Ontogeny of natural killer cells and T cells by analysis of BCR-ABL rearrangement from patients with chronic myelogenous leukaemia

Chronic myelogenous leukaemia (CML) is a haematological malignant disorder characterized by the Philadelphia chromosome (Ph) and BCR-ABL gene rearrang ement. This abnormal fusion gene can be considered to serve as a marker for the transformed cell clone in CML and is found in all cells arising from t he same malignant precursor cell. It has been detected in CML cells of the myeloid, monocytic, erythroid and B-lymphocytic lineages. However, it is st ill arguable as to whether T lymphocytes or natural killer (NK) cells carry this marker Answering this question would clarify the ontogenic relationsh ip between NE; cells and T cells. We examined 12 CML patients and studied t he expression of BCR-ABL rearrangement by fluorescence in situ hybridizatio n (FISH) in both NK cells and T cells sorted by flow cytometry. The purity of T cells was 95.6-99.8% and that of NK cells was 95.3-99.3% after sorting . Neither NK cells nor T cells showed any positive BCR-ABL signal with the exception of one patient who recovered from a lymphoid blastic crisis. We s peculate that T cells and NK cells originate from BCR-ABL-negative stem cel ls.