The important of these concept is under scored by the experiments of Dougherty and Zinkernagel. Using virus-specific (virus 1) cytotoxic T cells. If antigen presenting cells (APC) of mouse A are mixed with T cells of mouse A in the context of virus 1 peptides, the T cell responds and kills the virus. If the MHC complex is from mouse B and the T cells are from mouse A, no killing occurs. Finally, if MHC and T cells are both from mouse A but virus 2 is unrelated to virus 1, no response will occur.