Human leukemia has been determined and classified with the help of flow cytometry for the past two decades. Past attempts to detect leukemia blasts relied on both forward and side scatter (FSC and SSC) based on cell size and granularity. However, this technique failed to show a clean separation of blasts from normal lineage cells. In 1993, Borowitz, et al developed flow cytometric analysis to distinguish human leukemia blasts from other normal lineage cells by using fluorescence-conjugated CD45 antibodies (1). On CD45-SSC plots, the blasts are distinctly located below granuocytes in human acute myeloid leukemia. This technical advance has significantly improved diagnosis and classification of human leukemia.
Animal models mimicking human leukemia help us make a deeper understanding of leukemia progression and develop more effective therapeutic interventions in human leukemia. Recently, two groups of researchers published Bethesda proposals for classification of nonlymphoid and lymphoid hematopoietic neoplasms in mice (2,3). Similar to the French-American-British (FAB) criteria for human leukemia, the proposed classification depends on idenfication of leukemia blasts and their lineage identities. However, lack of a simple and sensitive methodology to identify leukemia blasts prevents us from characterizing leukemia in animal models and conducting subsequent translational research. Here we adopt the CD45-SSC analysis and characterize blasts and lineage cell populations of WT and Pten null T cell leukemia mice on CD45-SSC plots (4). The blast population is distinct from normal lineage cells, but its location is different from that of human blasts (4). The method is potentially useful for other murine leukemia models.