Cell-Mediated Immunity (involves the destruction of infected or abnormal cells via the clonal selection of a cytotoxic T cell)

Cytotoxic cells (type of T lymphocyte)

key plays of cell-mediated immunity

the assess the MHC Class 1 marker of infected cells

• MHC Class 1 markers can display antigens that have been broken down in a cell on its surface, meaning MHC Class 1 markers on a cell that has been infected with a virus can present foreign viral antigens

1. 
   

at the same time as the selection of T helper cells, APCs come upon a naive T cell that has a T cell receptor which matches the antigen being presented, initiating clonal selection

the naive T cell become selected, and is stimulated by cytokines released by the selected T helper cell to undergo clonal expansion and differentiate into cytotoxic T cells and T memory cells

2. 
   

• cytotoxic T cells leave the lymph node and travel throughout the body to reach the site of infection

• T memory cells stay in the body for extended periods of time and provide immunological memory

3. 
   

Due to clonal selection, the cytotoxic T cells that arrive at the site of infection all have T cell receptors that are specific to the foreign antigen that was selected for 

once the cytotoxic T cell has found an abnormal cell that is presenting complementary foreign antigens on its MHC Class 1 complex, it binds to it and releases chemicals to induce apoptosis