Tissue uptake of circulating thrombopoietin is increased in immune-mediated compared with irradiated thrombocytopenic mice. (9/2217)

We have previously demonstrated a significant inverse correlation between circulating thrombopoietin (TPO) levels and peripheral platelet (PLT) counts in patients with thrombocytopenia secondary to megakaryocytic hypoplasia but not in patients with immune thrombocytopenic purpura (ITP; Chang et al, Blood 88:3354, 1996). To test the hypothesis that the differences in the circulating TPO levels in these two types of thrombocytopenia are caused by differences in the total capacity of Mpl receptor-mediated TPO clearance, thrombocytopenia was induced in female CD-1 mice either by sublethal irradiation (irradiated) or rabbit antimouse PLT serum (RAMPS) for 1 day (1 d RAMPS) and 5 days (5 d RAMPS). A well-characterized murine model of autoimmune thrombocytopenic purpura, male (NZW x BXSB) F1 mice (W/B F1), was also included in this study. All thrombocytopenic mice and their controls received trace amounts of 125I-recombinant murine TPO (125I-rmTPO) intravenously and were killed 3 hours postinjection. Blood cell-associated radioactivity was significantly decreased in all 4 groups of thrombocytopenic mice. Significantly increased plasma and decreased whole spleen-associated radioactivity was observed in the irradiated group compared with controls (P <.05). While a lesser but still significant increase in plasma and decrease in whole spleen-associated radioactivity was observed in the 1 d RAMPS mice (P <.05), there were no significant differences between the 5 d RAMPS nor the W/B F1 male mice compared with controls, although whole spleen-associated radioactivity was higher in the W/B F1 male. A significant inverse correlation of plasma and whole spleen-associated radioactivity was demonstrated in W/B F1 male mice (r = -.91, n = 6, P <.05). There was also a decrease in bone (femur)/blood-associated radioactivity in the irradiated group compared with controls (P <.05), but a significant increase in 1 d and 5 d RAMPS mice (P <.01). Furthermore, the 125I-rmTPO uptake capacity within the spleen and marrow of immune thrombocytopenic mice appeared to be associated with a higher megakaryocytic mass when tissue samples were examined by light microscopy. Internalization of 125I-rmTPO by megakaryocytes and PLTs in the spleens and marrows of ITP mice was also demonstrated directly using electron microscopic autoradiography. Labeled PLTs were also found within splenic macrophages. Additionally, the mean PLT volumes of RAMPS mice were significantly higher than those of the control and irradiated mice (P <.05), as was the bound 125I-rmTPO (cpm) per million PLT (P <.05). Finally, significantly decreased 125I-rmTPO degradation products were only found in the plasma of the irradiated mice compared with control animals (P <.05). These data suggest that the lack of Mpl+ cells in the mice with thrombocytopenia secondary to megakaryocytic hypoplasia (irradiated) results in decreased uptake and degradation of TPO and higher circulating TPO levels. Furthermore, these data also suggest that, after a brief TPO surge in response to immune thrombocytopenia (1 d RAMPS), the lack of an inverse correlation of circulating TPO with PLT counts during steady-state immune thrombocytopenic mice (5 d RAMPS + W/B F1 male) is due, at least in part, to its uptake and degradation by the high PLT turnover and increased mass of megakaryocytes.  (+info)

Individual propensity for arterial thrombosis. (10/2217)

Arterial thrombophilia independent of vascular pathology has not been previously defined either experimentally or epidemiologically. To address the existence of an individual propensity to arterial thrombosis, we exploited a previously developed procedure entailing traumatic (crush) injury of paired porcine carotid arteries for generating platelet-rich thrombi. Porcine carotid arteries were injured bilaterally by serial hemostat crushes. Thrombus generation was monitored by local accumulation of autologous 111In-labeled platelets and Doppler blood flow. Within this cohort of animals of similar age and size, the lowest to the highest responders in thrombus mass spanned a 7-fold range, showing no correlation with shear, platelet or leukocyte count, or plasma concentrations of fibrinogen or von Willebrand factor. However, there was strong intra-individual correlation (r2=0.80; P<0.001) of thrombus deposition between carotid artery pairs. The wide variation in thrombotic response to a standardized stimulus, not accounted for by shear stress or typical hematological variables, appears to be an intrinsic propensity of the individual. The experimental system for thrombus generation is sufficiently quantitative for assessment of variables determining this propensity.  (+info)

