This disclosure provides IL-21 binding molecules, e.g., anti-IL-21 antibodies and antigen-binding fragments thereof. In certain aspects the anti-IL-21 antibodies and fragments thereof can be hybridoma-derived murine monoclonal antibodies, and humanized versions thereof. In certain aspects the binding molecules, e.g., anti-IL-21 antibodies and antigen-binding fragments thereof provided herein inhibit, suppress, or antagonize IL-21 activity. In addition, this disclosure provides compositions and methods for diagnosing and treating diseases or disorders, e.g., inflammatory, immune-mediated, or autoimmune diseases or disorders associated with IL-21-mediated signal transduction. In a particular embodiment, the disclosure provides methods for treating or preventing Graft-versus-host disease (GVHD) using IL-21 binding molecules, e.g., anti-IL-21 antibodies and antigen-binding fragments thereof.本發明提供IL-21結合分子，例如抗IL-21抗體及其抗原結合片段。在某些態樣中，抗IL-21抗體及其片段可為融合瘤源鼠類單株抗體，及其人類化型式。在某些態樣中，結合分子(例如本文所提供之抗IL-21抗體及其抗原結合片段)抑制、遏止或拮抗IL-21活性。另外，本發明提供用於診斷及治療疾病或病症(例如與IL-21介導之信號轉導有關的發炎性、免疫介導性或自體免疫疾病或病症)的組合物及方法。在一個特定實施例中，本發明提供使用IL-21結合分子(例如抗IL-21抗體及其抗原結合片段)治療或預防移植物抗宿主疾病(Graft-versus-host disease；GVHD)的方法。
