We used two types of normal counterparts: CD19+ purified B cells from the peripheral blood of healthy volunteers (mean purity 97.9%, range 95.7–100) and CD19+ purified B cells from umbilical cord blood (mean purity 98.6, range 96.4–99.5), which are CD5+ (mean 88.6% ±1.5, range 80.9–97.6), similar to CLL B cells (mean 98.0% ±0.2, range 91–100) as discussed previously. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.