Thymic stromal lymphopoietin expression from benign lymphoproliferation to malignant B-cell lymphoma in primary Sjögren's syndrome

To investigate the expression of thymic stromal lymphopoietin (TSLP) in primary Sjögren's syndrome (pSS), stratified according to the lymphoproliferative status, from a fully benign (fbSS) stage to myoepithelial sialadenitis (MESA) and to B-cell non-Hodgkin's lymphoma (NHL). After initial serum studies in large numbers of pSS patients and in controls, TSLP was investigated also in pathologic salivary glands (SG) biopsies from 38 stratified pSS patients (13 fbSS; 13 MESA; 12 NHL) and from 13 controls with non-autoimmune sicca syndrome (nSS) by RT-PCR, immunohistochemistry and immunofluorescence. Significantly higher TSLP serum levels were shown in pSS than controls, increasing from fbSS to MESA and to NHL. In SG biopsies, TSLP-positive B lymphocytes increased with increasing lymphoproliferation, maximally in NHL, consistent with the detection of inducible TSLP long isoform (lfTSLP) mRNA only in MESA and NHL. By contrast, the constitutive TSLP short isoform (sfTSLP) mRNA showed no difference among subgroups. The TSLP expression by glandular epithelium declined with the progression from fbSS to MESA and to NHL. TSLP progressively increases from benign to malignant B-cell lymphoproliferation in pSS. The salivary epithelium expresses TSLP but, with the progression of lymphoproliferation, the B-cells may represent the major source of TSLP, in its long inducible isoform. A possible pathogenetic role of TSLP is herein hypothesised in pSS for the first time. Further analyses on TSLP, also as a biomarker of pSS and related lymphoproliferation, are worthwhile.