IL-2 from the microenvironment maintains Th2 cytokine-producing CD25⁺ CML LICs. (A) qPCR analysis of Th2 cytokine ligands and receptors in the indicated fractions from CML model mice (means ± SD, n = 4). (B) Serum cytokine levels in CML model mice and the control group were examined 11 days after transplantation (mean ± SD; CML, n = 6; GFP, n = 7). (C) Immunohistochemistry of bone marrow from CML model mice (white arrow: CD25⁺Lin⁻ LIC, orange arrowhead: Lin⁺IL-2⁺ cell). Blue: Lineage marker; green, GFP (ie, BCR-ABL⁺); magenta, CD25; white, IL-2. (D-E) BCR-ABL–transduced LSK cells were cultured in SF-O3 medium supplemented with 100 ng/mL TPO plus 100 ng/mL SCF; 100 ng/mL IL-2 or vehicle was added 4 days later. Cells were analyzed 16 days later. Representative profiles of the LSK fraction (D) and cell number (E) are shown as mean frequencies and cell numbers ± SD (n = 5). *P < .05; **P < .01.