1. ¹Servicio General de Citometría and Departamento de Medicina, Centro de Investigación del Cáncer (Instituto de Biología Molecular y Celular del Cáncer; CSIC-USAL), Universidad de Salamanca, Salamanca, Spain
2. ²Servicio de Hematología, Hospital Universitario de Salamanca, Salamanca, Spain
3. ³Servicio de Hematologia, Hospital Miguel Servet, Zaragoza, Spain
4. ⁴Servicio de Hematologia, Hospital de Alcañiz, Teruel, Spain

Correspondence: Professor A Orfao, Servicio General de Citometría and Departamento de Medicina, Centro de Investigación del Cáncer (Instituto de Biología Molecular y Celular del Cáncer; CSIC-USAL), Campus Miguel de Unamuno, 37007-Salamanca, Spain. E-mail: orfao@usal.es

Received 29 October 2007; Revised 31 January 2008; Accepted 7 February 2008; Published online 13 March 2008.

Abstract

Occurrence of phenotypic abnormalities in CD34⁺ hematopoietic progenitor and precursor cells (HPC) and their major B-cell and nonlymphoid compartments has been frequently reported in myelodysplastic syndromes (MDS). Here, we analyze for the first time the numerical and phenotypic abnormalities of different maturation-associated subsets of bone marrow (BM) CD34⁺ HPC from 50 newly diagnosed MDS patients in comparison to normal/reactive BM (n=29). Our results confirm the existence of heterogeneously altered phenotypes among CD34⁺ HPC from MDS and indicate that such variability depends both on the relative distribution of the different subsets of CD34⁺ HPC committed into the different myeloid and B-lymphoid compartments, and their immunophenotype (for example, higher reactivity for CD117 and CD13 and lower expression of CyMPO, CD64 and CD65 on CD34⁺ immature and neutrophil precursors), a clear association existing between the accumulation of CD34⁺ HPC and that of immature CD34⁺ HPC. Interestingly, expansion of erythroid- and neutrophil-lineage CD34⁺ cells is detected in low-grade MDS at the expense of CD34⁺ plasmacytoid dendritic cell and B-cell precursors, while expansion of immature CD34⁺ precursors occurs in high-grade MDS. On the basis of the number and severity of the phenotypic abnormalities detected, a scoring system is proposed that efficiently discriminates between normal/reactive and MDS CD34⁺ HPC, the mean score significantly increasing from low- to high-grade MDS.