Anti-CD19-Fab-SEAm–directed lysis of 13 different B-cell lines. SAg concentration was 0.5 ng/mL and E:T ratio 40:1. Results are shown as specific cytotoxicity with the anti-CD19-Fab-SEAm fusion protein (minus cytotoxicity with C215-Fab-SEAm control fusion protein) as measured in a ⁵¹Cr-release assay. Each value is the mean of triplicate samples.