PROBLEM TO BE SOLVED: To provide antagonist antibodies useful for diagnosis and treatment of immune-related diseases (degenerative cartilaginous diseases such as rheumatoid arthritis or inflammatory diseases) with novel polypeptides having amino acid sequences similar to interleukin-17 (IL-17).SOLUTION: There is provided an antagonist antibody which binds, e.g., to an amino acid sequence encoded by the full-length coding sequence of the cDNA deposited under ATCC accession number PTA-1535.【課題】インターロイキン17(IL-17)にアミノ酸配列が類似した新規のポリペプチドで、免疫関連疾患(炎症疾患又はリウマチ様関節炎等の退行性軟骨性疾患)の診断及び治療にとって有用なアンタゴニスト抗体の提供。【解決手段】ATCC寄託番号PTA-1535で寄託されたcDNAの全長コード化配列によりコード化されるアミノ酸配列等に結合するアンタゴニスト抗体。【選択図】なし