Changes

==Cytotoxic T-Cells==

==Cytotoxic T-Cells==

Cytotoxic T cells kill virus infected cells where the organisms are contained in the cell cytoplasm. Viruses are obligate intracellular pathogens that use the host cell machinery for pathogen protein synthesis; viral peptides associate with MHC class I and are expressed on the cell surface. [[Lymphocytes#Cytotoxic CD8+|CD8+ cytotoxic T-lymphocytes (CTL)]] recognise the antigen-MHC complex.

Cytotoxic T cells kill virus infected cells where the organisms are contained in the cell cytoplasm. Viruses are obligate intracellular pathogens that use the host cell machinery for pathogen protein synthesis; viral peptides associate with MHC class I and are expressed on the cell surface. [[T_cells#Cytotoxic_CD8.2B|CD8+ cytotoxic T lymphocytes (CTL)]] recognise the antigen-MHC complex. Cytotoxic T-cells secrete a pattern of cytokines similar to that of TH₁ cells:

* Cytotoxic T-cells secrete a pattern of cytokines similar to that of TH₁ cells.

*IFNγ but not IL-2. The IFN&gamma shifts the balance of the immune response in favour of TH₁ cells and there is therefore an increased level of T-cell proliferation. The initiation of the immune response via CTL leads to the selective proliferation of CTL which enhances the main mechanism of killing virally-infected cells.  

** I.e. IFNγ but not IL-2.

*** The IFNγ shifts the balance of the immune response in favour of TH₁ cells.

**** There is therefore an increased level of [[T cells|T-cell]] proliferation.  

***** The initiation of the immune response via CTL leads to the selective proliferation of CTL - enhances the main mechanism of killing of virally-infected cells.  

===Killing Mechanism===

===Killing Mechanism===