Expression profiling of terminal B cell differentiation [RNA-Seq]

The terminal differentiation of B cells into antibody-secreting cells (ASCs) is a critical component of adaptive immune responses. Using our in vitro differentiation system, we combined RNA sequencing with ATAC-seq to characterize genomic events driving the ASC differentiation of human primary naive B cells. After an initial response to IL-4, cells that committed to an ASC fate downregulated the CD23 marker and IL-4 signaling, whereas cells that maintained IL-4 signaling did not differentiate. As demonstrated in the mouse, downregulation of the human ubiquitin ligase CBLB was required to free IRF4 from proteasomal degradation and produce levels needed for ASC differentiation. Our results evidenced two previously undocumented mechanisms driving human terminal B cell differentiation. Lastly, we showed that CD23-negative cells (i) carried the imprint of their previous activated B-cell status, (ii) were precursors of plasmablasts, and (iii) had a similar phenotype to in vivo pre-plasmablasts. Overall design: Four cell populations of in vitro differentiating B cells were analyzed by RNA-seq in triplicates.