Recombinant OPN inhibits AICD but not Fas-induced cell death. T cells were grown for 6 days in the presence (▪) and absence (□) of rOPN. Then, Fas-induced cell death was triggered using a soluble anti-Fas mAb (CH11), whereas AICD was induced by incubating cells in wells coated with an anti-CD3 mAb (OKT3). The rOPN (500 ng/mL) was added in the assays involving the rOPN-grown cells. Cell survival was assessed after 18 hours. Results are expressed as relative survival percentage (ie, the proportion of surviving cells relative to the corresponding control, untreated or treated with rOPN). Results are the means ± SD of 5 experiments each performed in duplicate. The P value was calculated using the Mann-Whitney U test. Similar results were obtained in 2 experiments in which apoptotic cells were detected by propidium iodide and annexin V staining (data not shown).