Cytolytic activity of resting PBL containing approximately 10% NK cells against the CD30⁺ cell line L540CY at different effector:target ratios in a 5-hour JAM-test assay. The diabody (•) was used at concentration of 1 μg/mL and the biMoAb (▴) at a concentration of 4 μg/mL. Thus, approximately 1.5× more biMoAb than diabody was used when calculated on a molar basis. The diabody (1 μg/mL) without PBL (○) and PBL alone (□) were used as negative controls.