Changes

**Perforins are structurally related to complement factor C9

**Perforins are structurally related to complement factor C9

**Granzymes are proteolytic enzymes that target cell nucleases and cause apoptosis  

**Granzymes are proteolytic enzymes that target cell nucleases and cause apoptosis  

In both cases direct contact is required between the T cell and target cell, and cell killing can take several minutes.</p><p> Cytotoxic T cells secrete a pattern of cytokines similar to that of TH1 cells i.e. IFN-γ but not IL-2. IFN-γ shifts the balance of the immune response in favour of TH1 cells giving an increased level of T cell proliferation. The initiation of the immune response via cytotoxic T cells leads to the selective proliferation of cytotoxic T cells enhancing the main mechanism of killing infected cells.</p>

In both cases direct contact is required between the T cell and target cell, and cell killing can take several minutes.</p><p> Cytotoxic T cells secrete a pattern of cytokines similar to that of TH1 cells i.e. IFN-γ but not IL-2. IFN-γ shifts the balance of the immune response in favour of TH₁ cells giving an increased level of T cell proliferation. The initiation of the immune response via cytotoxic T cells leads to the selective proliferation of cytotoxic T cells enhancing the main mechanism of killing infected cells.</p>

==γδ cells==

==γδ cells==