sCD27 induces APRIL and CD40L on WM patient BM MCs. Expression of APRIL (A) and CD40 ligand (B) on CD70-expressing LAD2 MCs, and primary BM MCs from 10 patients with WM following stimulation with sCD27 (10 μg/mL) alone (shaded histogram) or sCD27 (10 μg/mL) after preincubation with the CD70-directed SGN-70 (1 μg/mL) mAb (clear histogram, solid line). Dotted, clear histograms denotes isotype control.