L428 and KM-H2 CD20⁺ cell populations exhibit high ALDH activity and clonogenic potential. (A) ALDH activity for the CD30⁺ and CD20⁺ subsets. The data represent the mean ± SEM of the MFI difference between Aldefluor-stained cells with and without DEAB from 8 separate experiments. (B) The initial plating of 500 ALDH^high L428 cells produced 19.7 (± 9.5) colonies compared with 5.7 ± 11 colonies from 500 ALDH^low L428 cells (P = .3), and 500 ALDH^high KM-H2 cells generated 33.3 ± 5.4 colonies compared with 20.7 ± 6.4 from 500 ALDH^low KM-H2 cells (P = .3). Upon secondary replating, the original 500 ALDH^high L428 generated 251 ± 25.9 colonies compared with 53.6 + 12.9 from the ALDH^low L428 cells (P = .01), and the original 500 ALDH^high KM-H2 cells produced 243.7 ± 32.3 colonies compared with 27.7 ± 16 ALDH^low KM-H2 cells (P = .03). The data represent the mean ± SEM of 3 separate experiments.