CD33 and acute promyelocytic leukemia: Yet, when we analyzed the amount of APL blast cells (defined by CD117+CD33+) versus myeloid committed cells (CD117-CD33+CD11b+) in the GFP+ fraction, we observed a ratio (APL blasts: myeloid committed) of 1:2 in MLL5 transplanted mice compared to 3:1 in control mice.