The present invention generally relates to antibodies, antigen-binding fragments thereof, polypeptides, and immunoconjugates that bind to CD123 antigen (the α chain of the interleukine 3 receptor, or IL-3R α). The present invention also relates to methods of using such CD123-binding molecules for diagnosing and treating diseases, such as B-cell malignancies.本發明大體上係關於結合CD123抗原(介白素-3受體之α鏈或IL-3R α)之抗體、其抗原結合片段、多肽及免疫結合物。本發明亦係關於使用此種CD123結合分子來診斷及治療諸如B細胞惡性病之疾病的方法。