Fig. 5.

Inhibition of Ex3 diabody activity (6-h ⁵¹Cr release assay) by parental or irrelevant mAb IgGs. The TFK-1 cells were co-cultured with T-LAK cells at an E:T ratio of 20 in the presence of Ex3 diabody (1.0 μg/ml) in combination with parental IgG (closed triangle 528; closed square OKT3) or irrelevant IgG (open triangle, MUSE11; open square OKT8) at various concentrations (0.1–10.0 μg/ml). Cytotoxic activity of T-LAK cells against TFK-1 in the absence of Ex3 diabody is also shown (+): ## p<0.01 for cytotoxic activity of T-LAK cells with vs without Ex3 diabody. *** p<0.001 and **** p<0.0001 for percentage of specific lysis of T-LAK induced by Ex3 diabody (1.0 μg/ml) in the presence of parental IgG vs in the absence of parental IgG. The E:T ratio was 20. Data are representative of four independent experiments, using T-LAK cells from different donors, with similar results