Validation of thymic stromal lymphopoietin as a biomarker of primary Sjögren's syndrome and related lymphoproliferation: results in independent cohorts

OBJECTIVES: Thymic stromal lymphopoietin (TSLP) has been implicated in primary Sjögren's syndrome (pSS) and related B-cell lymphoproliferation and lymphoma (NHL) by studies on salivary pathologic tissues and serum. The purpose of this work was to validate serum TSLP as biomarker of pSS and related lymphoproliferation by the study of two additional independent cohorts. METHODS: Serum TSLP was measured by ELISA in the original published Cohort-1 from Udine, Italy, including 91 patients. Two additional cohorts were then studied for validation: Cohort-2, including 4 sub-cohorts comprising 125 patients from the Universities of Roma, L'Aquila, Pisa and Perugia, belonging to the Italian SS Study Group (GRISS), and Cohort-3, including 59 patients from the University of Athens, Greece. Overall, 159 control subjects were enrolled. Active pSS-NHL, as well as pre-lymphomatous conditions, i.e. persistent salivary gland swelling and mixed cryoglobulinaemia, were investigated in detail. In addition, serum samples from pSS-NHL in complete remission were analysed (n=27). RESULTS: TSLP serum levels were confirmed to be significantly higher in pSS compared to controls in both Cohort-2 and Cohort-3, in particular in patients with lymphoproliferation. Serum TSLP was much higher in pSS pre-lymphomatous conditions. Finally, active NHL showed the highest TSLP serum levels, while in NHL in remission TSLP resulted undetectable or significantly lower than in benign pSS. CONCLUSIONS: By the study of independent cohorts, it was again demonstrated that serum TSLP levels are increased in pSS, above all in more advanced B-cell lymphoproliferation and NHL. Serum TSLP can therefore represent a novel biomarker for pSS-related lymphoproliferation.