International forum. Use of umbilical cord blood progenitor cells as an alternative for bone marrow transplantation.
; ; et al
in Vox Sanguinis (2002), 83(2), 172-87Detailed reference viewed: 36 (0 ULg)
Stunting may determine the severity of malaria-associated anemia in African children.
; ; et al
in Pediatrics (2002), 110(4), 48
OBJECTIVE: Evidence from previous studies that malnourished children are protected against malaria is controversial. In individuals repeatedly exposed to malaria, immunity may develop first against severe ... [more ▼]
OBJECTIVE: Evidence from previous studies that malnourished children are protected against malaria is controversial. In individuals repeatedly exposed to malaria, immunity may develop first against severe disease, then against pyrogens, and last, against parasites. If this is true, this would suggest that reduced immune function that may exist in stunted children exacerbates the severity of malarial signs and symptoms, rather than the occurrence of parasitemia. On the other hand, several studies have suggested that malnourished children are protected to some degree against malaria. Our aim was to evaluate whether observational data support the hypothesis that nutritional inadequacies that cause stunting modify the associations between malaria and hematologic indicators such as hemoglobin concentration and serum concentrations of C-reactive protein and soluble transferrin receptor (sTfR). We showed earlier that increased serum concentrations of these receptors in asymptomatic malaria may be explained, at least in part, by increased erythropoiesis to compensate for malaria-induced hemolysis. METHODOLOGY: Community-based cluster survey among Kenyan children aged 2 to 36 months asymptomatic for malaria or anemia (n = 318). RESULTS: When adjusted for age and wasting, the malaria-associated decrease in mean hemoglobin concentration was 8.5 g/L and 15.8 g/L in nonstunted and stunted children, respectively. The malaria-associated increase in geometric mean serum concentrations of sTfR was 1.1-fold and 1.8-fold in nonstunted and stunted children, respectively. The malaria-associated increase in geometric mean serum concentrations of C-reactive protein was 1.4-fold and 2.3-fold in nonstunted and stunted children, respectively. Thus, children with malaria and those who were stunted suffered from more severe anemia and had higher serum concentrations of C-reactive protein and sTfR than would be expected from the combined effect of the 2 working independently. CONCLUSIONS: Our results are consistent with the notion that the nutritional inadequacies causing stunting also impair host immunity, thus increasing the degree to which malaria is associated with decreased concentrations of hemoglobin, with increased inflammation, and with increased iron demand in developing erythroblasts. Increased intake of micronutrients may not only reduce stunting and nutritional anemia, but also reduce malaria-associated anemia. [less ▲]Detailed reference viewed: 28 (2 ULg)
Prediction of response and other improvements on the limitations of recombinant human erythropoietin therapy in anemic cancer patients.
in Haematologica (2002), 87(11), 1209-21
BACKGROUND AND OBJECTIVES: The majority of cancer patients suffer from chronic anemia. While recombinant human erythropoietin (rHuEPO) offers many of the advantages of blood transfusions, response rates ... [more ▼]
BACKGROUND AND OBJECTIVES: The majority of cancer patients suffer from chronic anemia. While recombinant human erythropoietin (rHuEPO) offers many of the advantages of blood transfusions, response rates to this treatment are variable and in some trials a large proportion of patients (30 50%) did not respond. This failure may be due to factors related to the underlying disease, the chemotherapy given or functional iron deficiency. An accurate means of predicting response to rHuEPO would be beneficial to both healthcare providers and patients. EVIDENCE AND INFORMATION SOURCES: Data were identified by searches of the published literature, including PubMed, references from relevant reviews, and abstracts presented at recent international oncology and hematology meetings. Only papers in English published between 1990 and 2002 were included. References were selected according to direct relevance to the topic discussed and availability. STATE OF THE ART: The best algorithms for predicting response appear to be those combining an assessment of the adequacy of endogenous erythropoietin production together with some early indicators of erythropoietic marrow response. Further characterization of the dose-response relationship of erythropoietic agents may allow better understanding of ways in which response may be enhanced. Adequate iron availability could also contribute to better response rates. PERSPECTIVES: Further characterization of the predictors of response for current and upcoming erythropoietic agents may enhance the management of anemia associated with cancer, and provide more convenient, effective, and flexible therapy. [less ▲]Detailed reference viewed: 8 (0 ULg)
Comment etablir le bilan de fin de traitement des patients atteints de lymphomes non-hodgkiniens (LNH) de malignite intermediaire ou elevee?
