CD25⁺ LICs and CD25⁻ LICs interconvert, and CD25⁺ LICs maintain CD25⁻ LICs. (A) CD25⁺F⁻LSK or CD25⁻F⁻LSK cells from CML model mice (3 × 10³ cells per sample) were cultured for 8 days. (B-C) Representative profiles (B) and calculated cell number (C; mean ± SD) are shown (n = 4). (D-E) BCR-ABL–transduced CD25⁺LSK or CD25⁻LSK cells (7.5 × 10³ per sample) were transplanted into recipient mice, and splenic cells were analyzed 11 days later. Representative profiles of the LSK fraction (D) and cell numbers (E) are shown as mean frequencies and cell numbers ± SD (CD25⁺LSK, n = 4; CD25⁻LSK, n = 11). (F) Design of coculture study. Ly5.2⁺CD25⁺F⁻LSK cells alone, a mixture of Ly5.2⁺CD25⁺F⁻LSK cells and Ly5.1⁺CD25⁻F⁻LSK cells, and Ly5.1⁺CD25⁻F⁻LSK cells alone (3 × 10³ of each cell type) were cultured for 8 days. (G) Cell number in CD25⁻F⁻LSK-derived fractions without or with CD25⁺F⁻LSK cells in panel F (means ± SD, n = 4). (H-I) LSK cells in GFP⁺Ly5.1⁺ cells were analyzed (means ± SD, n = 4); representative profiles (H), and the frequency of CD25⁻ or CD25⁺ LSK cells (I) are shown. *P < .05; **P < .01.