Fig. 1

Functional characteristics and cathepsin S in different biocompartments. Primary Sjögren syndrome (pSS) patients showed significantly reduced ocular tear production (a) and reduced spontaneous or stimulated salivary flow, when compared to healthy controls (HC) (b). CatS (activity/conc) ratios were significantly elevated for tears of pSS when compared to HC, whereas no significant increase could be observed for the other biocompartments (c). By contrast, ratios for CatL, an endopeptidase involved in collagen and elastin degradation during necrotic and tumorous processes, were significantly decreased in tears of pSS as when compared to HC (d) (Mann-Whitney U test, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). An inverse association between tear (e) and saliva (f) production and CatS ratios in pSS individuals is suggesting a CatS-dependent inflammatory process as causative for the decreased exocrine function (Spearman’s rank correlation, one-tailed t test, respectively)