After gating out CD3+ T and CD11b+ myeloid populations, cells were visualized using CD19 and CD5 expression markers: a phenotypically homogeneous CD19+/CD5+ co-expression population (CLL-like cells) with marked expansion in the blood was observed in Eμ-MTCP1 mice but not wildtype littermates. This evidence concerns the gene CD19 and B-cell chronic lymphocytic leukemia.