Chapter 21: Activation of Cytotoxic T Cells - 4 functions of cytokines

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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?


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