FIGURE 6.

Effects of apoptotic targets on BU.MPT responder cell viability are recognition-dependent but independent of phagocytosis. Serum-starved BU.MPT responder cells were exposed to apoptotic (Apo) targets at a target/responder cell ratio of 10:1 for 2 h, as depicted in the inset, in either the absence (Control) or the presence of cytochalasin D (Cytochalasin), an inhibitor of phagocytosis. The source of apoptotic targets was DO11.10 cells treated with actinomycin D (Act D), staurosporine (Stauro), or dexamethasone (Dex). After 24 h, relative cell number by MTT assay (A) or [³H]thymidine incorporation (B) was determined. All values were normalized against those for BU.MPT responder cells not exposed to targets. Each data point in the graphs represents the mean and S.E. from a minimum of three separate experiments. Absolute A_570/650 values (A) and cpm (B) for responder cells unexposed to targets in the absence of cytochalasin D were 0.344 ± 0.012 and 2972 ± 173, respectively. All experimental A_570/650 values (A) and cpm (B) were normalized to these values as represented by the dotted lines at relative cell number (A) and relative thymidine incorporation (B) equal to 1.0. A, p < 0.0001, apoptotic targets versus no targets in the presence and absence of cytochalasin D. B, p < 0.0001, apoptotic targets versus no targets in the presence and absence of cytochalasin D. Error bars (A and B) denote S.E.