Comparison of CD22-CAR and CD19-CAR–mediated lysis. (A) ⁵¹Cr-release assay to evaluate lytic activity of CD22 HA22SH-28z second-generation CAR (inverted triangle), m971-28z second-generation CAR (gray triangle), CD19 CAR (squares), or mock transduced T cells (circles) against ALL lines, as listed. The E/T ratio is shown on the x-axis. (B) Top row, flow cytometric analysis of CD22 expression on 7 primary patient pre-B ALL samples (see “Methods”). Percentage expression over control is indicated. Bottom row, lysis of patient blasts with m971-28z or HASH-28z–expressing T cells in a 4 hours ⁵¹Cr-release assay, percent lysis indicated at E/T ratio of 30:1. Significant differences between the vectors is noted (average of triplicate wells). For m971 versus mock, P5 and P7 had P > .05, for HASH P2, P5, and P7 has P > .05, all other values versus mock were less than 0.05.