Treatment with interleukin-2 (IL-2) and interferon (IFN(alpha 2b)) after autologous bone marrow or peripheral blood stem cell transplantation in onco-hematological malignancies with a high risk of relapse. (11/2217)

Nine patients with onco-hematological malignancies with a poor prognosis due to high risk of relapse received immunotherapy with interleukin-2 (IL-2) and interferon (IFN(alpha 2b)) s.c. as maintenance therapy after receiving autologous bone marrow or peripheral blood stem cell transplantation (ABMT/PBSCT). All the patients were considered at very high risk of relapse. We attempted to assess the efficiency, toxicity and clinical effects of these cytokines in these patients. Five patients were treated with high-dose of IL-2 and the other four patients with escalating doses every month. Side-effects in the first group of patients consisted of fever, chills, weakness, nausea, anorexia, loss of weight and local dermatitis in the injection site. Toxicity on the WHO scale was grade II in three patients and grade IV in the other two patients. In the second group of patients, the same clinical signs of toxicity appeared, but these were grade I on the WHO scale in all patients. None of the patients had infections or died in relation to administration of IL-2. Four patients died of relapse or progression of their hematological malignancies. The other five patients are alive, one in chronic phase of CML and the other four patients are in complete remission of their malignancies.  (+info)

The role of the human Fc receptor Fc gamma RIIA in the immune clearance of platelets: a transgenic mouse model. (12/2217)

In humans, the Fc receptor for IgG, FcgammaRIIA, is expressed on macrophages and platelets and may play an important role in the pathophysiology of immune-mediated thrombocytopenia. Mice lack the genetic equivalent of human FcgammaRIIA. To better understand the role of FcgammaRIIA in vivo, FcgammaRIIA transgenic mice were generated and characterized. One transgenic mouse line expressed FcgammaRIIA on platelets and macrophages at levels equivalent to human cells, and cross-linking FcgammaRIIA on these platelets induced platelet aggregation. Immune-mediated thrombocytopenia in this transgenic line was studied using i.v. and i.p. administration of anti-mouse platelet Ab. In comparison with matched wild-type littermates that are negative for the FcgammaRIIA transgene, Ab-mediated thrombocytopenia was significantly more severe in the FcgammaRIIA transgenic mice. In contrast, FcR gamma-chain knockout mice that lack functional expression of the Fc receptors FcgammaRI and FcgammaRIII on splenic macrophages did not demonstrate Ab-mediated thrombocytopenia. We generated FcgammaRIIA transgenic x FcR gamma-chain knockout mice to examine the role of FcgammaRIIA in immune clearance in the absence of functional FcgammaRI and FcgammaRIII. In FcgammaRIIA transgenic x FcR gamma-chain knockout mice, severe immune thrombocytopenia mediated by FcgammaRIIA was observed. These results demonstrate that FcgammaRIIA does not require the FcR gamma-chain for expression or function in vivo. Furthermore, taken together, the data suggest that the human Fc receptor FcgammaRIIA plays a significant role in the immune clearance of platelets in vivo.  (+info)

Intrauterine management of fetal parvovirus B19 infection. (13/2217)

