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30 Cards in this Set

  • Front
  • Back
Where in the body are naive T cells activated?
Lymph nodes and spleen.
What cells in the spleen are responsible for initiating the adaptive immune response against blood borne pathogens?
Dendritic cells (laangerhans)
If a pathogen is received via receptor mediated endocytosis, what MHC molecule will be involved and what Naive T Cell will be activated?
MHC Class II - CD4+ Tcells
If a pathogen is received via macropinocytosis, what MHC molecule will be involved and what Naive T Cell will be activated?
MHC Class II - CD4+ Tcells
During a viral infection, what MHC molecule will be involved and what Naive T Cell will be activated?
MHC Class I - CD8+ Tcells
If a pathogen is received via cross presentation after phagocytic or macropinocytic uptake (involves a virus), what MHC molecule will be involved and what Naive T Cell will be activated?
MHC Class I - CD8+ Tcells
If a pathogen is received via transfer from incoming dendritic cell or resident dendritic cell, what MHC molecule will be involved and what Naive T Cell will be activated?
MHC Class I - CD8+ Tcells
Where in the lymph node are Dendritic cells located? Macrophages? B cells?
Dendritic cells are in the Tcell areas, macrophages are all over, and B cells are in the follicles.
From where do T cells enter the lymph nodes?
From lymph and blood
What molecules (3) initiate rolling of T cells so they can cross into a lymph node?
L-selectin, CD34, and Glycam-1
What signals all a t lymphocte to stop rolling and squeeze through cells into a lymph node?
LFA-1 becomes activated (on T cell) and binds ICAM-1 (on epithelium)
How many signals are required for Naive T Cell activation and what are these signals?
Two are required. TCR + CD4/8 binding to MHC + Ag and a costimulatory signal of CD28 (on T cell) binding to B7 (on dendritic cell).
What molecule shuts down the Tcell response? How does it work?
CTLA-4 - turns off costimulatory signal by binding B7 with higher affinity than CD28.
How does a TCR signal once it receives both signals? What is the name of the motifs?
CD3 molecules and Zeta chains contain ITAM motifs that phosphorylate Lck, Fyn, and Zap 70. This cascade continues until an effector function is reached.
Once the Tcell is activated, what molecule signals the Tcell to proliferate?
The Tcell produces IL 2, which signals itself to proliferate (autocrine).
How do many immunosuppressant drugs work on Tcells?
By inhibiting IL 2 production, which stops Tcell proliferation.
If a Tcell encounters an APC with MHC:Ag and costimulatory signal, what happens? What about if it only receives MHC:Ag and no costimulatory signal? How about just a costimulatory signal?
Both Signals: Activation of Tcell
Just MHC:Ag: Anergy
Just Costimulatory: Nothing
List the stages of CD4 Tcell Activation
Naive CD4 --> Proliferating Tcell --> Immature Effector Tcell --> Th1, Th2, or Treg cell.
What is the function of Treg cells?
They suppress the immune response.
What is the function of Th17 cells?
Neutrophil mobilization
What interluekin promotes Th2 cell development? What is the fxn of Th2 cells?
Il-4; Th2 participate in the general activation of Ig secreting B cells. Think of IgE Allergy response.
What molecules promote Th1 development? What is the fxn of Th1 cells?
Il-2 and IFN-gamma. These cells activate B-cells, macrophages, and production of opsonization molecules; help to kill intravessicular bacteria.
What molecule leads to the development of Treg cells?
TGF-Beta
What is the appropriate Tcell response to M. Leprae? What is the inappropriate response that leads to Lepratamous Leprae?
Th1 CD4 response results in a normal, non dangerous Tuberculoid Leprosy. In Lepramatomous Leprosy, Th2 CD4 cells are produced instead.
What are the three ways a CD8 Tcell can be activated?

What is the take home message?
1) Direct activation by a virus infected Dendritic cell due to high levels of B7 comstimulation.
2)CD4+ Cell can be stimulated by APC, which in turn stimulates the APC further to express more B7 - now CD8 activated
3) APC can stimulate CD4 to make IL2 and CD8 to Make IL2 receptors. Binding of the CD4 IL2 to the CD8 IL receptor activates the CD8 cell.

Take home message: very stringent activation requirements for CD8!
Why does CD8 T cell activation have such stringent requirements?
B/c once activated, no secondary/costimulatory signals are needed and the cell becomes very, very destructive and self proliferates via IL2 (recall autocrine fxn).
What are the two ways Cytotoxic CD8 T cells kill target cells?
Lytic Granules and Fas Ligand
Lytic granules lyse the cell membrane and Fas Ligand induce apoptosis.
How does the Cytotoxic T cell rearrange/orient its' cytosol to release lytic granules?
It orients it golgi and cytoskeleton to face the doomed cell.
What disease is caused from a deficiency in Fas?
ALPS - b/c without fas/fasL unwanted self lymphocytes (self reactive) aren't cleared from the immune system and clog up lymph nodes.
In what tissues are naive T cells found? Effector T Cells? What is the other major difference b/t naive and effector T cells?
Naive T cells are only in secondary lymphoid tissue, Effector T cells are found in the periphery.
Effector T cells have a reduced need for costimulation to become activated.