On the other hand, aging Tet2-KO mice expand clonal CD19+B220low immunoglobulin (Ig)M+ B-cell subpopulations, which are transplantable and display similarities to chronic lymphocytic leukemia (CLL), including sensitivity to ibrutinib-induced B-cell receptor signaling blockage24. Here, CD19 is linked to B-cell chronic lymphocytic leukemia.