Explain the mechanism of cell mediated immunity.

The immunity mediated by the T-cells, natural killer cells etc., is known as cell mediated immunity.

• Exogenous antigens are processed and displayed by MHC-II of antigen presenting cells. They are recognised by T_H cells and release interleukins.
• Endogenous antigens are processed by altered self-cells and are displayed on their membranes by MHC-I and recognised by T_C cells.
• Interleukins transform T_C cell into cytotoxic lymphocyte (CTL).
• CTLs release perforins and granzymes and destruct the infected cells and cancer cells.