Efficient In Vitro Plasma Cell Differentiation by B Cell Receptor Activation and Cytokine Stimulation.

Plasma cells (PCs) constitute a small proportion of B cells, limiting their biochemical characterization. An in vitro culture system that reliably generates PCs could provide an alternative method to obtain PCs for further analysis and manipulation. To date, most in vitro PC differentiation methods rely on B cell receptor (BCR)-independent stimulants, including TLR ligands, CD40L, and cytokines. However, these methods do not fully recapitulate the natural T cell-dependent PC differentiation process, in which BCR activation is the initial events. In this study, we established an efficient in vitro PC differentiation method incorporating BCR stimulation. Naïve B cells were first stimulated with anti-IgM and anti-CD40 Abs, followed by stimulation with various cytokines. By screening cytokines known to participate in PC differentiation in vivo, we identified that the combination of IL-4 and IL-5 induced the most efficient PC differentiation. The in vitro generated PCs highly expressed PC-associated surface markers and regulatory genes. Additionally, they secreted high amounts of IgM and IgG Abs. Moreover, retroviral transduction of B cells resulted in efficient target gene expression in PCs. Our new method closely mimics natural PC differentiation and effectively generates a large quantity of PCs for various applications, including elucidating the molecular mechanisms underlying PC differentiation.