The present invention relates to TR21 polypeptides. In particular, isolated nucleic acid molecules are provided encoding human TR21 protein. TR21 polypeptides are also provided as are vectors, host cells and recombinant methods for producing the same. The invention further relates to screening methods for identifying agonists and antagonists of TR21 activity. The invention further relates to the treatment, diagnosis, or prognosis of autoimmune diseases or disorders including Sjogren's syndrome using TR21 polynucleotides, polypeptides, agonists or antagonists.