Combinatorial activation of WM B cells by TLR7 agonist, BCR triggering, and T-cell help generates PCs. (A) B cells derived from the peripheral blood of 2 healthy donors (left panel) or 2 WM patients (middle and right panels) were stimulated with CD40L+anti-BCR (CD40L), CD40L+R848+anti-BCR (CD40L+R848), or R848+anti-BCR (R848). The fold change in cell number at each time point was determined by manual counts for day 3 and day 6 and then by flow cytometry thereafter. The cell number at each point was normalized to the number of “input” cells for that specific patient obtained at day 0. The immunophenotype of cells from a representative healthy (B) or WM (C) sample, stimulated as in panel A, was assayed by flow cytometry at each time point. Percentages are displayed for each quadrant.