1,25-dihydroxyvitamin D3 regulates t helper and b lymphocyte responses substantially in drug-naive primary Sjögren’s syndrome patients’ mononuclear cells

Abstract

Background/aim: A correlation between vitamin D deficiency and primary Sjögren’s syndrome (pSS) has already been described. The limited data has been reported regarding the pathological relevance of vitamin D in primary Sjögren’s syndrome. In this study, the peripheral blood mononuclear cells were cocultured with 1,25-dihydroxyvitamin D3 to determine the modulatory effect of vitamin D3 on T and B lymphocyte phenotypes in pSS. Materials and methods: Venous blood samples were collected from 11 patients in the treatment phase and 9 drug-naive pSS patients. Peripheral blood mononuclear cells (PBMC) were isolated and separately cultured in the presence and absence of 1,25- dihydroxyvitamin D3 (10 mM) for 5 days of culture period. Lymphocyte proliferation was analyzed for CFSE signaling via flow cytometry. CD3+CD4+ cells were analyzed for intracellular IFN- and IL-17 expressions. CD19+IgD cells were analyzed for CD38 and CD27 expressions to evaluate naive and total memory B cell subsets. Culture supernatants were analyzed for the IFN-, IL-17, and IL10 cytokine secretions via flow cytometry. Results: 1,25-dihydroxyvitamin D3 significantly decreased Th lymphocyte proliferative responses in drug-naive (p < 0.005) and treated pSS patients (p < 0.05), and B lymphocyte proliferation in drug-naive pSS PBMC cultures (p < 0.01) compared to mononuclear cell cultures alone. 1,25-dihydroxyvitamin D3 significantly decreased IFN- and IL-17 secreting Th cells in both drug naive (p < 0.005 and p < 0.01, respectively) and treated subjects (p < 0.05 and p < 0.05, respectively) by increasing FoxP3 expressing CD4+CD25+ Treg cell frequency. Plasma B lymphocytes significantly reduced in the presence of 1,25-dihydroxyvitamin D3 in drug naive pSS (p < 0.001) and treated patients (p < 0.05) mononuclear cell cultures compared to PBMC cultures alone. Total memory B cell subsets significantly increased with 1,25-dihydroxyvitamin D3 in drug naive pSS when compared with PBMC cultures alone (p < 0.005). IFN- and IL-17 cytokine levels in culture supernatants significantly reduced (p < 0.05 and p < 0.01, respectively) in drug naive pSS patients’ PBMC cultures with 1,25-dihydroxyvitamin D3, and IL-10 levels significantly enhanced in both drug-naive (p < 0.01) and treated pSS patients’ PBMC cultures (p < 0.01) in the presence of 1,25-dihydroxyvitamin D3. Conclusion: In conclusion, 1,25-dihydroxyvitamin D3 regulated immune responses in both treated and drug-naive pSS patients, but have a more pronounced modulatory effect on mononuclear cell responses in drug-naive pSS patients.Key words: Primary Sjögren’s syndrome, 1,25-dihydroxyvitamin D3, immunomodulation