(A) Extracellular (top panel) and intracellular (bottom panel) expression of Fas-L. Anti-CD3 (1 μg/well) and/or anti-CD2 (5 μg/well) MoAbs were allowed to adhere in 96-well flat-bottomed plates. 3DO cells were cultured for 20 hours on coated plates and then stained with either anti–Fas-L Ab against the extracellular portion or anti–Fas-L Ab against the intracellular portion of the molecule, as described in the Materials and Methods. The number in the upper right corner represents the percentage of cells expressing Fas-L (top panel) or the value of the histogram median (bottom panel). (B) Fas-L expression as evaluated by the cytotoxicity assay (see the Materials and Methods) with 3DO cells untreated or treated with anti-CD3 (1 μg/well) and/or anti-CD2 (5 μg/well) for 20 hours. The results represent the average of three experiments (each in triplicate culture). *P < .01 comparing anti-CD3 + anti-CD2–treated versus anti-CD3–treated group. E:T ratio, 25:1.