pDCs did not contribute to peripheral and affected tissue type I IFN signature in pSS patients
To determine whether pDC from pSS patients displays the enhanced capacity of IFN-α secretion, we stimulated freshly isolated PBMCs with TLR7 (R848) or TLR9 ligand (ODN-2216) and determined representative cytokines production by flow cytometry. However, upon stimulation, there was no difference in the IFN-α secretion of pDCs between HC and pSS patients (Fig 2a-b). The same was observed in the IL-6 and TNF-α production (Fig 2c-f).
We next detected the infiltration of pDCs in labial glands by immunofluorescence to explore whether they contribute to tissue type I IFN signature in pSS patients. Only one patient had a few pDCs infiltration, while the other three hardly had any pDCs in the labial gland (Fig 3a). Recent researches highlighted the role of salivary epithelial cells in producing type I IFNs [27-29], consistently, our immunofluorescent results indicated that epithelial cells are responsible for the production of tissular IFN-α in patients with or without pDC infiltration (Fig 3b). We also detected the main chemokine receptors, including CCR2, CCR4, CCR5, CCR7, and CCR10 on the pDC surface showed no difference between pSS patients and HCs (Fig 3c, Fig S2j).