The present invention is directed to polynucleotides encoding polypeptides associated with the development of rheumatoid arthritis and homologs thereof. The invention further relates to diagnostic and therapeutic methods for utilizing these polynucleotides and polypeptides in the diagnosis, treatment, and/or prevention of rheumatoid arthritis and related disease states. The invention further relates to screening methods for identifying agonists and antagonists of the polynucleotides and polypeptides of the present invention, and compounds identified thereby.