Overexpression of BCL6 and Bcl-xL confer a high proliferative capacity and fixed differentiation phenotype to peripheral blood CD27+IgG+ memory B cells (a) Flow cytometry identification of BCL6-transduced (ΔNGFR+), Bcl-xL-transduced (GFP+) and BCL6+Bcl-xL transduced (GFP+ΔNGFR+) CD19+ B cells in culture with CD40L-L cells and IL-21 four days post transduction. (b) Percentages of the individually transduced populations over time within a single non-sorted culture maintained with CD40L-L cells and IL-21. BCL6+Bcl-xL ○, Bcl-xL-only ■, BCL6-only □ transduced cells or non-transduced cells (●). (c) Cultured double-transduced cells were left unsorted (left panel) or the individual populations were sorted (right panel) and cultured separately. The cumulative cell number was calculated based on the original number of transduced B cells at input and illustrates the theoretical absolute cell numbers produced in culture. (d) CD19+ cells from non-sorted double transduced cultures were analyzed for CD38, HLA-DR, and surface Ig kappa (IgL-κ) or lambda (IgL-λ) light chain expression. The gates in the upper panel show the percentage terminally differentiated cells. Phenotype shown of cells 7 days post transduction. Data are representative of four separate experiments.