; Jerusalem, Guy ; Hustinx, Roland et al
in Revue Médicale de Liège (2002), 57(12), 779-84
Incomplete regression of a lymphomatous mass after chemotherapy and/or radiotherapy constitutes a major problem in the treatment of lymphoma. In patients with persisting tumor, it could be reasonable to ... [more ▼]
Incomplete regression of a lymphomatous mass after chemotherapy and/or radiotherapy constitutes a major problem in the treatment of lymphoma. In patients with persisting tumor, it could be reasonable to use salvage therapy and possibly hematopoietic stem cell transplantation at the time of minimal disease rather than at the time of clinically overt relapse. The authors reviewed the most appropriate imaging techniques for the assessment of response to treatment. The limitations of CT and MRI for predicting the nature of residual masses are well known. 67Ga scintigraphy has become a standard procedure for the posttreatment evaluation of patients with lymphoma, but it appears that 18F-FDG PET may be a more effective method. Personal experience in the field of PET scan is reported. Although PET should be considered the noninvasive imaging modality of choice, a histological confirmation of residual disease is always necessary before starting salvage therapy. 18F-fluorodeoxyglucose is not a tumor specific radiotracer. [less ▲]Detailed reference viewed: 69 (2 ULg)
Outpatient and home parenteral antibiotic therapy (OHPAT) in low-risk febrile neutropenia: consensus statement of a Belgian panel.
Beguin, Yves ; ; et al
in Acta Clinica Belgica (2002), 57(6), 309-16
Febrile neutropenia requires adequate antibiotic treatment. A subgroup of patients are only at low risk for complications and could be treated at home/as outpatients (OHPAT) after a short initial ... [more ▼]
Febrile neutropenia requires adequate antibiotic treatment. A subgroup of patients are only at low risk for complications and could be treated at home/as outpatients (OHPAT) after a short initial admission for work up. This position paper by a Belgian panel of experts presents criteria defining low-risk in febrile neutropenia, gives an overview of the existing experience and examines the present obstacles to a more widespread use of OHPAT in this country. [less ▲]Detailed reference viewed: 46 (2 ULg)
Predictive factors for response of anemia to recombinant human erythropoietin
in Nowrousian, M. R. (Ed.) Recombinant human erythropoietin (rhEPO) in clinical oncology (2002)Detailed reference viewed: 6 (0 ULg)
Despite inhibition of hematopoietic progenitor cell growth in vitro, the tyrosine kinase inhibior STI571 does not impair engraftment of human CD34+ cells into NOD/SCIDB2mNull mice
Pirson, Laurence ; Baron, Frédéric ; Giet, Olivier et al
Poster (2002)Detailed reference viewed: 17 (11 ULg)
Increased binding and defective migration across fibronectin of cycling hematopoietic progenitor cells.
Giet, Olivier ; ; et al
in Blood (2002), 99(6), 2023-31
Engraftment of hematopoietic progenitor cells has been shown to decrease during cell cycle transit. We studied cell cycle-associated changes in adhesion and migration of mitotically activated cord blood ... [more ▼]
Engraftment of hematopoietic progenitor cells has been shown to decrease during cell cycle transit. We studied cell cycle-associated changes in adhesion and migration of mitotically activated cord blood CD34+ cells. Migration toward medium conditioned by the stromal-derived factor-1-producing cell line MS-5 was studied in bovine serum albumin- and fibronectin (Fn)-coated transwells. Migration was reduced in cycling CD34+ cells and long-term culture-initiating cells (LTC-ICs) compared with their noncycling counterparts across Fn but not across bovine serum albumin. Conversely, Fn binding was higher in cycling CD34+ cells and LTC-ICs compared with noncycling progenitor cells, while adhesion of both subsets to bovine serum albumin was undetectable. The contribution of alpha4 and alpha5 integrins in mediating adhesion and migration of activated CD34+ cells onto Fn was analyzed by neutralization experiments. While alpha4-mediated Fn binding decreased during G(2)/M, alpha5 integrin-mediated adhesion increased during transit from G(0)/G(1) to S and G(2)/M phases. As for migration, the contribution of alpha4 integrin was similar in all phases, whereas alpha5-directed migration was lower in G(2)/M compared with G(0)/G(1) and S phases. Defective migration of cycling CD34+ cells was not due to differences in alpha5 integrin expression. In conclusion, chemotaxis across Fn is less efficient in cycling progenitor cells in correlation with an increased Fn binding capacity. In addition, alpha4 and alpha5 integrin functions are independently modulated during cell cycle transit. [less ▲]Detailed reference viewed: 110 (3 ULg)
Adhesion of synchronized human hematopoietic progenitor cells to fibronectin and vascular cell adhesion molecule-1 fluctuates reversibly during cell cycle transit in ex vivo culture.
