Defence against bacteria - Adaptive immunity - CD8+ T-cells
10 important questions on Defence against bacteria - Adaptive immunity - CD8+ T-cells
What is the function of CD8+ cells in defense against viruses?
o Trigger apoptosis of infected cells (TNFa and FasL)
o Secrete soluble factors: IFN-gamma and TNFa
How is a CD8+ T cell activated?
Signal 2: Co-stimulation with the binding of CD80/CD86 to tCD28.
Signal 3: extra cytokine signals IL2 and IFNy that come from the Th1 cells.
How can naïve CD8 T-cells differentiate into effector cells without the use of CD4 T cells?
In some viral infection only the dendritic cell is enough the produce IL-2 required for the differentiation into CD8+ T cell.
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How does a CD4 T-cell co-stimulate the activation of the naïve CD8 T-cell?
The CD4-T cell binds to the APC cell and gets activated which induces the expression of CD40L and IL-2. The APC is stimulated through CD40, and this increases B7 and 4-1BBL and those substances both co-stimulate naïve CD8 T cell from inside the APC cell.
Why is cross presentation necessary?
When a virus only infect the epithelial cells, the APC cells needs to present the viral antigen on their MHC-I molecule to activate the CD8 T-cells.
How does a cytotoxic T-cell kill?
2. Viral peptides are displayed via MHC-I class molecules.
3. TCR and CD8 binds to a MHC-1 class molecule this activates the T-cell
4. Membrane vesicles with granzymes and perforins (complex with serglycin) will be released directly to the surface of the target cell.
5. The perforin facilitated the delivery of granzymes into the cells. ]
6. No it can travel to the next cell that presents a antigen on the MHC-I class molecule.
In which two pathways can a cytotoxic T cell kill?
Via the extrinsic and intrinsic pathway. The extrinsic pathway is mediated by death receptors while the intrinsic pathway is induces in response to apoptosis stimuli or lack of growth factors.
How do granzymes lead to apoptosis?
1. It will Cleave BID which will results cytochrome c to release from the mitochondria into the cytosol therefore the mitochondria aren’t able to produce ATP.
2. And it activated pro-caspase-3 which cleaves ICAD, which activates CAD
3. CAD travels to the nucleus where it degrades the DNA.
What is common to both pathways in which a cytotoxic T cell can kill?
What is the difference between initiator caspases and effector caspases in the apoptotic pathway?
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