Changes

===Activation Scenarios===

===Activation Scenarios===

#'''No signal 1''':

1. '''No signal 1''':

*T cell is not activated as there is no antigen.

:T cell is not activated as there is no antigen.

#'''Both signal 1 and signal 2'''

2. '''Both signal 1 and signal 2'''

*T cell is activated into clonal expansion and produces cytokines or becomes cytotoxic.  

:T cell is activated into clonal expansion and produces cytokines or becomes cytotoxic.  

#'''Signal 1 but no signal 2'''

3. '''Signal 1 but no signal 2'''

* T-cell is triggered into apoptosis and dies.  

:T-cell is triggered into apoptosis and dies.  

* This is the basis of "clonal deletion" and is a major mechanism of the development of tolerance.  

:This is the basis of "clonal deletion" and is a major mechanism of the development of tolerance. It ensures that T-cells do not react with self (non-dangerous) antigens.

It ensures that T-cells do not react with self (non-dangerous) antigens.

===TCR Complex===

===TCR Complex===