The population and properties of hematopoietic cells in Irf8−/− mouse bone marrow and spleen tissues are dramatically changed, along with development of chronic myelogenous leukemia and splenomegaly (Holtschke et al. 1996; Tamura et al. 2015; Tamura and Ozato 2002), thus it is difficult to clearly analyze the functions of Irf8 in monocytes/macrophages in the osteoclast precursor stage. Here, IRF8 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.