Monocyte depletion severely attenuates IFN-γ secretion by PBMCs stimulated with Herceptin-coated tumor cells and IL-12. (a) A whole PBMC population (PBMC; 12% CD14+ cells), a monocyte-depleted PBMC population (Mono-depleted; < 0.1% CD14+ cells), and a pure monocyte population (not shown; 95% CD14+ cells) were cultured with the SKBR3 cell line in our in vitro coculture assay with either 10 ng/ml rhuIL-12 or rhuIL-2. Standard controls were also included. (b) The monocyte-depleted population was “replenished” with various amounts (percent of original) of pure monocytes. Culture supernatants were harvested at 72 hours and analyzed for IFN-γ content. *P < 0.05 versus medium, Herceptin, IL-12, IL-2, Herceptin + IL-2, and Herceptin + IL-12 (monocyte-depleted).