A method for treating an organ for transplantation or a method for suppressing a transplanted immune response, comprising storing an organ for transplantation in the presence of an anti-T cell antibody in the preservation solution and then washing off the preservation solution before transplantation.移植用臓器を、保存液中抗T細胞抗体の存在下で保存した後、移植前に当該保存液を洗い流すことを特徴とする、移植用臓器の処理方法、又は移植免疫応答の抑制方法。