; Giet, Olivier ; et al
in Blood (2002), 100(8), 2744-52
Ex vivo expansion of hematopoietic stem/progenitor cells may result in defective engraftment. Human cord blood CD34(+) progenitor cells were synchronized and assayed for adhesion and migration onto ... [more ▼]
Ex vivo expansion of hematopoietic stem/progenitor cells may result in defective engraftment. Human cord blood CD34(+) progenitor cells were synchronized and assayed for adhesion and migration onto fibronectin (Fn) and vascular cell adhesion molecule-1 (VCAM-1) at different stages of a first cell cycle executed ex vivo. During S phase transit, adhesion to Fn was transiently increased while binding to VCAM-1 was reversibly decreased, after which adhesion to both ligands returned to baseline levels with cell cycle completion. Transmigration across Fn and VCAM-1 decreased irreversibly during S phase progression. The function of alpha4 and alpha5 integrins was assessed with specific neutralizing antibodies. In uncultured CD34(+) cells and long-term culture-initiating cells (LTC-ICs), both adhesion and migration on Fn were inhibited by anti-alpha4 but not by anti-alpha5 antibodies. In mitotically activated CD34(+) cells and LTC-ICs, adhesion and migration on Fn were mainly dependent on alpha5 integrin and to a lesser extent on alpha4 integrin. Changes in integrin function were not dependent on parallel modulation of integrin expression. In conclusion, Fn and VCAM-1 binding of progenitor cells fluctuates reversibly during cell cycle transit ex vivo. In addition, our data show that mitogenic activation induces a shift from a dominant alpha4 to a preferential alpha5 integrin-dependent interaction with Fn. [less ▲]Detailed reference viewed: 83 (3 ULg)
Monitoring of erythropoiesis by the serum transferrin receptor and erythropoietin.
Fillet, Georges ; Beguin, Yves
in Acta Clinica Belgica (2001), 56(3), 146-54
Virtually all cells have transferrin receptors (a transmembrane glycoprotein) on their surface but in a normal adult, 80% of them are in the erythroid marrow. Some of them are lost into the circulation ... [more ▼]
Virtually all cells have transferrin receptors (a transmembrane glycoprotein) on their surface but in a normal adult, 80% of them are in the erythroid marrow. Some of them are lost into the circulation where they can be measured by immuno-assays. A direct and highly significant correlation exists between serum transferrin receptor level and erythron transferrin uptake in humans. The measurement of serum transferrin receptor has wide clinical applications for the quantitation of erythropoiesis. It can be used to study erythropoiesis in situations in which ferrokinetics is not acceptable such as pregnancy. It is particularly useful for serial studies, e.i., for monitoring the recovery of erythropoiesis after stem cell transplantation or after treatment with erythropoietin. Combined with the determination of serum erythropoietin, both evaluated in relation to the degree of anemia, they provide a physiological approach to the diagnosis of anemia. Thus, the simultaneous determination of hematocrit, reticulocytes, serum transferrin receptor and serum erythropoietin has high discriminatory value in distinguishing between a defect in erythroid proliferation, maturation or red cell survival. It is also particularly useful for detecting the presence of multiple mechanisms of anemia in the same patient. [less ▲]Detailed reference viewed: 21 (1 ULg)
Intérêt du dosage du récepteur soluble de la transferrine (sTfR) pour l'évaluation de l'érythropoïèse et de l'état du fer
in Hématologie (2001), 7Detailed reference viewed: 28 (4 ULg)
Whole-body positron emission tomography using 18F-fluorodeoxyglucose compared to standard procedures for staging patients with Hodgkin's disease.
