It is intended to provide a closed culture system of virus-specific CTL which has convenience and safety features and can be implemented at low cost for the purpose of achieving the practical application of cell therapy with the use of CTL specific to a virus (particularly HCMV). After virus-specific CTL epitope peptide and peripheral blood mononuclear cells are mixed and incubated, restimulation with this epitope peptide is given in a medium. Then, virus-specific CTL is isolated by targeting freshly expressed CD137 antigen, and T cells proliferated from peripheral blood mononuclear cells by the stimulation with OKT3 (anti-CD3 monoclonal antibody) are brought into contact with the epitope peptide in the medium. Then, the T cells and the virus-specific CTL are cocultured, whereby the virus-specific CTL is proliferated.
