Flashcards in 6 T Cell Antigen Recognition and Activation Deck (68):
What are T cells activated by?
What is the overview of T cell activation?
1. Adhesion to APCs
2. Activation Signals
3. T cell differentiation
4. T cell proliferation
What are the first T cell molecules to bind to APCs?
LFA1 to ICAM1
What does LFA1 binding to ICAM1 allow?
TCR/CD4 and 8 binding to MHC
What sends signals to tighten the LFA1/ICAM1 binding?
TCR/CD4/8 binding to MHC
What is the signal cascade from TCR/MHC complexes?
What is the first signal of activation?
What is the second (costimulating) signal of T cell activation?
B7 binding to CD28
If B7 comes before TCR/MHC binding and CD3, what happens?
Nothing, cell does not activated
What two signals does a T cell need to activate?
What happens to the T cell if the B7 does not bind after CD3 signal goes out?
What three signal pairings do T cells need to recognize an antigen?
What one signal pair does a T cell need to proliferate?
IL2 and IL2Receptor
What is the difference between naive and mature T cell IL2R?
Mature IL2R has a higher affinity
How does the body create tolerance for some activated self-recognizing T cells that escape the thymus negative selection?
B7 is required for costimulation and needs ot be induced in APCs during infection
Thus, B7 levels remain low during health and CD8s do not kill everything even if MHCs are presented.
What signal caused T cell death if it is absent after MHC recognition?
Why do autoimmune reactions occur during infections?
Macrophages present self-peptides and antigen peptides to T cells
When is the only time T cells should proliferate?
Which type of T cell requires more signaling?
What three ways can a T cell be activated?
1. DCs activate T cell
2. APC presents. T cell activates APC. APC activates T cell.
3. APC activates CD4 to make IL2 and CD8 to make IL2R. CD4 activates CD8
What is different about a fully differentiated T cell?
1. no Costimulator required
2. Adhesion Molecules are different
What are the three main types of armed effector T cells?
CD4: Th1 and Th2
What CD8 enzyme makes holes in membranes?
What CD8 enxyme enters pores in membranes to cause apoptosis?
What signal cascade do granzymes and granulysin use?
What are the main CD8 cytokines?
What is the main function of CD4 Helper T cells?
To induce antibody class switching in B cells
What actives CD40 on macrophages?
What is special about Th1 CD4 T cells?
Activate Macrophages in addition to B cells
What is notable about Th2 CD4 T cells?
Activate B cells only
What makes macrophages better killers?
CD40 binding of T cell IFNy made by Th1 cells
What signals Th1 formation from CD4 T helper zero cells?
Why would Th1 cells need to be formed?
Viral infection: T cells needed to order B cells to make Viral based antibodies
What signals Th2 cells from CD4 Helper Zero cells?
IL4, IL5 (makes GATA-3 transcription factor)
Why would CD4 helper T cells form?
In response to an extracellular Infection, since they respond to MHC class II bound peptides from the endogenous antigen presentation pathway
Why would CD8 cytotoxic T cells form?
In response to an intracellular (viral) infection, since they respond to the MHC class I peptide produced from the cytosolic antigen pathway of proteosomic cleavage.
What are all helper T cells originally?
T helper zero cells
What do T Regulatory cells express that is unique?
FoxP3 transcription factor that increases IL10 and TGF-B to decrease cell response to infection
What do T Regulator cells do?
Decrease CD4 and CD8 response to infection
What two big factors determine Helper T cell class?
What does high concentration of antigen likely mean?
Intracellular (viral) infection
What does high concentration of antigen promote?
What does low concentration of antigen mean?
Extracellular (bacterial?) infection
What does low concentation of antigen promote?
Th1 cells are best at producing cytokines for handling what type of infection?
Th2 cells are best at producing cytokines for handling what type of infection?
What are Natural Killer cells?
Cells that kill viral infected cells
Cells that make Interfuron-Gamma to induce Th1 production and Interleukin 4 to induce Th2
What NK signal makes Th1?
What NK signal makes Th2?
Viruses cause Dendritic Cells to make what to turn up NK cell IFN-y secretion?
What do NK cells secrete to induce Th2 cells?
IL-4 in response to worms
Where are T Helper 17 cells found?
Mucosal epithelium inflammation
What do T Helper 17 produce to activate neutrophils?
IL 17 activates what?
What downregulates Th2 development?
What downregulates Th1 development?
What downregulated both Th1 and Th2 development?
T Reg cells
Adaptive responses never happen where?
At the site of infection
Adaptive responses only happen where?
Where to naive T cells live?
T cell zones of secondary lymph
B7 binds to what receptor on T cells?
B cells are unique as APCs because they bind what type of antigen?
If a T cell is not activated by a DC, what else must also likely be present?
Both CD8 and CD4 cell types
What do activated T cells express that keeps them at the infection site?
VLA4 adhesion molecules
What do activated T cells not express that keeps them from recirculating into the lymph?
What signal downregulates Th2 cells?
What produces IFN-y to downregulate Th2 cells?
NK and Th1