The present invention is directed to a novel naturally occurring human cytokine that is comprised of a heterodimer of interleukin-17 and interleukin-17F designated herein as interleukin 17A/F (IL-17A/F). Also provided herein are vectors and host cells comprising those nucleic acid sequences, chimeric polypeptide molecules comprising the polypeptides of the present invention fused to heterologous polypeptide sequences, specific antibodies which bind to the polypeptides of the present invention and to methods for producing the polypeptides of the present invention. Further provided herein are methods for treating degenerative cartilaginous disorders and other inflammatory diseases.本發明係針對一種新穎的、天然產生之人類細胞激素,其包含本文中命名為介白素17A/F(IL-17A/F)之介白素-17與介白素-17F之異源二聚體。本發明亦提供包含彼等核酸序列之載體及宿主細胞、包含與異源多肽序列融合之本發明之多肽的嵌合多肽分子、與本發明之多肽結合之特異性抗體,及用於產生本發明之多肽之方法。本發明進一步提供用於治療退化性軟骨病症及其他發炎疾病之方法。