PROBLEM TO BE SOLVED: To provide a method for detecting DNA damage in a cell by specifically recognizing a molecule responsive to DNA chain cleavage.SOLUTION: According to the present invention, there is provided an antibody that specifically reacts with human Ly6D, the antibody comprising: specific amino acid sequences as a heavy chain first complementarity-determining region (VH CDR1), a heavy chain second complementarity-determining region (VH CDR2), and a heavy chain third complementarity-determining region (VH CDR3), which are found by: obtaining a phage antibody (scFv antibody) that reacts with an antigen, which is expressed responsive to the cleavage of DNA double strand on a cell membrane by phage display technology using a human antibody library； and analyzing the gene sequence thereof. The antibody is selected from peptides comprising Fab, Fab', F(ab), single chain antibody (scFv), dimerized V region (Diabody), disulfide stabilized V region (dsFv) or CDR.SELECTED DRAWING: None【課題】DNA鎖切断応答性分子を特異的に認識することによる細胞におけるDNA損傷の検出方法の提供。【解決手段】ヒト抗体ライブラリーファージＤｉｓｐｌａｙ技術により細胞膜上にあるDNA二本鎖切断応答的に発現する抗原と反応するファージ抗体（ｓｃＦｖ抗体）を取得し、その遺伝子配列の解析により見出された、重鎖第１相補性決定領域（ＶＨ ＣＤＲ１）、重鎖第２相補性決定領域（ＶＨ ＣＤＲ２）及び重鎖第３相補性決定領域（ＶＨ ＣＤＲ３）として夫々特定のアミノ酸配列を有する、ヒトLy6Dと特異的に反応する抗体。抗体が、Ｆａｂ、Ｆａｂ’、Ｆ（ａｂ）２、一本鎖抗体（ｓｃＦｖ）、二量体化Ｖ領域（Ｄｉａｂｏｄｙ）、ジスルフィド安定化Ｖ領域（ｄｓＦｖ）又はＣＤＲを含むペプチドから選ばれる抗体。【選択図】なし
