Expression of the major transcription factors involved in the in vitro differentiation of B cells into plasmablastic cells.

RT-PCR for BSAP/Pax-5, PRDI-BF1, IRF-4, and XBP-1 were performed on purified PB B cells (B, lanes 1 and 2), on purified plasma cells from a patient with reactive plasmacytosis (RP, lane 3), and on CD20⁻/CD38⁺⁺ sorted polyclonal plasmablastic cells (PPC, lanes 4-6).