Jerusalem, Guy ; Beguin, Yves ; Fassotte, Marie-France et al
in Haematologica (2001), 86(3), 266-73
BACKGROUND AND OBJECTIVES: Accurate staging is essential in order to determine appropriate treatment in Hodgkin's disease (HD). (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) offers ... [more ▼]
BACKGROUND AND OBJECTIVES: Accurate staging is essential in order to determine appropriate treatment in Hodgkin's disease (HD). (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) offers the advantage of metabolic imaging that is largely independent of morphologic criteria. In the present study we evaluated the role of (18)F-FDG PET compared to routine procedures for the staging of patients with HD. DESIGN AND METHODS: Thirty-three patients with HD underwent standard staging procedures (clinical examination, laboratory screening, chest X-ray, computed tomography (CT) of the chest and abdomen and bilateral bone marrow biopsies) and a whole-body (18)F-FDG PET study. In clinical examination, an isolated lymph node > 1 cm or multiple lymph nodes > or = 1 cm in size were considered abnormal. Positive findings at both clinical examination or CT and (18)F-FDG PET were regarded as actual locations of disease. Negative findings with both methods were regarded as true negative (no involvement by HD). In cases of discrepancy, response to treatment and follow-up data were used to assess the overall accuracy of the patient's original evaluation. RESULTS: Completely concordant results in lymph node staging were observed in 20 patients. The two staging procedures indicated complementary information in 1 patient. Conventional staging indicated more pathologic lymph node areas in 6 patients (at least 1 false positive). (18)F-FDG PET showed more sites in 6 patients. The sensitivity of (18)F-FDG PET in detecting all known pathologic lymph nodes was 83% for peripheral lymph nodes, 91% for thoracic lymph nodes and 75% for abdominal and pelvic lymph nodes. Conventional staging procedures and (18)F-FDG PET indicated the same tumor stage in 26 patients. Based on (18)F-FDG PET, downstaging was suggested in 4 patients, including a biopsy-proven case. However in 1 of these cases this was incorrect. (18)F-FDG PET suggested upstaging in 3 patients. Based on conventional staging or (18)F-FDG PET the same treatment strategy was defined in 32 patients. In one patient (18)F-FDG PET downstaged disease extension (stage IIIA-->IIA) that would have suggested radiotherapy as a possible treatment option. INTERPRETATION AND CONCLUSIONS: (18)F-FDG PET provides an easy and efficient whole-body method for the evaluation of patients with HD. (18)F-FDG PET never missed tumor masses >1 cm. (18)F-FDG PET detected additional sites of disease not seen by conventional procedures and identified absence of disease in some sites suspected to be involved. However, in our patients this did not translate into changes in treatment strategy. [less ▲]Detailed reference viewed: 39 (1 ULg)
Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) for the staging of low-grade non-Hodgkin's lymphoma (NHL).
Jerusalem, Guy ; Beguin, Yves ; et al
in Annals of Oncology (2001), 12(6), 825-30
BACKGROUND: Although PET has been shown to be highly sensitive in the primary staging of lymphoma, previous studies with small numbers of patients indicated that low-grade NHL may not always be adequately ... [more ▼]
BACKGROUND: Although PET has been shown to be highly sensitive in the primary staging of lymphoma, previous studies with small numbers of patients indicated that low-grade NHL may not always be adequately detected by PET. We undertook this study to determine factors influencing the detection of lesions by PET in low-grade NHL and to evaluate the utility of PET in this indication. PATIENTS AND METHODS: Forty-two patients underwent conventional staging procedures (clinical examination, oto-rhino-laryngologic examination, computed tomography of the chest, abdomen and pelvis, gastroscopy and bone marrow biopsy as well as whole-body non-attenuation corrected 18F-FDG-PET RESULTS: PET detected 40% more abnormal lymph node areas than conventional staging in follicular lymphoma but was inappropriate for the staging of small lymphocytic lymphoma where it detected less than 58% of abnormal lymph node areas. PET showed more lesions than conventional staging for peripheral (34% more lymph node areas detected) and thoracic lymph node (39% more) areas but not for abdominal or pelvic lymph nodes (26% fewer areas detected). The sensitivity to detect bone marrow infiltration was unacceptably low for PET. In contrast, PET was as effective as standard procedures for the detection of other extranodal localizations, although a few localizations were detected only by PET and a few others only by conventional procedures. CONCLUSIONS: PET may contribute to the management of patients with low-grade follicular NHL. For the other low-grade lymphoma subtypes, the role of PET is less evident. Further studies using PET to evaluate the results of treatment or to diagnose disease recurrence are warranted in low-grade follicular NHL. [less ▲]Detailed reference viewed: 65 (19 ULg)
Treatment of leukemia relapse after allogeneic hematopoietic stem cell transplantation by donor lymphocyte infusion and STI-571.
