Activation of monocyte-derived cells in the bone marrow of myelodysplastic syndrome.

To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS).,Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells - morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA).,About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years.,The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS.