Importantly, SS patients exhibit higher IFN-γ levels and enhanced Th1 activity in salivary glands compared to non-SS sicca patients [19,20], implying that the presence of l-KYN in the serum can be used as a marker to distinguish between autoimmune-mediated sicca (i.e., SS) and non-SS sicca. The gene discussed is IFNG; the disease is synovial sarcoma.