The present invention relates to a novel CK.alpha.-5 protein which is a member of the alpha chemokine family. In particular, isolated nucleic acid molecules are provided encoding the human CK.alpha.-5 protein. CK.alpha.-5 polypeptides are also provided, as are vectors, host cells and recombinant methods for producing the same. Antibodies and fragments thereof that specifically bind to CK.alpha.-5 polypeptides are also disclosed, as are compositions and methods for making such antibodies. The invention further relates to screening methods for identifying agonists and antagonists of CK.alpha.-5 activity. Also provided are diagnostic methods for detecting immune system-related disorders and therapeutic methods for treating immune system-related disorders.