Diagram 4 A killer T-cell does not lock into an MHC antigen
(self) without a viral antigen. But when a viral antigen binds
to an MHC antigen, the shape of the MHC antigen is altered
and a matching receptor on a killer T-cell can recognise the
viral-MHC antigen complex (altered self). When a T-cell
receptor locks into a viral-MHC antigen complex, the killer
T-cell releases molecules that penetrate the infected cell
and kill it. This shuts down the virus factory. Receptors on
killer T-cells are unique because they are specific for both
the viral antigen and the MHC antigen.