Correspondence To

the editor: Detection of genetic markers on different populations of hematopoietic progenitor cells in B-cell chronic lymphocytic leukemia B-cell chronic lymphocytic leukemia (B-CLL) results from the clonal expansion of CD51/CD231 B-lymphocytes. The malignant transformation is assumed to occur at the level of mature B lymphocytes. Newer studies, however, have questioned this assump-tion. Estrov et al were able to generate CLL B-lymphoid colonies in vitro from CD341 progenitor cells.1 Gahn et al have detected genetic abnormalities, such as trisomy 12 and Rb1 deletions, at the level of CD341 progenitor cells,2 and Faguet et al have found granulocytes and monocytes expressing common CLL antigen in a large subset of B-CLL patients.3 In order to further explore this important issue, we studied different cell populations for the presence of certain genetic abnormalities, such as deletions o