Aberrant expression of the major sialoglycoprotein (CD43) on the monocytesof patients with myelodysplastic syndromes

CD43, a sialylated glycoprotein expressed on the surface of most hematopoie tic cells, has been implicated in cell adhesion and signaling. The reduced expression of this antigen in patients with Wiscott-Aldrich syndrome, in wh ich progressive immunodeficiency is a major problem, raised the question wh ether abnormal expression of this molecule could affect the susceptibility to infections in patients with myelodysplastic syndromes (MDS). We studied the expression of this antigen on the monocytes of ten patients with chroni c myelomonocytic leukemia (CMML) and compared the results with 67 patients suffering from other MDS syndromes and with 18 healthy individuals. We chos e this series as it plays an important role in MDS patients where in most c ases the neutrophils are defective. We also examined the following antigens as indicative of activation and adhesion of the monocytes in these patient s: CD11b, CD18, CD35, CD38, CD44, CD69. We found decreased expression of CD 43 on the monocytes of the RA, RAS, RAEB, and RAEB-t patients compared with the CMML and controls. The other activation molecules studied were found t o be upregulated, suggesting the existence of activated monocytes in these patients. The increased levels of soluble vascular cell adhesion molecule i n these patients suggest vascular endothelial activation in the absence of infection. Further experiments are needed to investigate the significance o f CD43 downregulation in these patients, its role in cell adherence and tis sue migration, and the correlation of the phenomenon to the increased susce ptibility to infections observed in these patients.