Baron, Frédéric ; Frere, Pascale ; Fillet, Georges et al
in Haematologica (2001), 86(9), 993-4Detailed reference viewed: 18 (0 ULg)
Administration of erythopoietin and granulocyte colony-stimulating factor in donor/recipient pairs to collect peripheral blood progenitor cells (PBPC) and red blood cell units for use in the recipient after allogeneic PBPC transplantation.
Sautois, Brieuc ; Baudoux, Etienne ; Salmon, Jean et al
in Haematologica (2001), 86(11), 1209-18
BACKGROUND AND OBJECTIVES: It may be useful to reduce the exposure of transplant recipients to homologous blood. This may be achieved by procuring donor-derived red blood cell (RBC) units, collecting more ... [more ▼]
BACKGROUND AND OBJECTIVES: It may be useful to reduce the exposure of transplant recipients to homologous blood. This may be achieved by procuring donor-derived red blood cell (RBC) units, collecting more peripheral blood progenitor cells (PBPC) with a combination of granulocyte colony-stimulating factor (G-CSF) + recombinant human erythropoietin (rHuEpo) and by administering rHuEpo post-transplantation. DESIGN AND METHODS: Eight ABO-compatible donors were treated with rHuEpo and intravenous iron to collect 12 RBC units for use in their recipients. PBPC were collected after mobilization with rHuEpo and G-CSF in the same donors. The recipients received G-CSF and rHuEpo post-transplantation. A control group of 10 donor/recipient pairs received G-CSF alone for PBPC mobilization and after the transplantation. RESULTS: Eighty-six out of 91 planned RBC units were collected in the donors without significant decrease in hematocrit because of a 4-fold increase in RBC production despite functional iron deficiency. After 2 leukaphereses, the cumulative yields of NC and CFU-GM were lower in the study group while those of BFU-E, CFU-Mix and CD34+ cells were similar. However, erythroid recovery was significantly accelerated in the study group. INTERPRETATION AND CONCLUSIONS: Collection of 12 RBC units within 6 weeks is feasible with rHuEpo and intravenous iron; this strategy allows a dramatic reduction in recipient exposure to homologous blood; rHuEpo has no synergistic effect with G-CSF for mobilization of PBPC in normal donors and may even be deleterious; and rHuEpo in the recipient may enhance erythroid engraftment. [less ▲]Detailed reference viewed: 60 (4 ULg)
Nouvelles approches thérapeutiques puor l'hypernéphrome métastasique
; Jerusalem, Guy ; Sautois, Brieuc et al
in Médecine et Hygiène (2001), 59Detailed reference viewed: 407 (25 ULg)
Place de la tomographie d'émission de positons dans le suivi thérapeutique du cancer du sein
Jerusalem, Guy ; ; et al
in Médecine Nucléaire : Imagerie Fonctionnelle et Métabolique (2001), 25(6), 341-346
La tomographie à émission de positons (TEP) au 18F-fluorodeoxyglucose (FDG) fait l'objet d'un nombre croissant d'applications cliniques en oncologie surtout dans le bilan d'extension et le bilan de fin de ... [more ▼]
La tomographie à émission de positons (TEP) au 18F-fluorodeoxyglucose (FDG) fait l'objet d'un nombre croissant d'applications cliniques en oncologie surtout dans le bilan d'extension et le bilan de fin de traitement. Un domaine très prometteur mais peu étudié est l'utilisation de la TEP dans l'évaluation thérapeutique précoce. Nous passons en revue les données de la littérature concernant la place de la TEP dans l'évaluation précoce de la réponse thérapeutique chez des patientes atteintes de cancer du sein. La TEP permet d'identifier précocement les patientes qui ont une grande probabilité de présenter une réponse tumorale facorable à une chimiothérapie néoadjuvante (chimiothérapie première). Cependant, non propres travaux chez des patientes atteintes de cancer du sein métastatique sont moins prometteurs. La poursuite des travaux de recherche est indispensable pour mieux connaître le bénéfice réel et les limites d'une évaluation thérapeutique précoce. [less ▲]Detailed reference viewed: 43 (3 ULg)
Reticulocyte transferrin receptor (TfR) expression and contribution to soluble TfR levels.
