Specificity of lysis of WT1-positive tumor cells is demonstrated by cold target inhibition.

Bars represent the mean percentage of specific lysis and standard deviations in chromium release assays performed in triplicate with E:T ratios of 25:1, 5:1, and 1:1. (A) Cytotoxic activity of the p117-139 specific T-cell line against the WT1-negative cell line EL-4 (EL-4, WT1-negative); the WT1-positive tumor cell line TRAMP-C (TRAMP-C, WT1-positive); TRAMP-C cells incubated with a 10-fold excess (compared to the hot target) of EL-4 cells pulsed with the relevant peptide p117-139 (TRAMP-C + p117-139 cold target) without ⁵¹Cr labeling and TRAMP-C cells incubated with EL-4 pulsed with an irrelevant peptide without ⁵¹Cr labeling (TRAMP-C + irrelevant cold target). (B) Cytotoxic activity of the p117-139–specific T-cell line against the WT1-negative cell line EL-4 (EL-4, WT1 negative); the WT1-positive tumor cell line BLKSV40 (BLKSV40, WT1 positive); BLKSV40 cells incubated with the relevant cold target (BLKSV40 + p117-139 cold target), and BLKSV40 cells incubated with the irrelevant cold target (BLKSV40 + irrelevant cold target).