A novel in vitro model of early human adult B lymphopoiesis that allows proliferation of pro-B cells and differentiation to mature B lymphocytes

To develop a model of early human adult B lymphopoiesis, we cultured CD34(+)CD38(+)CD10(+) pro-B cells in contact with AFT024 stroma in X-VIVO10 media with 5% serum. The cytokines FLT3L + SCF + IL7 + IGF1 were added at day 0, IL4 + IL5 + IL6 + IL10 and soluble CD40 ligand at day 14, and Staph. aureus Cowan particles on day 21. Greater than 25-fold expansion of CD34(+)CD38(+)CD10(+) cells was seen at 2 weeks, the majority being CD34(-)CD19(+) pre-B cells. Differentiation to immature IgM(+) B cells was seen at 3 weeks and mature IgD(+) B cells at 4 weeks, with secretion of IgM into the media. Immature and mature B cells could also be generated from culture of CD34(+)CD10(+)CD19(-) and CD34(+)CD10(+)CD19(+) cells under similar conditions. In conclusion, we have demonstrated in vitro differentiation of early pro-B cells, and possibly common lymphoid progenitor cells, to mature B cells. Additional stimuli, provided by T helper cells or dendritic cells for example, may be required for the generation of IgG(+) B cells or plasma cells. However, our culture system should be a valuable tool to further investigate B cell biology and B cell malignancies such as multiple myeloma and lymphoma.