IRF8 and neoplasm: Flow-cytometric analysis supported increased Notch1 protein expression but decreased Ikaros and IRF8 protein expression by DN2a and DN2b cells isolated from tumor-bearing IL-10−/− mice (Figures 5B2,B3, Supplementary Figure 1), suggesting a pivotal role of IL-10 in the reciprocal regulation of Notch1 and Ikaros signaling, leading to the arrest of T-cell maturation at the DN2 stage.