Elevated IgM levels in the presence of BLyS. CD19⁺CD138⁺ cells (0.25 × 10⁶ cells/well) from WM patients (n = 5) were cultured in 48-well plates in the presence of 100 ng/mL BLyS, cytokines (20 U/mL IL-2, 5 ng/mL IL-6, 5 ng/mL IL-10, and 2 ng/mL IL-12), a combination of BLyS + cytokines, or media alone. One week following treatment, supernatants were harvested and used to test for IgM secretion using ELISA. Results for 5 WM patients are presented as means ± standard deviation (SD) of duplicate wells.