Apoptotic cells inhibit whereas necrotic cells activate ERK1/2 in bone marrow-derived macrophages
Serum-starved BM-derived macrophages were stimulated with increasing numbers of apoptotic cells, necrotic cells, or latex beads alone for 15 min (A) or stimulated with M-CSF for 15 min following a 30-min pre-exposure to apoptotic cells, necrotic cells, or latex beads (B). Apoptotic or necrotic BUMPT cells were added to macrophages at a cell to macrophage ratio ranging from 1:64 to 1:1 in 2-fold increments, as indicated by the schematic diagram of increasing cell ratio. Nonadherent cells were removed by rinsing, and macrophage lysates were probed with anti-active ERK1/2 antibody. Equal loading was confirmed by Ponceau S staining of blotted proteins as well as probing for total ERK1/2 (supplemental Fig. S1). Apoptotic and necrotic cells alone contributed no active ERK1/2 in these experiments.