R'Zik, Samir ; ; Beguin, Yves
in Haematologica (2001), 86(3), 244-51
BACKGROUND AND OBJECTIVES: Transferrin receptor (TfR) expression in erythroid cells is regulated by a number of factors, including iron status and erythropoietin (Epo) stimulation. However, the impact of ... [more ▼]
BACKGROUND AND OBJECTIVES: Transferrin receptor (TfR) expression in erythroid cells is regulated by a number of factors, including iron status and erythropoietin (Epo) stimulation. However, the impact of these factors on reticulocyte TfR expression in vivo has never been studied. A soluble form of TfR (sTfR) is present in serum in proportion to the mass of cellular TfR. Although sTfR shedding by reticulocytes and erythroblasts has been demonstrated in vitro, the contribution of reticulocyte TfR to serum sTfR has never been evaluated in vivo. DESIGN AND METHODS: We measured directly the total number of reticulocyte TfR in normal rats of different age and iron status, as well as in animals experiencing various conditions and treatments aimed at altering erythropoietic activity and iron status, including rHuEpo therapy, hemolytic anemia, phlebotomies, hypertransfusions, thiamphenicol-induced red cell aplasia or inflammation. In addition, we examined the impact of repeated hypertransfusions with normal, reticulocyte-poor and reticulocyte-rich blood on serum sTfR levels. RESULTS: The number of TfR molecules per reticulocyte was around 50,000 in young rats but was around 100,000 in older animals. These values remained constant in most conditions and in particular were not influenced by iron supplementation or iron overload. However, functional iron deficiency as well as rHuEpo therapy resulted in increased reticulocyte TfR expression. In addition, TfR numbers in reticulocytes were elevated in the early phase of recovery after acute hemolysis or red cell aplasia but normalized soon after. Hypertransfusion experiments clearly demonstrated that reticulocytes can contribute substantially to sTfR levels in vivo. INTERPRETATION AND CONCLUSIONS: TfR numbers are regulated in vivo by the same factors as in vitro, in particular iron deficiency and erythropoietin stimulation. Circulating reticulocytes contribute significantly to serum sTfR levels. [less ▲]Detailed reference viewed: 85 (1 ULg)
Serum soluble transferrin receptor concentration is an accurate estimate of the mass of tissue receptors.
R'Zik, Samir ; Beguin, Yves
in Experimental hematology (2001), 29(6), 677-85
OBJECTIVE: Serum levels of the soluble transferrin receptor (sTfR) vary depending on the erythropoietic activity and iron status. In vitro, sTfR shed in the incubation medium correlates well with cellular ... [more ▼]
OBJECTIVE: Serum levels of the soluble transferrin receptor (sTfR) vary depending on the erythropoietic activity and iron status. In vitro, sTfR shed in the incubation medium correlates well with cellular TfR, but this relationship has never been established in vivo. To determine the value of serum sTfR as a quantitative marker of the body mass of tissue TfR, we designed experiments to examine the correlation between serum sTfR and tissue TfR in rats with various degrees of erythropoietic activity or iron status. MATERIALS AND METHODS: We studied changes in erythropoietic activity in normal rats as well as in animals experiencing hemolysis, phlebotomy-induced iron deficiency, transfusion- or thiamphenicol-induced erythroid aplasia, or inflammation. At the end of follow-up, ferrokinetic studies were performed and animals were sacrificed. Organs were isolated and homogenized to determine the total mass of tissue TfR from the sum of tissue solubilized TfR in the bone marrow, spleen, liver, and blood cells (direct method). An indirect method was developed to derive the corporeal mass of tissue TfR from a representative marrow sample. RESULTS: As expected, serum sTfR and total mass of tissue TfR varied as a function of iron status and erythropoiesis. Relative erythroid expansion in the spleen was greater than in the bone marrow. With the exception of phlebotomized animals, the indirect method correlated very well with direct measurements of the total mass of tissue TfR (r = 0.97, p < 0.0001). There was a close relationship between the total mass of tissue TfR and the total mass of serum sTfR (r = 0.79, p < 0.0001). Serum sTfR represented approximately 5-6% of the total mass of tissue TfR in most experimental situations, but this ratio was twice as high during iron-restricted erythropoiesis. In addition, the ratio could be higher or lower in nonsteady-state situations, because changes in tissue TfR occurred faster than those of serum sTfR. CONCLUSIONS: Serum sTfR represents a constant proportion of the total mass of tissue TfR over a wide range of erythropoietic activity. However, iron deficiency results in a higher proportion of serum sTfR, and the pace of change in serum sTfR levels is slower than that of tissue TfR mass. [less ▲]Detailed reference viewed: 148 (7 ULg)