JAK inhibition elevates MHC-II expression in CML stem/progenitor cells. (A) Quantitative RT-PCR of RNA/cDNA generated from either non-CML or CML stem/progenitor samples for IL-4 transcripts revealed higher expression levels of IL-4 in CML cells. Data are expressed relative to the reference gene HPRT1. Primary (B) CD34⁺CD38⁺ CML cells and (C) CD34⁺CD38⁻ CML LSCs were treated with IFN-γ and/or JAK inhibitor (RUX, 200 nM), as indicated. The average MHC-II expression levels were determined by flow cytometry, normalized to CML UT sample. NS, not significant. (D) Representative histograms showing MHC-II expression on CD34⁺CD38⁺ and CD34⁺CD38⁻ CML cells treated with IFN-γ and/or RUX, as indicated; Primary CD34⁺ CML stem/progenitor cells were treated with IFN-γ and/or RUX, as indicated earlier. Thereafter, 300 cells were sorted for either (E) CD34⁺CD38⁺ CML and (F) CD34⁺CD38⁻ CML LSC populations, and the average gene expression of CIITA was determined by quantitative reverse transcription polymerase chain reaction (n = 6 for CD34⁺CD38⁺, n = 3 for LSC; calibrated to UT CML sample). Statistical significance was calculated between UT CML sample and all other samples and, if significant, is indicated by asterisks above the bars.