PBMC Isolation and In vitro stimulation
Human PBMCs were isolated with Ficoll-Paque density (DAKEWE, China) as previously described[8]. For the plasma stimulation, PBMCs from HCs were seeded into 24-well plates at a density of 1×106/ml and maintained in RPMI 1640 (Gibco, A10491, USA) with 20% mixed plasma from ten pSS or HCs in the presence of 100 ng/ml IL-3 for 4 hours.
For IgG and IgA stimulation, freshly isolated PBMCs from HCs were first incubated with 100 mg/ml IL-3 for 2 hours, then stimulated with human IgG (SP001, Solarbio) and human IgA (SP016, Solarbio) with indicated concentrations. IL3 is used to assist the survival of pDCs in vitro [24, 25].