What activates naive T cells?
note; activation may include coordinated signaling (interaction of DC and T cell surface or secreting cytokines)
What is the life cycle of T lymphocytes?
- Generated in bone marrow
- migrate to thymus
- generation of a receptor for Ag
- leave in naive state to populate LN
- become activated in LN by Ags presented to them by APCs
- activated then functional polarization
What is functional polarization?
T cells take on a particular set of tasks that promote the adaptive immune response
CD8 T cells recognize which MHC class?
Class I MHC associated peptides
How are CD8 T cells activated?
by cross presentation mechanism of Ags
How does CD4 help in the activation of CTLs?
- produces cytokines that stimulate CTL differentiation
2. enhances ability of APCs to stimulate CTL differentiation
What are CD8’s stimulated to differentiate into?
Cytotoxic T lymphocytes (CTLs) and some memory cells
CD8 CTLs recognize Ags in the tissues and respond how?
by killing the target cells where the Ag is produced
What are the two signals that lead to activation of CTLs?
Signal 1 = naive CD8 recognize Ags
Singal 2 = CD28-CD80 costimulation leads to proliferation and differentiation into effector CTLs
Activated CTLs contain numerous granules called lysosomes, these contain what and what is their function?
perforin and granzymes, used by the cells to kill other cells
What cytokine do activated CTLs secrete mainly, what does this cytokine do?
IFN-gamma; activates macrophages
What transcriptional factor is involved with CTL differentiation? What is it’s function?
T-bet; regulates transcription of genes encoding perforin, granzymes and IFN-gamma
Are CD4 helper T cells more important in generation of CD8 memory T cells or in differentiation of naive CD8 T cells to effector CTLs?
Generation of CD8 memory T cells
How do CD4 helper T cells enhance activation?
they provide signal 3 in the form of cytokines
APC licensing occurs when CD4 T cell recognizes what?
Ag presented by MHC class II, delivers activating signals through CD80/CD86 and CD40
Activated CD4 Th cells express what? what do they bind to?
express CD40L; Binds to CD40 on Ag loaded DCs
What causes APCs to be more efficient at stimulating the differentiation of CD8 T cells?
CD40-CD40L interaction which upregulates expression of CD80/CD86 on the APC
What are the cytokines involved in CTL activation?
IL-2, IL-12, IL-15, IL-21