The present invention relates to nucleic acid molecules encoding Neutrokine-alpha and/or Neutrokine-alphaSV polypeptides, including soluble forms of the extracellular domain. Neutrokine-alpha and/or Neutrokine-alphaSV polypeptides are also provided as are vectors, host cells and recombinant methods for producing the same. The invention further relates to antibodies or portions thereof that specifically bind Neutrokine-alpha and/or Neutrokine-alphaSV and diagnostic and therapeutic methods using these antibodies. Also provided are diagnostic methods for detecting immune system-related disorders and therapeutic methods for treating immune system-related disorders using the compositions of the invention.
