Assessment of P-CrKL in CD34⁺ and CD34⁺CD38^– CML cells using a novel intracellular flow cytometry method. P-CrKL status was measured by this intracellular FACS technique using a P-CrKL primary antibody and FITC-conjugated secondary antibody. These experiments confirmed significantly increased P-CrKL in the primitive CD34⁺CD38^– subpopulation compared with total CD34⁺ cells (P = .002). MFI indicates mean fluorescence intensity.