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PubMed2002

Neonatal alloimmune thrombocytopenia in the Irish population: a discrepancy between observed and expected cases.

AIMS: To estimate the rate of detection of neonatal alloimmune thrombocytopenia (NAITP) in the Irish population, to investigate clinical presentation and outcome in affected infants, and to determine the extent, if any, to which this condition is underdiagnosed at present. METHODS: Cases were collected in a retrospective fashion from a review of platelet serology laboratory records from January 1992 to December 2000. Clinical data were obtained from hospital records. Testing for maternal antiplatelet antibody was by one or more of the following: the platelet suspension immunofluorescence test, a commercial antigen capture enzyme linked immunosorbent assay (GTI-PakPlus), and the monoclonal antibody immobilisation of platelet antigens assay. Platelet antigen typing was by the polymerase chain reaction technique with sequence specific primers. RESULTS: Twenty seven serologically verified cases of NAITP were identified in 18 families. Maternal antibody to human platelet antigen 1a accounted for 25 of the 27 confirmed cases. Twenty one of 26 infants were born with severe thrombocytopenia. Nineteen of 27 infants had bleeding manifestations at birth. Petechiae and bruising were most commonly observed (n = 17). There were no documented cases of intracranial haemorrhage in this group but systematic cranial ultrasound was not performed. CONCLUSIONS: Screening studies in predominantly white populations have estimated the incidence of NAITP to be between 1 in 1000 and 1 in 2000 live births. With 50 000 births each year in Ireland, these results give a clinical detection rate for NAITP of just 1 case in 16 500 live births, strongly suggesting that NAITP is currently underdiagnosed. Antenatal screening to detect women at risk of having babies with NAITP is now scientifically feasible and should be considered.

Antigens, Human Platelet↗
PubMed2004

Platelet-leukocyte interaction and platelet activation in migraine: a link to ischemic stroke?

OBJECTIVES: Migraine has been identified as an independent risk factor for ischemic stroke. Both neurogenic inflammation and platelet activation have been linked to the pathophysiology of migraine. Increased platelet activation results in up-regulation of specific binding to leukocytes which promotes pro-inflammatory leukocyte secretion and their tethering to endothelium, a mechanism that has been demonstrated in stroke and which could provide a link to migraine. We aimed to determine whether platelet-leukocyte aggregation is increased in migraine patients outside an acute attack. METHODS: Seventy two patients with migraine according to IHS criteria were compared to a control group (n = 72). Whole blood flow cytometry was used to quantify the activation dependent P selectin on the platelet, and to assess the fraction of platelets bound to the different leukocyte subsets. RESULTS: Migraine patients showed significantly more platelet-leukocyte aggregates compared to the control subjects (p = 0.003). This effect was driven by an increased polymorphonuclear cell-platelet aggregation (p = 0.003) whereas platelet aggregation with monocytes and lymphocytes was not. Platelet activation was also increased (p = 0.001). CONCLUSIONS: In migraine pro-inflammatory platelet adhesion to leukocytes occurs during the headache free interval similar to that seen in acute coronary and cerebrovascular syndromes. This may suggest a link between migraine and stroke on a cellular level.

Acute Disease↗
PubMed2000

Separate pathways for cellular uptake of ferric and ferrous iron.

Separate pathways for transport of nontransferrin ferric and ferrous iron into tissue cultured cells were demonstrated. Neither the ferric nor ferrous pathway was shared with either zinc or copper. Manganese shared the ferrous pathway but had no effect on cellular uptake of ferric iron. We postulate that ferric iron was transported into cells via beta(3)-integrin and mobilferrin (IMP), whereas ferrous iron uptake was facilitated by divalent metal transporter-1 (DMT-1; Nramp-2). These conclusions were documented by competitive inhibition studies, utilization of a beta(3)-integrin antibody that blocked uptake of ferric but not ferrous iron, development of an anti-DMT-1 antibody that blocked ferrous iron and manganese uptake but not ferric iron, transfection of DMT-1 DNA into tissue culture cells that showed enhanced uptake of ferrous iron and manganese but neither ferric iron nor zinc, hepatic metal concentrations in mk mice showing decreased iron and manganese but not zinc or copper, and data showing that the addition of reducing agents to tissue culture media altered iron binding to proteins of the IMP and DMT-1 pathways. Although these experiments show ferric and ferrous iron can enter cells via different pathways, they do not indicate which pathway is dominant in humans.

