The frequency and phenotype analysis of peripheral pDC in pSS patients
We first analyzed the frequency of pDC in PBMCs from treatment-naïve pSS (n=31), HCQ-treated pSS (n=17), SLE (n=9), and HCs (n=29) by flow cytometry. The demographic characteristics of all the included pSS patients were demonstrated in Supplementary Table 2 and SLE patients were demonstrated in Supplementary Table 3. The gating strategy of pDCs was shown in Figure S1a. In accordance with previous studies [20, 26], the percentage of pDCs was significantly lower in PBMCs from treatment naïve SLE and pSS patients compared with HCs. Interestingly, the reduction of pDCs rebounded in pSS patients after Hydroxychloroquine (HCQ) therapy (Fig 1a). However, we did not observe the hyperactivation status of pDCs in pSS as the activation markers CD80, CD83, and CD86 expressions were equal to HCs (Fig 1b, Fig S1c).
Detection of TLR7/9 expressions showed that unstimulated pDCs from pSS patients showed higher TLR7 but not TLR9 expressions compared with HCs (Fig 1c, d). However, the difference vanished after TLR7 (R848) or TLR9 ligand (ODN2216) stimulation (Fig 1e, f).