Expression of BAFF and APRIL in myeloma cells and normal plasmablasts. (A) Expression of BAFF and APRIL mRNA was analyzed by RT-PCR in 13 HMCLs, in CD138⁺ purified primary myeloma cells from 6 patients with intramedullary MM (patients 1-6), and 5 patients with plasma cell leukemia (patients 7-11), and in 5 normal in vitro–generated polyclonal plasmablastic cells (PPCs). B cells and dendritic cells (DCs) were used as negative and positive controls, respectively. (B) Cell-surface expression of BAFF was determined by flow cytometry using an anti-BAFF antibody. Broken lines indicate Ig control; and solid lines, anti-BAFF Ab.