Stability of RFB4(dsFv)PE38. RBF4(dsFv)PE38 was incubated at 37°C for the number of days indicated and cytotoxicity on CA46 cells was compared with a sample that was stored at −80°C. (○), 7 days; (▵), 5 days; (•), 3 days; (▴), 1 day; (▪), 0 days.