Immunophenotypic characterization of myelomonocytic cells in patients with myelodysplastic syndrome.

Infections, an important determining factor in the clinical course of myelodysplastic syndromes (MDS), result in activation of myelomonocytic cells. In this study we demonstrate activation-associated immunophenotypic changes of cell surface antigens on monocytes and granulocytes observed in two groups of MDS patients, one with low and another one with high clinical risk, and compared them to healthy individuals. Significantly changed expression of the complement receptors 1 (CD35) and 3 (CD11b), the Fc gamma receptor I (CD64), the leucocyte-homing receptor (CD44) and the activation associated membrane proteins CD67 and M5 were found on monocytes and/or granulocytes of MDS patients. In low-risk MDS patients we observed activation-associated phenotypic changes only in monocytes, whereas in high-risk MDS patients, both monocytes and granulocytes showed such changes. Additionally, we performed respiratory burst experiments and observed an impaired response of monocytes and granulocytes derived from MDS patients. Despite the fact that all patients were free of infection by clinical criteria, cell surface phenotyping as well as the reduced respiratory burst capacity of myelomonocytic cells suggests in vivo preactivation of these cells.