To differentiate between the newly secreted endogenous MIF and the potential MIF present in the media from cancer cells, BM macrophages engulfing apoptotic RM1 (efferocytic) from three independent BM macrophage co-cultures were sorted by flow cytometry (double positive F4/80-FITC+/RM1(a)-DeepRed+) and compared to F4/80+ non-engulfing BM macrophages (non-efferocytic, also sorted by flow cytometry) (Figure 3F). Here, MIF is linked to cancer.