OBJECTIVES: The aim of our study was to determine the outcome of pregnancies after intrauterine management of fetal parvovirus B19 infection. DESIGN: Retrospective study. SUBJECTS: A total of 37 cases of maternofetal parvovirus B19 infection, 35 of which were associated with hydrops fetalis, were referred to our tertiary level center between 1989 and 1996. With regard to fetal hydrops, no apparent cause other than parvovirus B19 infection was found in any patient. METHODS: In all patients, cordocentesis was performed to assess the degree of fetal anemia. When anemia was present, cordocentesis was followed by intrauterine transfusion with packed red cells into the umbilical vein. Further management depended on the degree of fetal anemia and gestational age and included follow-up fetal blood sampling/transfusion as well as ultrasound examinations as deemed appropriate. RESULTS: Packed red cell transfusion was performed in 30 patients with significant fetal anemia (Z-score 1.6-7.8 below the mean for gestational age). The fetal hemoglobin values ranged from 2.1 to 9.6 g/dl. Serum levels of platelets in the transfusion group were 9-228 x 10(9)/l with Z-scores in the range of < 1 to 3.8 below the mean. During treatment and follow-up, there were five intrauterine deaths (13.5%), one neonatal death (2.7%) and 31 live births (83.8%). CONCLUSIONS: Fetal parvovirus infection can lead to marked anemia and hydrops formation. Cordocentesis allows precise assessment of fetal anemia which can then be corrected by intravenous transfusion. Under this regimen, the outcome proved favorable in the majority of fetuses, even those that were severely anemic.  (+info)

Thrombopoietin concentrations are low in patients with cirrhosis and thrombocytopenia and are restored after orthotopic liver transplantation. (14/2217)

BACKGROUND: Thrombocytopenia in cirrhotic patients may be due to deficient production of thrombopoietin. AIMS: To determine the relation between thrombopoietin and thrombocytopenia in cirrhotic patients before and after orthotopic liver transplantation. METHODS: Thrombopoietin concentrations and platelet counts were measured in 43 cirrhotic patients and 21 normal controls and serially for 14 days after transplantation in 23/43 patients. RESULTS: 27 of the 43 patients had thrombocytopenia (platelet count less than 120 x 10(9)/l; group 1) whereas 16 patients had normal platelet count (group 2). Thrombopoietin concentrations were lower in group 1 than in group 2 (92.5 (20.3-286.3) v 226.6 (30.1-848.3) pg/ml, p=0.003) and normal controls (92.5 (20.3-286.3) v 158.3 (22.5-232.9) pg/ml, p=0.028). Post-transplantation thrombopoietin concentrations increased with a peak at day 5. The rise was significant in patients with low pretransplantation platelet count (89.1 (21.29-247.6) to 545.1 (66.2-2569) pg/ml; n=16, p=0.001) but not in those with normal platelet count (262.8 (30.1-848.3) to 315.1 (114-954.6) pg/ml; n=7, p=0.47). No correlation was found pretransplantation between spleen volume and platelet count (r=-0.11, p=0.6) or thrombopoietin concentrations (r=-0.04, p=0.8). However, pretransplantation thrombopoietin concentrations correlated with platelet count (r=0.47, p=0.0015), whereas an inverse correlation was found between peak thrombopoietin concentrations and nadir platelet count (r=-0.41 p=0. 049) post-transplantation. CONCLUSIONS: Inadequate thrombopoietin production may contribute to cirrhotic thrombocytopenia. Thrombopoietin production is restored after liver transplantation leading to the resolution of thrombocytopenia.  (+info)

Recombinant human thrombopoietin in combination with granulocyte colony-stimulating factor enhances mobilization of peripheral blood progenitor cells, increases peripheral blood platelet concentration, and accelerates hematopoietic recovery following high-dose chemotherapy. (15/2217)

