Both CD4⁺ and CD4^- splenocytes can mediate GvL against CML-like leukemia. Cumulative mortality due to leukemia (A), and overall survival (B), of nonchimeric mice with BCR-ABL–induced CML-like leukemia (purple, n = 2), of leukemic mixed chimeras without DLI (blue, n = 4), or chimeras treated with DLI in form of unfractionated splenocytes (red, n = 7), CD4⁺ splenocytes (yellow, n = 8) or CD4^- splenocytes (green, n = 7). The frequency of fatal CML in chimeras treated with CD4⁺ splenocytes was significantly lower than in untreated chimeras (P = .05, Fisher exact test). One mouse in the CD4^- DLI cohort died at day 28 of a mixture of CML-like disease and GvHD, and another succumbed to histiocytic sarcoma at day 100 (see text).