We show here that the elevated activity of CTSS found in LG lysates and tears of SS-model male NOD mice may be partially due to decreases in Cys C. These findings were extended to a clinical population, with the demonstration that tears of SS patients exhibit a similar imbalance between CTSS and Cys C, and suggesting that reduced levels of Cys C as well as possibly deficiencies in additional endogenous protease inhibitors may contribute to increased tear CTSS activity. Here, CTSS is linked to synovial sarcoma.