Cytofluorometric profiles for 3 representative MCCs.

Shown are profiles for cell proliferation (A) and cytoplasmic IL-6 production (B). Cells were incubated in culture medium or the presence of 100 ng/mL anti–IL-6 mAb. Myeloma cell proliferation was evaluated by BrdU-PI cell incorporation. IL-6⁺ MCC-2 and MCC-3 (B) showed high percentages of spontaneous BrdU⁺ cells (A). Addition of anti–IL-6 mAb inhibited proliferation of MCC-2 and MCC-3, but had no effect on IL-6⁻ MCC-4.