Immunohistochemical assessment of human bone marrow macrophages in hematologic disorders

Changes in bone marrow macrophages may be associated with abnormal hematopo iesis in various hematologic disorders. We immunohistochemically evaluated the density of macrophages in bone marrow trephine biopsies, in reactive er ythroid hyperplasia (hemolytic anemia and megaloblastic anemia), the macrop hages slightly increased in density, extending their cytoplasmic processes between hematopoietic cells. In erythroid hypoplasia (pure red cell aplasia ), they became rounded and frequently had hemosiderin granules. There was n o significant difference in the macrophage density in the hematopoietic are a between erythroid hyperplasia and hypoplasia. The macrophages increased i n density in myeloproliferative disorders (polycythemia vera, chronic myelo genous leukemia and primary thrombocythemia). In myelofibrosis, some macrop hages became extremely elongated along the line of the fibroblastic cells. In contrast, in conditions in which myelopoietic activity is considerably i mpaired (aplastic anemia, acute leukemia and multiple myeloma), they signif icantly decreased in density. These results suggest that the morphologic ch ange In bone marrow macrophages is associated with erythropoietic activity and that there is a correlation between macrophage density and myelopoietic activity.