FIG. 3.

Inhibition of TNF-α-induced apoptosis by IL-27. (A) Leukemic cell lines were deprived of GM-CSF and cultured in serum-free assay medium containing 0.1% BSA in the absence or presence of 10 ng/mL TNF-α, 200 ng/mL IL-27, or 10 ng/mL TNF-α together with 200 ng/mL IL-27 for 4 h and 24 h. Following dual-staining with Annexin V-FITC and PI, percentages of apoptotic cells were determined by flow cytometric analysis of Annexin V+ cells. The Annexin V+ cells at early and late stages of apoptosis are shown as percentages in the lower right quadrant (Q4:% Annexin V+/PI−) and the upper right quadrant (Q2:% Annexin V+/PI+), respectively. Annexin V-FITC versus PI-PE plots with quadrant gates shown are representative of 3 independent experiments yielding very similar results. (B) OCI-AML5 and TF-1 cells were deprived of GM-CSF and cultured in serum-free assay medium containing 0.1% BSA in the absence or presence of 5 ng/mL TNF-α, IL-27 at indicated concentrations, or 5 ng/mL TNF-α together with IL-27 for 2.5 h. At the end of the treatment, the cells were lysed in Caspase-Glo 3/7 substrate and caspase-3/7 activities were assessed by the Caspase-Glo assay. *P < 0.05 for TNF-α plus IL-27 versus TNF-α alone.