抗原特異的細胞傷害性T細胞(CTL)は抗腫瘍免疫療法において重要な役割を担っている。微量残存CML細胞を根絶するため，imatinib療法を４年間受けたCML症例にWT1ペプチドワクチンを投与した。混合リンパ球ペプチド培養(MLPC)を行い，WT1/MHC-tetramer+CD8+細胞の出現頻度の評価によって末梢血中のWT1特異的CTLの増幅効果の推移を確認した。その結果，WT1ペプチドワクチン投与を終了し６年経過した現在も，WT1特異的CTL はCD8陽性細胞中5-15x10^<-6>の頻度で検出され続けていることが確認された。CTLの検出の検討に加えて，長期間増幅されたWT1特異的CTLのT細胞受容体β鎖可変領域(TCRVβ)のレパトワを８回の解析を試みた。MLPC後，CD8+T細胞中のWT1特異的CTLの割合が高いwellについてレパトワ解析を行った。WT1ペプチドワクチンやMLPCには単一の9merのペプチドを使用したが，３種類のTCRVβの使用が見られた。imatinibとWT1ペプチドワクチン併用療法はCML症例においてWT1特異的CTLを長期間持続させる点で有効であることが確認された。さらに，本研究では，WT1特異的CTLにおいてはoligoclonalなTCRVβが使用されている可能性が示唆された。Antigen specific cytotoxic T lymphocytes (CTLs) play an important role in cancer immunotherapy. To eradicate tumor cells, we administrated WT1 peptide vaccine for a CML patient who was being treated imatinib therapy. The appearance of WT1 specific CTLs in peripheral blood was confirmed by evaluating the frequency of MHC/WT1 tetramer+CD8+ T cells by using mixed lymphocyte peptide culture (MLPC) system. After the cessation of vaccination, WT1 specific CTLs remained at the level of 5-15x10^<-6> in CD8+ T cells, which is lasting thereafter for 6 years. These cells showed cytotoxicity against WT1 peptide with MHC classⅠ restricted. In order to identification of T cell receptor β-chain variable region (TCRVβ) in CML patient received WT1 peptide vaccine, We also investigated the usage of T CVβof WT1 specific CTLs. MLPC cells with high proportion of CD8+ WT1 tetramer+ T cells were assessed for TCRVβ usage by using TCRVβ gene family specific monoclonal antibodies and flow cytometry. Cells from each well cultured by MLPC showed various types of TCRVβ repertoires from well to well. WT1 peptide vaccination for an imatinib pretreated CML patient is effective in terms of longterm generation of WT1 specific CTLs with cytotoxicity against WT1 peptide. The present study suggested that CTLs detected by MLPC possessed oligoclonal features of TCRVβ gene used, but not identical. Taken together, CTLs induced by tumor antigen specific peptide are potent for antitumor immunity.