OBL inhibition by MM marrow plasma is reversed by anti-IL-3 neutralizing antibody in patients with high IL-3 and unaffected in patients with normal IL-3 in CFU-F cultures. BM stromal-cell cultures were treated with BM plasma from patients with high IL-3 (more than 50 pg/mL; MM1) or normal IL-3 (less than 5 pg/mL; MM2) without (▪) or with (▧) anti-IL-3 mAb (1 μg/mL). After 14 days of culture, ALP staining was performed and quantified by 1D Image Analysis Software (Kodak Digital Science). Data represent the average ± standard deviation of 3 wells for each condition for a typical experiment.