Figure 5.

Blocking analysis of the anti‐human CD19 immunotoxins for the human CD19 receptor on human CD19⁺ JeKo‐1 lymphoma cells. Unlabeled anti‐human CD19 immunotoxins were each incubated with JeKo‐1 cells at a range of concentrations for 15 min at 4 °C in the dark. Subsequently, without washing the cells, anti‐human CD19 mAb (FMC63) was added to each tube containing cells in the presence of the unlabeled immunotoxins. Binding affinity of the anti‐human CD19 immunotoxins to the human CD19 receptor on JeKo‐1 cells was measured by a decrease in anti‐human CD19 mAb staining in the presence of increasing concentrations of the unlabeled immunotoxins.