Late apoptotic cells induce the same signaling events as do early apoptotic cells
A, serum-starved BM macrophages were pre-exposed to increasing numbers of late apoptotic (Apo) BUMPT cells for 30 min and then stimulated with M-CSF for 15 min. Late apoptotic cells were added to macrophages at a cell to macrophage ratio ranging from 1:64 to 1:1 in 2-fold increments. B, serum-starved BM macrophages were pre-exposed to mixtures of apoptotic and necrotic (Nec) BUMPT cells for 30 min. The number of necrotic cells was kept constant at a necrotic cell to macrophage ratio of 1:1, and the number of apoptotic cells was increased as shown. Nonadherent cells were removed by rinsing, and macrophage lysates were probed with anti-active ERK1/2, p38, JNK, and p90Rsk antibodies. Equal loading was confirmed by Ponceau S staining of blotted proteins as well as probing for total ERK1/2, p38, JNK, or p90RSK (supplemental Fig. S5, except for total JNK, which is not shown). Apoptotic and necrotic cells alone contributed no active ERK1/2, p38, JNK, or p90Rsk in these experiments.