Amino Acid Substitution↗
PubMed2001

Effects of luminal shear stress on cerebral arteries and arterioles.

The effect of luminal shear stress was studied in cerebral arteries and arterioles. Middle cerebral arteries (MCA) and penetrating arterioles (PA) were isolated from male Long-Evans rats, mounted in a tissue bath, and pressurized. After the development of spontaneous tone, inside diameters were 186 +/- 5 microm (n = 28) for MCA and 65 +/- 3 microm (n = 37) for PA. MCA and PA constricted approximately 20% with increasing flow. Flow-induced constriction persisted in MCA and PA after removal of the endothelium. After removal of the endothelium, the luminal application of a polypeptide containing the Arg-Gly-Asp amino acid sequence (inhibitor of integrin attachment) abolished the flow-induced constriction. Similarly, an antibody specific for the beta(3)-chain of the integrin complex significantly inhibited the flow-induced constriction. The shear stress-induced constriction was accompanied by an increase in vascular smooth muscle Ca(2+). For example, a shear stress of 20 dyn/cm(2) constricted MCA 8% (n = 5) and increased Ca(2+) from 209 +/- 17 to 262 +/- 29 nM (n = 5). We conclude that isolated cerebral arteries and arterioles from the rat constrict to increased shear stress. Because the endothelium is not necessary for the response, the shear forces must be transmitted across the endothelium, presumably by the cytoskeletal matrix, to elicit constriction. Integrins containing the beta(3)-chain are involved with the shear stress-induced constrictions.

Animals↗
PubMed2005

Role of phosphatidylinositol 3-kinase-gamma in mediating lung neutrophil sequestration and vascular injury induced by E. coli sepsis.

We addressed the in vivo role of phosphatidylinositol 3-kinase-gamma (PI3K-gamma) in signaling the sequestration of polymorphonuclear leukocytes (PMNs) in lungs and in the mechanism of inflammatory lung vascular injury. We studied mice with deletion of the p110 catalytic subunit of PI3K-gamma (PI3K-gamma(-/-) mice). We measured lung tissue PMN sequestration, microvascular permeability, and edema formation after bacteremia induced by intraperitoneal Escherichia coli challenge. PMN infiltration into the lung interstitium in PI3K-gamma(-/-) mice as assessed morphometrically was increased 100% over that in control mice within 1 h after bacterial challenge. PI3K-gamma(-/-) mice also developed a greater increase in lung microvascular permeability after E. coli challenge, resulting in edema formation. The augmented lung tissue PMN sequestration in PI3K-gamma(-/-) mice was associated with increased expression of the PMN adhesive proteins CD47 and beta(3)-integrins. We observed increased association of CD47 and beta(3)-integrins with the extracellular matrix protein vitronectin in lungs of PI3K-gamma(-/-) mice after E. coli challenge. PMNs from these mice also showed increased beta(3)-integrin expression and augmented beta(3)-integrin-dependent PMN adhesion to vitronectin. These results point to a key role of PMN PI3K-gamma in negatively regulating CD47 and beta(3)-integrin expression in gram-negative sepsis. PI3K-gamma activation in PMNs induced by E. coli may modulate the extent of lung tissue PMN sequestration secondary to CD47 and beta(3)-integrin expression. Therefore, the level of PI3K-gamma activation may be an important determinant of PMN-dependent lung vascular injury.

Animals↗
PubMed2006

Evidence that calcineurin is required for the genesis of bone-resorbing osteoclasts.

