pDC and B cell coculture
B cells were purified using B cell isolation kit II (130-091-151, Miltenyi Biotec) following the manufacturer’s protocol. B cells were activated with 5 μg/mL anti-IgM (314502, BioLegend), 500 ng/mL sCD40L (310-02, Peprotech), 100 ng/ml IL-4 (200-04, Peprotech), and 50 ng/ml IL21 (200-21, Peprotech). For pDCs and B cells coculture, purified CD19+ B cells (5×105/ml) and pDC from allogeneic HCs were added at the ratio of 10:1. The supernatants were harvested at day 7.