.
How does Fas ligand kill cells?
it activates the caspase cascade.
How do CTLs focus their killing capability to only one cell and not the adjacent ones?
They polarize themselves so as to force the granule contents to dump in one specific site.
Which type of T helper cell activates macrophages?
TH1 using CD40 and IFN-gamma. B7 and MHC class I and II are upregulated after that.
What is the only way a TH1 cell can kill another cell?
Using Fas ligand, they can kill infected, worn out macrophages.
What will IL-3 and GM-CSF released from a TH1 molecule do?
promote differentiation of macrophages in the bone marrow.
What does CKCL2 do? Where does it come from?
It is released by TH1 cells and causes macrophages to accumulate at site of infection
What do TNF-alpha and LT when released from TH1 cells?
they induce macrophage adhesion and exit from blood vessels at sites of infection
What does TNF-alpha do to macrophages?
Activates macrophages.
Induces NO production
What does GM-CSP do to hematopoietic cells?
increases production of granulocytes, macrophages and dendritic cells
What are JAKs? STATS?
Janus Kinases.
When cytokine receptors on cells are activated, JAKs become activated and phospharylate themselves. This attracts a STAT, which binds to the JAK and gets phosphorylated. The phosphoyrlated STAT then binds to another phosphorylated STAT and forms a dimer. This dimer then moves into nucleus and binds to DNA to initiate gene transcription
How do granulomas form?
occurs when microbes resist destruction by macrophages. The function is to prevent dissemination of microbe.
IFN from TH1 cells induces granuloma formation.
A defect in CD40 will prevent granuloma formation.
How does CD40 deficiency prevent granuloma formation?
without CD40, T helper cells can not activate macrophages.
