[Enhancement of tumor-specific killer T cell activities by high-dose methotrexate]

High-dose methotrexate (100 mg/kg) and citrovorum factor rescue enhanced syngeneic sarcoma (S1509a) specific killer T cell (cytotoxic T lymphocyte) in tumor bearing mice, although high-dose MTX suppressed killer T cell against S1509a in immunized mice. It was suggested that tumor specific suppressor T lymphocyte played an important role in enhancement of killer T cell. Enhancement of killer T cell was induced at day seven after administration of MTX. From the clinical point of view, weekly high-dose (100 mg/kg) MTX therapy may be necessary to enhance tumor specific immunity of the patients with sarcoma. High-dose MTX therapy is a unique one not only in practical point of view, but also in immunological point of view.