Eμ-TCL1A transgenic mice in which the TCL1A gene was under the control of a VH promoter-IgH-Eμ enhancer exhibited TCL1A expression enhancement in immature and mature B cells, serving as a model of human B chronic lymphocytic leukemia (B-CLL) physiopathology. This evidence concerns the gene TCL1A and B-cell chronic lymphocytic leukemia.