PBMC-OCs protected MM cells from apoptosis. MM cells were cultured in alpha-MEM containing 1% FBS in the presence or absence of PBMC-OCs (1 × 10⁴/mL). Primary MM cells, OPC cells, and U266 cells were harvested after gently pipetting at the indicated time points (A). RPMI8226 cells were harvested sequentially (B). Annexin V–FITC and PI binding was measured by flow cytometry. Intact cells are located in the lower left quadrant of dot plots.