Molecular Mechanism of Sphingosine-1-Phosphate Receptor 1 Regulating CD4+ Tissue Memory in situ T Cells in Primary Sjogren's Syndrome

Our study suggests that the decrease of S1pr1 gene expression may provide a molecular basis for promoting the tissue retention and development of CD4+CD69+TRM cells.

Lymphocyte infiltration in labial salivary glands (LSG) of pSS patients was detected by H&E staining. Expression of sphingosine-1-phosphate receptor 1 (S1PR1) in LSG was examined by Immunohistochemistry. Immunofluorescence analyses were utilized to detect the co-expression of CD4, CD69 and S1PR1 in T cells of LSG of pSS patients. Expression of gene S1pr1 in peripheral blood CD4+T cells of healthy controls and pSS patients was detected by quantitative real-time PCR (QPCR). QPCR was used to examine the expression of gene S1pr1, Klf2, and Cd69 in the CD4+T cells that were co-cultured in vitro with cytokines TNF-α, TGF-β, and IL-33.

Although extensive research has been carried out on CD4+T cells infiltrating the labial glands in patients with primary Sjögren's Syndrome (pSS), it is still unclear how CD4+T cells remain in the labial gland tissue and develop into tissue resident cells. The aim of this study was to investigate the molecular mechanism by which CD4+T reside in labial glandular tissue of pSS patients.

S1PR1 was expressed in the infiltrating monocytes in LSG of pSS patients, and S1PR1 was weakly or even not expressed in cytoplasm of CD4+CD69+TRM cells of LSG in patients with pSS. Expression of gene S1pr1 in peripheral blood CD4+T cells of pSS patients was about three-fifths of that of healthy controls (P < 0.05). Expression of genes S1pr1 (P < 0.001) and Klf-2 (P < 0.001) was significantly decreased, and the expression of gene Cd69 (P < 0.05) was significantly increased in peripheral blood CD4+T cells of pSS patients co-cultured in vitro with cytokines TNF-α, TGF-β, and IL-33.