WHICH COMPARTMENTS ARE INVOLVED IN PHILADELPHIA-CHROMOSOME-POSITIVE CHRONIC MYELOID-LEUKEMIA - AN ANSWER AT THE SINGLE-CELL LEVEL BY COMBINING MAY-GRUNWALD-GIEMSA STAINING AND FLUORESCENCE IN-SITU HYBRIDIZATION TECHNIQUES

Chronic myeloid leukaemia (CML) is believed to represent a stem cell d isorder involving all three cell lineages. The typical chromosomal abe rration, the Philadelphia chromosome, is the translocation (9;22)(q34; q11). Several studies with cytogenetics, fluorescence ill situ hybridi zation (FISH), or polymerase chain reaction have investigated the pres ence of the t(9;22) in different cell compartments. However, questions still remain. In six cases of CML we combined the standard May-Grunwa ld-Giemsa staining with FISH at the single-cell level and were able to demonstrate that not only all maturation stages of granulopoiesis, er ythropoiesis, and megakaryocytes, but also plasma cells, eosinophils, basophils and monocytes carried the Philadelphia chromosome in 53-98% of samples. Using immunological identification of single cells we were able to demonstrate that the t(9;22) is detectable in 34% of CD3-posi tive T lymphocytes, in 32% of CD19-positive B lymphocytes, and in 82% of CD34-positive precursor cells, The results give new insight into th e biology of CML, and may have implications for future therapeutic str ategies.