Here, we demonstrate that the Ca(2+)/calmodulin-sensitive phosphatase calcineurin is a necessary downstream mediator for osteoclast differentiation. Using quantitative PCR, we detected the calcineurin isoforms Aalpha, Abeta, Agamma (catalytic), and B1 (regulatory) in osteoclast precursor RAW-C3 cells. We found that, although the expression of these isoforms remained relatively unchanged during osteoclast differentiation, there was a profound increase in the expression of their primary substrate for calcineurin, nuclear factor of activated T cells (NFAT)c1. For gain-of-function studies, we incubated osteoclast precursors for 10 min with a calcineurin fusion protein (TAT-calcineurin Aalpha); this resulted in its receptorless influx into >90% of the precursor cells. A marked increase in the expression of the osteoclast differentiation markers tartrate-resistant acid phosphatase (TRAP) and integrin beta(3) followed. In addition, the expression of NFATc1, as well as the alternative substrate for calcineurin, IkappaBalpha, was significantly enhanced. Likewise, transfection with constitutively active NFAT resulted in an increased expression of both TRAP and integrin beta(3). In parallel loss-of-function studies, transfection with dominant-negative NFAT not only inhibited osteoclast formation but also reversed the induction of NFATc1, TRAP, and integrin beta(3) by TAT-calcineurin Aalpha. The expression of these markers was also inhibited by calcineurin Aalpha U1 small nuclear RNA, which significantly reduced calcineurin Aalpha mRNA and protein expression. Consistent with these observations, we observed a reduction in osteoclastogenesis in calcineurin Aalpha(-/-) cells and in osteoclast precursors treated with the calcineurin inhibitors cyclosporin A and FK506. Together, the gain- and loss-of-function experiments establish that calcineurin Aalpha is necessary for osteoclast formation from its precursor and that this occurs via an NFATc1-dependent mechanism.

Acid Phosphatase↗
PubMed2006

Protein disulfide isomerase expression is related to the invasive properties of malignant glioma.

By serial transplantation of human glioblastoma biopsies into the brain of immunodeficient nude rats, two different tumor phenotypes were obtained. Initially, the transplanted xenografts displayed a highly invasive phenotype that showed no signs of angiogenesis. By serial transplantation in animals, the tumors changed to a less invasive, predominantly angiogenic phenotype. To identify novel proteins related to the invasive phenotype, the xenografts were analyzed using a global proteomics approach. One of the identified proteins was protein disulfide isomerase (PDI) A6 precursor. PDI is a chaperone protein that mediates integrin-dependent cell adhesion. It is both present in the cytosol and at the cell surface. We show that PDI is strongly expressed on invasive glioma cells, in both xenografts and at the invasive front of human glioblastomas. Using an in vitro migration assay, we also show that PDI is expressed on migrating glioma cells. To determine the functional significance of PDI in cell migration, we tested the effect of a PDI inhibitor, bacitracin, and a PDI monoclonal antibody on glioma cell migration and invasion in vitro. Both tumor spheroids derived from human glioblastoma xenografts in nude rat brain and cell line spheroids were used. The PDI antibody, as well as bacitracin, inhibited tumor cell migration and invasion. The anti-invasive effect of bacitracin was reversible after withdrawal of the inhibitor, indicating a specific, nontoxic effect. In conclusion, using a global proteomics approach, PDI was identified to play an important role in glioma cell invasion, and its action was effectively inhibited by bacitracin.

Animals↗
PubMed1998

Management of fetal and neonatal alloimmune thrombocytopenia.

Fetal and neonatal thrombocytopenia can be induced by a maternal alloimmunization against fetal platelet antigens. Alloimmune thrombocytopenia occurs with an incidence of 1/1,000 livebirths and may present either with evidence of damage from a prenatal hemorrhage such as porencephaly or intrauterine death, or with active life-threatening bleeding during the neonatal period. It is due to the destruction of fetal platelets by alloantibodies reacting on specific antigenic sites. In Caucasians, the human platelet antigen 1a (HPA-1a) is the most frequently involved in alloimmune thrombocytopenias, accounting for 80-90% of the cases. Anti-HPA-5b is responsible for a further 5-15% of the cases. This article reviews the clinical aspects, the biological diagnosis and the management, including prenatal sampling and maternal therapy.

Antigens, Human Platelet↗
PubMed1999

An international trial demonstrates suitability of a newly developed whole-blood ELISA kit for multicentre platelet HPA-1 phenotyping.

