Iron transport in the plasma is carried out by transferrin, which donates iron to cells through its interaction with a specific membrane receptor, the transferrin receptor (TfR). A soluble form of the TfR (sTfR) has been identified in animal and human serum. Soluble TfR is a truncated monomer of tissue receptor, lacking its first 100 amino acids, which circulates in the form of a complex of transferrin and its receptor. The erythroblasts rather than reticulocytes are the main source of serum sTfR. Serum sTfR levels average 5.0 F 1.0 mg/l in normal subjects but the various commercial assays give disparate values because of the lack of an international standard. The most important determinant of sTfR levels appears to be marrow erythropoietic activity which can cause variations up to 8 times below and up to 20 times above average normal values. Soluble TfR levels are decreased in situations characterized by diminished erythropoietic activity, and are increased when erythropoiesis is stimulated by hemolysis or ineffective erythropoiesis. Measurements of sTfR are very helpful to investigate the pathophysiology of anemia, quantitatively evaluating the absolute rate of erythropoiesis and the adequacy of marrow proliferative capacity for any given degree of anemia, and to monitor the erythropoietic response to various forms of therapy, in particular allowing to predict response early when changes in hemoglobin are not yet apparent. Iron status also influences sTfR levels, which are considerably elevated in iron deficiency anemia but remain normal in the anemia of inflammation, and thus may be of considerable help in the differential diagnosis of microcytic anemia. This is particularly useful to identify concomitant iron deficiency in a patient with inflammation because ferritin values are then generally normal. Elevated sTfR levels are also the characteristic feature of functional iron deficiency, a situation defined by tissue iron deficiency despite adequate iron stores. The sTfR/ferritin ratio can thus describe iron availability over a wide range of iron stores. With the exception of chronic lymphocytic leukemia (CLL) and high-grade non-Hodgkin's lymphoma and possibly hepatocellular carcinoma, sTfR levels are not increased in patients with malignancies. We conclude that soluble TfR represents a valuable quantitative assay of marrow erythropoietic activity as well as a marker of tissue iron deficiency. D

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Summary:Fifty patients affected by sickle cell anaemia underwent transplantation of HLA-identical haematopoietic stem cells (bone marrow, 48; cord blood, 2). Two groups of patients were considered for transplantation. Group 1 included 36 permanent residents of a European country who, retrospectively, met the inclusion criteria accepted at a consensus conference held in Seattle in 1990, wherein children were selected because they already had evidence of a morbid course. Group 2 included 14 patients who were transplanted earlier, had not received more than three blood transfusions and were transplanted because they had decided to return to their country of origin. Kaplan-Meier estimates of overall survival, event-free survival and disease-free survival at 11 years of the whole grafted population are 93, 82 and 85%, respectively. In group 1, overall survival, EFS and DFS were 88, 76 and 80% and in group 2, 100, 93 and 93%, respectively. Clinical manifestations of the disease, as well as disease associated haemolytic anaemia, disappeared in all successfully treated patients. Recovery of spleen function was present in seven out of 10 evaluated patients. Adverse events (death, absence of engraftment, mixed chimerism and relapse) occurred more frequently in group 1 than in group 2 (25% vs 7%, P Ͻ 0.001). Acute graft-versus-host disease (GVHD) was present in 20 patients (grade I or II, 19; grade III, 1), chronic GVHD in 10 (limited, 7; extensive, 3). One patient developed an acute myeloid leukaemia. Gonadal dysfunction was present in all patients (six boys and eight girls) transplanted close to or after puberty, although transient in one adolescent girl.

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