Chapter 21: Activation of Cytotoxic T Cells - 4 functions of cytokines
Activated by exposure to antigens on MHC 1 proteins presented by infected cells or APC's (dendritic cells)
How are CD8 cells activated (cytotoxic T cells)?
Activated by binding to antigen fragments presented by MHC II molecules on the surface of APC's
How are Helper T cells activated?
Helper T cells release cytokines like interleukin 2, causing dendriticc cells to express co-stimulatory molecules required for CD8 cell activation
How does Co-stimulation work?
Can take up to 2 days from time of first exposure to antigen for cystic T cells to reach effective levels
How long can it take for Cytotoxic T cells to reach their effective levels?
Stimulate T cell divisions (produce memory T cells and acerbate cytotoxic T cell maturation) - attract and stimulate macrophages - attract and stimulate NK cells - promote activation of B cells
What are the 4 functions of Cytokines?
Divide into active helper T cells (secrete cytokines) and memory T cells (remain in reserve)
What do Acitvated CD4 T cells divide into?
Absence of costimulation results in T cell inactivation
What does an absence of co-stimulation result in?
For T cell to be fully activated, it must be costimulated by binding to stimulating cell at second site
What is Costimulation?
Also called killer T cells - seek out and immediately destroy target cells
What is another name for cytotoxic T cells/what is their function?
Induce apoptosis (cell suicide)
What is the function of Granzymes?
Stay in circulation - Immediately form cytotoxic T cells if same antigen appears again
What is the function of Memory Tc Cells?
Secrete suppression factors - limit immune reaction to single stimulus
What is the function of Suppressor T cells?
Perforins form pores to allow granzymes access to the cytoplasm
What is the function of perforin?
CD4 proteins assit in the process of activating helper T cells
What proteins assist in activating helper T cells?
After initial immune response (slower than Tc cells)
When does suppressor T cells secrete supression factors?
To destroy target cell
Why does Cytotoxic T cells secrete poisonous lymphotoxin?
Prevent autoimmune reactions
Wat do suppressor T cells prevent?
Produced with cytotoxic T cells
What are Memory Tc Cells produced with?
Inhibitory cytokines, such as IL 10 and TGF beta
What are examples of suppression factors secreted by suppressor T cells?
Release perforin and granzyme - secrete poisonous lymphotoxin - bind to specific membrane receptor that induces apoptosis in target cells
What are the 3 actions of Cytotoxic T cells?
