M1-MØ and M2-MØ secretion of cytotoxic factors and cross-activation in coculture with MM cells. (A-B) MM cell death was analyzed after 72 hours of coculture of MM cells alone or in the presence of various types of the indicated MØ, in cell-cell contact experiments (A) and non–cell-cell contact Transwell experiments (B). (C-D) Determination by enzyme-linked immunosorbent assay of TNF-α (C) and IL-12 p40 (D) levels in supernatants collected after 48 hours of culture of various types of the indicated MØ, MM cell lines, or MM+MØ cocultures. (E) NCI-H929 and U266 cells were cultured with TNF-α (200 ng/mL) or supernatants collected from GM-MØ+NCI-H929 and GM-MØ+U266 cocultures, respectively (measured in C), and treated with infliximab (80 μg/mL), as indicated. GM-MØ+MM conditioned media were inactivated by heat (10 minutes at 100°C). (F) Conditioned media of various types of the indicated MØ were collected and added to NCI-H929 or U266 cells (50% vol/vol). MM cell death was measured after 72 hours of culture. Summarized results of at least 3 independent experiments with different donors ± SEM are shown. *P < .05; **P < .01; ***P < .001.