Flow cytometric assay for the evaluation of phagocytosis and oxidative burst of polymorphonuclear leukocytes and monocytes in myelodysplastic disorders

Istituto di Medicina Clinica, University of Trieste, Italy.

BACKGROUND. Myelodysplastic syndromes are clonal diseases characterized by pancytopenia of variable degree. Neutropenia is common and several morphologic and functional abnormalities of polymorphonuclear neutrophilic granulocytes (PMNs) and/or monocytes have been described. On the basis of these observations, the phagocytic and oxygen intermediates production of PMNs and monocytes was determined in a group of forty-seven patients affected by myelodysplastic syndromes of varying severity. METHODS. A rapid, simple and reliable flow cytometric method was developed to evaluate, in a one-step procedure, the phagocytosis rate and the oxidative burst in PMNs and monocytes using a small amount of whole blood. RESULTS. Phagocytosis of PMNs and monocytes was not significantly reduced in refractory anemia (RA), while in refractory anemia with excess of blasts (RAEB) and in chronic myelomonocytic leukemia (CMML) a clear decrease (p < 0.05) of this function was found in both PMNs and monocytes. The production of oxygen intermediates by PMNs and monocytes was significantly (p < 0.01) reduced in RA as well as in RAEB and in CMML. CONCLUSIONS. This study indicates the presence in myelodysplastic syndromes of a severe reduction in phagocytosis and oxygen intermediates production (two crucial functions to protect the host against pyogenic agents) in both PMNs and monocytes. This observation could explain the severe morbidity and mortality from infections in patients affected by these hematological malignancies.