IMMUNOLOGICAL CLASSIFICATION OF CHRONIC MYELOID-LEUKEMIA DISTINGUISHES CHRONIC PHASE, IMMINENT BLASTIC TRANSFORMATION, AND ACUTE LYMPHOBLASTIC-LEUKEMIA

The clinical course of chronic myeloid leukemia (CML) is highly variab le and therefore it is difficult to predict the duration of the chroni c phase. We studied the immunological expression or maturation pattern s In 62 cases of CML (30 cases in clinical/cytological blast crisis (B C), 32 cases in clinical/cytological chronic phase (CP) by means of a double marker enzyme immune assay (DM-EIA). Immunological findings wer e supplemented by Southern blots using Ig-JH-, TCR beta- and bcr-probe s. Patients in BC (n = 30) expressed high proportions of CD10, CD20, C D33, CD34 and low degrees of a mature myeloid marker (CD15). Myeloid B C bone marrow (BM) cells showed a high degree of coexpression of unusu al, lineage restricted markers: 25% of CD15-positive cells also expres sed markers like CD10, CD20 or CD34. In contrast, BM cells in lymphoid BC did not show this coexpression. In CP two groups were distinguishe d immunologically: concordant cases which were immunologically normal (n = 14) and discordant cases (n = 18) which showed increased proporti ons of unusual, lineage restricted markers and double labelled cells ( e.g. CD15/CD34). The latter group developed clinical RC earlier during further follow up (p = 0.009). Cases of lymphoid BC (n = 11)-in contr ast to acute lymphoblastic leukemia (ALL) patients (n = 21)-did not sh ow coexpression of CD15/CD10, CD20, CD34. These data show that blast c lones can be detected in CML-CP by characteristic immunological matura tion defects several months before the clinical onset of BC. Moreover, the lymphoid ''blasts'' of CML-BC represent a relatively differentiat ed lymphoid population of cells which can be distinguished from ALL by their lack of to expression of unusual, lineage restricted markers.