CTSS and Keratoconjunctivitis sicca: ,34–36 Because Sjögren syndrome and aged lacrimal glands share many similarities and activation of pathways related to immune activation,10 and because our work showed that 1-year-old Ctss−/− mice have less severe dry eye phenotype than aged wild-type controls,33 we hypothesized that a diet containing a cathepsin S inhibitor would also be beneficial during aging.