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===Killing Mechanism===
 
===Killing Mechanism===
 
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The CTl killing mechanism is initiated by direct CTL-target cell contact.   
* The CTl killing mechanism is initiated by direct CTL-target cell contact.   
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* The cells involved bind by antigen/[[MHC]] class I-TcR interaction. This allows the CTL's intracellular granules to be localised at the area of contact - the granules contain most of the molecules responsible for cytotoxicity.  
* The cells involved bind by antigen/[[MHC]] class I-TcR interaction.
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* Direct cell contact stimulates the release of the granule contents into the area of contact between the two cells. The granules contain two groups of cytotoxic molecules.
** This results in the CTL's intracellular granules becoming localised to the area of contact.
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#Perforin, which is structurally related to the [[Complement|complement]] component, C9 and forms pores in the cell membrane.
*** These granules contain most of the molecules responsible for cytotoxicity.  
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#Granzymes, which are proteolytic enzymes that target cell nucleases and cause programmed cell death.
* Direct cell contact stimulates the release of the granule contents into the area of contact between the two cells.  
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* The granules contain two groups of cytotoxic molecules.
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** Perforin.
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*** Structurally related to the [[Complement|complement]] component, C9.
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*** Forms pores in the cell membrane.
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** Granzymes.
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*** Proteolytic enzymes.
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*** Target cell nucleases.
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*** Cause programmed cell death.
      
==T-Cell Activation==
 
==T-Cell Activation==
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