Table 1.
Comparison of concentrations of the 4KB-PE40 IT, PE or the scFv alone inhibiting protein synthesis by 50% of control values (IC 50 )
| Daudi | Ramos | HSB-2 | H9 | |
|---|---|---|---|---|
| IC 50 | ||||
| IT | 7 nM | 4 nM | >300 nM | >300 nM |
| PE | 200-300 nM | >750 nM | 60 nM | >750 nM |
| scFV | >3200 nM | >3200 nM | >3200 nM | >3200 nM |
CD22+ cell lines Daudi and Ramos or CD22− lines HSB-2 and H9 were exposed for 48 h to the 4KB scFv-derived immunotoxin (IT) or to native PE exotoxin A (PE) or 4KB antibody fragment alone (scFv) and cytotoxicity was evaluated by protein synthesis inhibition assay as described in the Methods section.