CTSS and rheumatoid arthritis: CTSS activity in tears of male NOD mice, a murine model of SS, is greater than that in tears of healthy BALB/c mice4, while CTSS activity in tears of SS patients is greater than that in tears of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), non-autoimmune dry eye (DE) disorders, and healthy controls5.