BACKGROUND: Neonatal alloimmune thrombocytopenia (NAIT) is in most cases due to pregnant women with HPA-1b platelet phenotype producing antibodies to HPA-1a platelets of the fetus, which may lead to intracranial haemorrhage with subsequent death or life-long morbidity. The availability of sensitive, reliable, straightforward, and inexpensive assays would enable large-scale screening in pregnancy and may help avoid NAIT. METHODS: A recently developed enzyme-linked immunosorbent assay (ELISA) was produced in kit form incorporating modified reagents and enabling distribution to 21 international Platelet Immunology and Blood Centres (see Acknowledgements). The kits were assessed using anticoagulated whole-blood samples stored up to 10 weeks at 4 degrees C. Each centre tested its own blood samples most of which had been previously typed by established assays. RESULTS: Of the 152 samples that were tested, all 31 HPA-1b phenotypes were correctly identified by the kit. The respective mean +/- standard deviation of the specific absorbances of HPA-1b and HPA-1a samples were: 0.52+/-0.15 and 0.12+/-0.06 (p<0.0005). In addition, the modified ELISA showed 100% concordance with PCR-SSP in the phenotyping of 93 donors. Finally, a comparison between freshly prepared and stored kits showed that the kit was stable for at least 2 years at 4 degrees C. CONCLUSIONS: The international trial showed that the modified whole-blood ELISA kit is very well suited for wide-scale screening in pregnancy. Moreover, the ELISA kit could be used for large-scale phenotyping of blood donors, with HPA-1b-typed individuals getting invited to become apheresis platelet donors for patients with NAIT.

Adult↗
PubMed1999

Allele frequencies of human platelet antigen 1, 2, 3, and 5 systems in patients with chronic refractory autoimmune thrombocytopenia and in normal persons.

BACKGROUND AND OBJECTIVES: Chronic refractory autoimmune thrombocytopenic purpura (AITP) is an autoimmune disorder due to autoantibodies against platelet glycoproteins (GP). Human platelet alloantigenic (HPA) systems are distributed to different platelet GPs. We carried out genotyping of diallelic HPA-1, -2, -3, and -5 systems to clarify potential associations between HPA alleles and the development of chronic refractory AITP. PATIENTS AND METHODS: DNA was isolated from 33 unrelated German patients with chronic refractory AITP and from 80 randomly selected German blood donors to determine the phenotype and allele frequencies for the HPA-1, -2, -3, and -5 systems. Fragments carrying the polymorphic sequences corresponding to those alleles were amplified by the polymerase chain reaction and further characterized by restriction analysis. RESULTS: Whereas HPA-1, -3, and -5 allele frequencies were identical in 33 patients with chronic refractory AITP and in controls, HPA-2 allele frequencies showed a statistically significant difference (p = 0.017). In our group of patients, the HPA-2a allele frequency was 100%, but HPA-2b was not seen. In contrast, the allele frequency of HPA-2a in the control group was 92% (n = 147), and in HPA-2b it was 8% (n = 13). CONCLUSION: This study suggests an association between the HPA-2a allele and chronic refractory AITP. The HPA-2a allele may be involved in the formation of an AITP-specific autoepitope.

Adult↗
PubMed2003

Mixed chimerism of erythro- and megakaryopoiesis following allogeneic bone marrow transplantation.

Until now, studies on mixed chimerism (MCh) after allogeneic bone marrow transplantation (BMT) have predominantly focused on the B- and T-lymphocyte population, but not on distinct myeloid cell lineages like nucleated erythroid precursors and megakaryocytes. To evaluate the lineage-restricted MCh more explicitly in 10 patients with chronic myelogenous leukemia (CML), a quantitative analysis was performed on bone marrow biopsies following a sex-mismatched host/donor constellation. Techniques included immunophenotyping (antiglycophorin C, CD61) for the identification of erythro- and megakaryopoiesis and a simultaneously conducted genotyping with x- and y-chromosome-specific DNA probes. Normal bone marrow and specimens taken before BMT served as controls. Contrasting a total gender-dependent sex-typing in the latter samples in the early and late posttransplant period (up to 586 days), 3-9% erythroid precursors and about 16% megakaryocytes revealed a host-type origin. This significantly higher number of host megakaryocytes is explained by their polyploidy generating an increased probability to detect positive signals at a certain section level of the corresponding biopsies. A striking conversion of MCh to a recipient cell type was found in leukemic relapse with a more than 90% host-derived erythroid and megakaryocytic cell population in 4 patients approximately 643 days after BMT.

