These IL‐10‐competent CLL cells also express cell surface phenotypes similar to nonmalignant B10 cells, indicating a functional relationship between CLL and B10 cells.18 We could not discriminate B10 cells and leukemic B cells in the aged miR‐15a/16−/− mice (15‐18 months) bearing B cell leukaemia. Here, IL10 is linked to B-cell chronic lymphocytic leukemia.