T-cell Immunity Flashcards
(31 cards)
Kinetics to T cell response
Pathogen introduced, initially have NAIVE TCs that have not recognized Ag and have not become activated
- once recognition occurs–>clonal expansion occurs
- now have high #’s of TCs specific for Ag
- They undergo EFFECTOR response
- Once no longer needed they decline and only a few remain as memory cells
What do DC do?
They take up bacterial Ag in the skin and then move to enter the draining lymphatic vessel
- here DC waits in TC area of LN–> wait fro TCs that are traveling from the lymph/blood to LN
- TCs sample the DC for expression of Ag that it responds to
What causes DC to home into LN?
They express receptor CCR7, and LN express ligand for receptor
Ways DC process/present Ag
Multiple ways
–>can activate all effector TCs
Naive TCs
If TC doesnt encounter Ag it will leave and remain in circulation until correct Ag present
What controls migration of naive T-cells?
They express homing receptors
What are the requirements for ACTIVATING naive TCs?
Two Signals
- Ag recognition
- Co-stimulatory signal –> B7(APC)-CD28(TC)
- ->needs to be high for TC to become activated
What occurs if only Ag recognition occurs?
Unresponsiveness or ANERGY
What occurs if only co-stimulation occurs?
No effect
B7
Expression primarily limited to APCs
Activation of APCs induces B7 expression @ high levels
When isn’t CD28 co-stimulation not required?
gamma/delta TCs CD8+ T cells In presence of strong signal 1 High avidity responses **EFFECTOR AND MEMORY TCs
What are the diff APCs?
DC (express MHC 2), MO (MHC1), and B-cells(MHC2)
Are all APCs equal in presenting Ag?
NO!
DC- activate a broad range of TCs
MO and BCs - activate effector and memory cells
Proliferation/Differentiation of activated naive TCs is driven by?
IL2
- naive TCs express low affinity IL2R
- activated TCs express high affinity IL2R and secrete IL2
- binding of IL2 to high aff receptor sends signal to TC
- signal induces TC proliferation
Do other cell surface (besides IL2) change after TC activation?
Yes
What directs activated TC to distinct anatomical sites?
Differential expression of adhesion molecules
- receptors on TCs act as homing signals to guide TCs to diff places
- target organ will express ligand for receptor
What are the functional classes of effected CD4+ TCs? (5)
They all start out as THo–>and based on environement they will differentiate into certain ones
- Th1
- Th2
- Th17
- Tfh
- Treg
What is the importance of **CD40 ligand (TC)?
Critical to the ability of **CD4+ TCs to activate other cells
- in order to have effector response and activate target they have to have a COGNATE INTERACTION
- MO–>cell mediated immunity
- BCs–>humoral immunity
What is cognate interaction?
Interaction of BC with TC w/ specificity for the SAME Ag
What controls whether CD4+ cell become Th1 or Th2?
Cytokine exposure after activation
What determines the outcome of intracellular infections?
The balance between Th1 and Th2
-Th1 - cell mediated
CD8+ cells are..
Cytotoxic TCs or CTLs
CD8+ TCs activated?
Recognize Ag presented by MHC C1 and after co-stimulation they become activated and produce diff cytotoxins/cytokines
How are **CD8+ TCs activated?
Activated by **CD28/B7
-may require additional help (from cytokines)
