FLOW CYTOMETRIC ASSAY FOR THE EVALUATION OF PHAGOCYTOSIS AND OXIDATIVE BURST OF POLYMORPHONUCLEAR LEUKOCYTES AND MONOCYTES IN MYELODYSPLASTIC DISORDERS

Background, Myelodysplastic syndromes are clonal diseases characterize d by pancytopenia of variable degree. Neutropenia is common and severa l. morphologic and functional abnormalities of polymorphonuclear neutr ophilic granulocytes (PMNs) and/or monocytes have been described. On t he basis of these observations, the phagocytic and oxygen intermediate s production of PMNs and monocytes was determined in a group of forty- seven patients affected by myelodysplastic syndromes of varying severi ty. Methods. A rapid, simple and reliable now cytometric method was de veloped to evaluate, in a one-step procedure, the phagocytosis rate an d the oxidative burst in PMNs and monocytes using a small amount of wh ole blood. Results. Phagocytosis of PMNs and monocytes was not signifi cantly reduced in refractory anemia (RA), while in refractory anemia w ith excess of blasts (RAEB) and in chronic myelomonocytic leukemia (CM ML) a clear decrease (p<0.05) of this function was found in both PMNs and monocytes. The production of oxygen intermediates by PMNs and mono cytes was significantly (p<0.01) reduced in RA as well as in RAEB and in CMML. Conclusions. This study indicates the presence in myelodyspla stic syndromes of a severe reduction in phagocytosis and oxygen interm ediates production (two crucial functions to protect the host against pyogenic agents) in both PMNs and monocytes. This observation could ex plain the severe morbidity and mortality from infections in patients a ffected by these hematological malignancies.