TLX1 and acute lymphoblastic leukemia: Based on those findings, we used fluorescence-activated cell sorting (FACS) to isolate the following ALL-SIL populations: cells with shRNA-mediated knockdown of TLX1 were sorted for a CD1bLowCD55High surface phenotype (predicted "low" TLX1), and control vector-transduced cells were sorted into CD55High (predicted intermediate or "medium" TLX1) and CD55Low (predicted "high" TLX1) populations.