T Cell Activation (Exam 3) Flashcards
What chemokine receptor has a role in naive T cell activation via antigen presentation?
CCR7
Explain CCR7 receptor’s role in T cell activation.
-on naive T cells and dendritic cells
-bind chemokines which signal cells to move to T cell zone in lymph node (so antigen can be presented)
What 3 signals are required to activate naive T cells?
- MHC-antigen complex
- APC costimulation
- Cytokines
Why do T cells need costimulation from antigen-presenting cells to be activated?
to prevent overactivation; ensures only they activate them
MHC Class I antigens are derived from ________ proteins while MHC Class II antigens are derived from _______ synthesized proteins.
cytosolic
exogenous
T cells express ______ which binds to B7 costimulatory molecules on the APC surface, one of the signals required to activate naive T cells.
CD28
During costimulation for activation of a T cell, _____ on the T cell binds to ______ on the antigen-presenting cell.
CD28
B7 (costimulatory molecule)
What happens when a T cell encounters MHC-antigen complex but with no costimulatory molecules from an APC?
T cell becomes anergic
What happens when a T cell encounter MHC-antigen complex in the presence of costimulatory molecules?
drives proliferation + differentiation of T cells with specific effector functions
_______ on antigen-presenting cells can enhance their function and therefore, enhance the activation of T cells.
CD40
Fill in the blank for the process in T cell activation:
A naive T cell upregulates ______ ligand which binds to ______ on dendritic cell. This leads to expression of ____ and secretion of ______ which stimulates T cell proliferation and differentiation.
CD40
CD40
B7
cytokines
Which cells express CD40? Which express CD40L?
CD40: dendritic cells
CD40L: naive T cells
What molecule an antagonist of costimulation by competing for B7 on APCs?
CTLA-4
To block T cell activation, CTLA-4 competes with ______ on T cells for binding to ______ on APCs.
CD28
B7
Term for when an activated T cell recognizes antigen and undergoes proliferation.
clonal expansion
Once an infection is eliminated, the majority of the activated effector T cells undergo apoptosis so the immune system returns to __________.
homeostasis
List the 3 different T cell subsets that can be polarized.
Th1
Th2
Th17
Match which signature cytokines belong to each T cell subset:
- Th1
- Th2
- Th17
- IFNy
- IL-4, IL-5, IL-13
- IL-17, IL-22
Th1 cells activate ________ and produce _____ antibodies for what kind of host defense?
macrophages
IgG
intracellular microbes
Th2 cells activate what two cell types? Which antibodies do they produce?
mast cells & eosinophils
IgE
Th2 cells are involved in host defense against ________.
helminths
Th17 cells activate what two cell types? What response does this lead to?
neutrophils + monocytes
inflammation
Th17 cells defend the host against what?
extracellular bacteria + fungi
What are the 3 steps of polarization of T cell subsets?
- induction
- commitment
- amplification
What occurs in the induction stage of polarization of T cell subsets?
innate immune cells produce early cytokines
What occurs in the commitment stage of polarization of T cell subsets?
cytokines cause TFs to change gene expression to a specific T helper cell lineage
What occurs in the amplification stage of polarization of T cell subsets?
after T cells are activated and polarized, cytokines are produced which can drive other T cells to polarize