Lineage-specific growth factors mobilize peripheral blood progenitor cells (PBPC) and accelerate hematopoietic recovery after high-dose chemotherapy. Recombinant human thrombopoietin (rhTPO) may further increase the progenitor-cell content and regenerating potential of PBPC products. We evaluated the safety and activity of rhTPO as a PBPC mobilizer in combination with granulocyte colony-stimulating factor (G-CSF) in 29 breast cancer patients treated with high-dose chemotherapy followed by PBPC reinfusion. Initially, patients received escalating single doses of rhTPO intravenously (IV) at 0.6, 1.2, or 2.4 micrograms/kg, on day 1. Subsequent patients received rhTPO 0.6 or 0.3 micrograms/kg on days -3, -1, and 1, or 0.6 micrograms/kg on days -1 and 1. G-CSF, 5 micrograms/kg IV or subcutaneously (SC) twice daily, was started on day 3 and continued through aphereses. Twenty comparable, concurrently and identically treated patients (who were eligible and would have been treated on protocol but for the lack of study opening) mobilized with G-CSF alone served as comparisons. CD34(+) cell yields were substantially higher with the first apheresis following rhTPO and G-CSF versus G-CSF alone: 4.1 x 10(6)/kg (range, 1.3 to 17.6) versus 0.8 x 10(6)/ kg (range, 0.3 to 4.2), P =.0003. The targeted minimum yield of 3 x 10(6) CD34(+) cells/kg was procured following a single apheresis procedure in 61% of the rhTPO and G-CSF-mobilized group versus 10% of G-CSF-mobilized patients (P =.001). In rhTPO and G-CSF mobilized patients, granulocyte (day 8 v 9, P =.0001) and platelet recovery (day 9 v 10, P =.07) were accelerated, and fewer erythrocyte (3 v 4, P =.02) and platelet (4 v 5, P =.02) transfusions were needed compared with G-CSF-mobilized patients. Peripheral blood platelet counts, following rhTPO and G-CSF, were increased by greater than 100% and the platelet content of PBPC products by 60% to 110% on the first and second days of aphereses (P <.0001) with the greatest effect seen with repeated dosing of rhTPO at 0.6 microgram/kg. rhTPO is safe and well tolerated as a mobilizing agent before PBPC collection. Mobilization with rhTPO and G-CSF, in comparison to a comparable, nonrandomized G-CSF-mobilized group of patients, decreases the number of apheresis procedures required, may accelerate hematopoietic recovery, and may reduce the number of transfusions required following high-dose chemotherapy for breast cancer.  (+info)

Immunohematological reference ranges for adult Ethiopians. (16/2217)

A cross-sectional survey was carried out with 485 healthy working adult Ethiopians who are participating in a cohort study on the progression of human immunodeficiency virus type 1 (HIV-1) infection to establish hematological reference ranges for adult HIV-negative Ethiopians. In addition, enumeration of absolute numbers and percentages of leukocyte subsets was performed for 142 randomly selected HIV-negative individuals. Immunological results were compared to those of 1,356 healthy HIV-negative Dutch blood donor controls. Immunohematological mean values, medians, and 95th percentile reference ranges were established. Mean values were as follows: leukocyte (WBC) counts, 6.1 x 10(9)/liter (both genders); erythrocyte counts, 5.1 x 10(12)/liter (males) and 4.5 x 10(12)/liter (females); hemoglobin, 16.1 (male) and 14.3 (female) g/dl; hematocrit, 48.3% (male) and 42.0% (female); platelets, 205 x 10(9)/liter (both genders); monocytes, 343/microl; granulocytes, 3, 057/microl; lymphocytes, 1,857/microl; CD4 T cells, 775/microl; CD8 T cells, 747/microl; CD4/CD8 T-cell ratio, 1.2; T cells, 1, 555/microl; B cells, 191/microl; and NK cells, 250/microl. The major conclusions follow. (i) The WBC and platelet values of healthy HIV-negative Ethiopians are lower than the adopted reference values of Ethiopia. (ii) The absolute CD4 T-cell counts of healthy HIV-negative Ethiopians are considerably lower than those of the Dutch controls, while the opposite is true for the absolute CD8 T-cell counts. This results in a significantly reduced CD4/CD8 T-cell ratio for healthy Ethiopians, compared to the ratio for Dutch controls.  (+info)