ACTIN POLYMERIZATION IN NEUTROPHILS FROM PATIENTS AFFECTED BY MYELODYSPLASTIC SYNDROMES - A FLOW CYTOMETRIC STUDY

In this study F-actin polymerization in neutrophils from 21 patients a ffected by myelodysplastic syndromes (MDS) was evaluated by means of a flow cytometric assay. Neutrophils were stimulated with formyl-methio nyl-leucyl-phenylanaline (fMLP; 10(-8) M final concentration) for 15, 30, 60 and 120 sec, and F-actin content was determined using fluoresce in-isothiocyanate phallacidin as a specific probe. Eight normal subjec ts were studied as controls. We found that F-actin polymerization was defective in ten patients, with very impaired values after 60 and 120 sec of stimulation with fMLP. The remaining 11 patients showed a preva lent neutrophil population with normal F-actin polymerization and neut rophil sub-populations with either defective or undetectable F-actin p olymerization. In the first group, patients with very poor prognosis ( refractory anemia with excess blasts, refractory anemia with excess bl asts in leukemic transformation, trisomy 8, multiple karyotypic abnorm alities) were present, although patients with aberrations of karyotype were present in the second group. It is possible that defects in neut rophil F-actin polymerization may be responsible for neutrophil dysfun ction, which has frequently been observed in MDS. (C) 1997 Elsevier Sc ience Ltd.