CD5 and B-cell chronic lymphocytic leukemia: The second most common disease observed in Dnmt3b+/− cohort was a CLL-like disease observed in three mice and characterized by splenomegaly and CD5+B220+CD19+ B-1a cells expansion of more than 20% in the blood, spleen, and bone marrow (Figs. 1A, 2, A–C, S1 and data not shown).