CCL5 induces IL-6 secretion. (A) HS-5 (0.01 × 10⁶ cells/well), Saka and stromal cells generated from WM patients (WMsc1-WMsc4; 0.1 × 10⁶ cells/well) were serum starved overnight and then cultured in the presence or absence of 500 ng/mL Rantes/CCL5 for 24 hours and IL-6 levels were determined in the culture supernatant by ELISA. (B) IL-6 secretion in coculture wells of stromal cells (0.1 × 10⁶ cells/well) and BCWM.1 or CD19⁺CD138⁺ cells from WM patients (0.5 × 10⁶ cells/well). Cells were serum starved overnight and then cocultured for 2 days, then supernatants were harvested and used to quantitate IL-6 levels by ELISA. (C) IgM secretion in coculture wells of HS-5 stromal cells or WMsc (P1 and P2; 0.1 × 10⁶ cells/well) and BCWM.1 (0.5 × 10⁶ cells/well) or (D) HS-5 cells cocultured with CD19⁺CD138⁺ cells from WM patients (P1 and P2). Cells were serum starved overnight and then cocultured for 2 days then supernatants were harvested and used to quantitate IgM levels by ELISA.