CD19 and B-cell chronic lymphocytic leukemia: Once signs of disease occurred, we harvested splenocytes of the TCL1tg AKT1E17K Mb1-CreERT2 mice and confirmed CLL development by detecting a pronounced CD19+CD5+ CLL cell population in the spleen that did not express the AKT1 transgene, as indicated by the GFP-negative CLL/B-cell population (Fig. 1d).