Reduction in CD4⁺ T-cell dose in early DLI is correlated with increased engraftment of LSCs. (A) Survival curve of B10.D2→Balb/c recipients of BCR-ABL1–transduced BM treated with early DLI with the indicated dose of purified CD4⁺ splenocytes (n = 5 for each cohort). As controls, recipients received either no DLI (no splenocytes, solid line) or DLI with unfractionated splenocytes at the standard dose (1.5 × 10⁷ splenocytes). (B) Southern blot analysis of leukemia-initiating cell frequency in genomic DNA of BM from the cohorts in panel A. The blot was hybridized with a GFP probe (top panel) to quantify the number of engrafting LSCs or with an ABL1 probe (bottom panels) to quantify proviral DNA content, as in Figure 1C. Note that recipients of 4 × 10⁶ T cells had only 1-2 clones per leukemic recipient. The band indicated by the asterisk is a background band. (C) Quantification of frequency of engrafting LSCs from the data shown in panel B. The difference in number of engrafting LSCs between untreated recipients and recipients of 4 × 10⁶ CD4⁺ splenocytes was significant (P = .0002, unpaired t test).