Altered surface expression of effector cell molecules on neutrophils in myelodysplastic syndromes.

The surface expression of effector cell molecules on neutrophils was examined in 18 patients with myelodysplastic syndromes (MDS) and 20 healthy control subjects. The MDS patients were further classified as low clinical risk (L-MDS, n=7) and high clinical risk (H-MDS, n=11). The expression of Fc receptors for IgG (FcR), complement receptors (CR) and cellular adhesion molecules on neutrophils was determined by flow cytometry and monoclonal antibodies. The effect of granulocyte colony-stimulating factor (G-CSF) and tumour necrosis factor-alpha (TNF) on L-selectin shedding and CR up-regulation on neutrophils was also examined. The percentage of FcRI-positive neutrophils and CD11b/CR3 expression on neutrophils were significantly increased in the H-MDS patients when compared to the controls. In contrast, the expression of FcRII, FcRIII, L-selectin, LFA-1 and CD18 on neutrophils was significantly reduced in the H-MDS patients compared with the controls. The L-MDS neutrophils exhibited lower expressions of CR1, L-selectin, LFA-1 and CD18 than those of the controls. Neutrophils from some H-MDS patients showed impaired L-selectin shedding and CR up-regulation after stimulation with G-CSF or TNF, although these were not significantly different when assessed in the whole H-MDS group. These findings suggest that an altered surface expression of effector cell molecules and an impaired modulation of cellular adhesion molecules on neutrophils may contribute to the increased susceptibility to bacterial infections in MDS patients.