Development of CD8+ T cells in the thymus

Raine Toivonen

Double negative T cell

Lymphoidprogenitor

Double positive T cell

Cortical epithelialcell

Death byNeglect due toWeak signalling

CORTEXMEDULLA

CD8 committed T cell

CD4 committed T cell

THYMUS

Medullary epithelial cellOr

Dendritic cell

CD8 T cell

Negative selectionand death

Positiveselection

TO THEPERIPHERY!

Activation of CD8+ T cells in the periphery

Raine Toivonen

CD8+ T CELL

AgTCR

CD28

IL-2IL-2

IL2R

IL2R

CD8

Dendritic cell

MHC I

CD80 / CD86

• CD8+ T cell encounters an activated APC

• The APC presents antigen on its surface within MHC I

• Antigens can be bound to MHC I either when they are synthesized within the cell (endogenous or viral antigens) or transferred from phagosomes to cytosolic compartment (cross-presentation of exogenous antigens)

• CD8 T cell produces IL-2 to drive its own proliferation

The DC is activated by CD4+ T cell: license to kill

Raine Toivonen

CD8+ T CELL

AgTCR

CD8

IL12R

DENDRITIC CELL

MHC I Ag TCRCD4

CD28B7(CD80 / CD86)

CD4+ T HELPER CELL

CD40LCD40

CD28

Killing mechanisms1. Perforin/Granzymes

Raine Toivonen

Ag

CTL Infected cell

CASPASE

DNA

DISC

Killing mechanisms

Raine Toivonen

2. FAS / FAS ligand

Ag

CTL Infected cell

CASPASE 3

CASPASE 2

DAXXDAXX RIP1RIP1RAIDDRAIDD

APOPTOSIS

ASK1

JNKJNK

FAD

DFA

DD

ProCASPASE 8

CASPASE 8