HA22-LR is resistant to digestion with lysosomal extracts. HA22 and HA22-LR were incubated with lysosomal extracts of Raji cells under identical conditions. After the addition of lysosomal extract, samples were removed immediately (0), after 30 minutes, and after 1, 2, 4, 8, and 24 hours, then analyzed by reducing SDS-PAGE. Arrows indicate the V_L, V_H-PE38 (HA22), and V_H-PE25 (HA22-LR) bands that comprise the mature immunotoxins.