Adult↗
PubMed2004

Activation of resistance arteries with endothelin-1: from vasoconstriction to functional adaptation and remodeling.

Remodeling of resistance arteries is a key feature in hypertension. We studied the transition of vasoconstriction to remodeling in isolated rat skeletal muscle arterioles. Arterioles activated with 10 nM endothelin-1 showed functional adaptation when kept at low distension in a wire myograph setup, where contractile properties shifted towards a smaller lumen diameter after 1 day. Pressurized arteries kept in organoid culture showed physical inward remodeling after 3-day activation with 10 nM endothelin-1, characterized by a reduction in relaxed diameter without a change in the wall cross-sectional area (eutrophic remodeling). The relaxed lumen diameter (at 60 mm Hg) decreased from 169 +/- 5 (day 0) to 155 +/- 4 microm (day 3). An antibody directed to the beta(3)-integrin subunit (but not one directed to the beta(1)-integrin subunit) enhanced remodeling, from a reduction in relaxed diameter at 60 mm Hg of 15 +/- 2.4 to 22 +/- 1.8 microm (both on day 3). Collagen gel contraction experiments showed that the antibody directed to the beta(3)-integrin subunit enhanced the compaction of collagen by smooth muscle cells, from 83 +/- 1.5 to 68 +/- 1.5% of the initial gel diameter. In conclusion, these data show that inward eutrophic remodeling is a response to sustained contraction, which may involve collagen reorganization through beta(3)-integrins.

Adaptation, Physiological↗
PubMed1997

Characteristics of a cell line established from a case of acute megakaryoblastic leukemia.

Acute megakaryoblastic leukemia is uncommon and comprises about 5% of acute nonlymphoid leukemias in the French-American-British classification. Cell lines from such leukemias are relatively rare with only about 8 reported in the literature. We established a cell line from a case of acute megakaryoblastic leukemia arising in a 2-year-old child. Surface marker studies of the cells confirmed their megakaryoblastic nature, with 54% of the cells being CD61 positive and peroxidase and esterase negative. The cells had a doubling time of 72 h. Emperipolesis (a phenomenon in which a cell, usually a lymphocyte or neutrophil, enters another cell, moves about and leaves without undergoing phagocytosis) of one blast into another, larger one, was occasionally seen, and a review of the original bone marrow specimen also showed emperipolesis of neutrophils into the megakaryoblasts. The cells responded to interleukin 3 and were inhibited with all-trans-retinoic acid. The karyotype of the cells was the 46,XX,-16 with a marker chromosome. The marker chromosome is possibly chromosome 16 with a small segment of a chromosome translocated to the terminal portion of chromosome 16.

Antigens, CD↗
PubMed1992

Neonatal alloimmune thrombocytopenia due to HLA-A2 antibody.

A male, full-term baby with thrombocytopenia was born by a G3P2A1 mother who was not associated with autoimmune disease. Platelet antibody screening was positive by using lymphocytotoxicity test, platelet suspension immunofluorescence test and solid-phase red cell adherence test. The identified HLA antibody was of A2 specificity. It was confirmed by testing the mother's and the baby's sera against the lymphocytes and platelets of 10 HLA-A2-positive donors. The possibility of platelet-specific antibody as the cause of neonatal alloimmune thrombocytopenia was ruled out by testing against platelets of 10 HLA-A2-negative donors and the known platelet-specific antigens utilizing immobilized, purified platelet glycoprotein as targets. The mother's serum reacted strongly with both the father's and the baby's platelets and lymphocytes. This neonatal thrombocytopenia was most likely due to the maternal HLA antibody, which was induced by her antecedent gestations.

Antigens, Human Platelet↗
PubMed1992

Alloimmune thrombocytopenia: in utero treatment by high doses of intravenous gamma globulins.

The authors report successful in utero treatment by high doses of intravenous gamma globulins in a case of neonatal alloimmune thrombocytopenia. Early diagnosis allows an appropriate management: fetal blood sampling as early as 20 weeks of gestation; in case of fetal thrombocytopenia, treatment by intravenous gamma globulin (1.0 g/kg/b.w.) each week during 8 weeks or more; ultrasound screening of in utero hemorrhage, particularly intracranial hemorrhage; fetal blood sampling before delivery at term and in utero transfusion of platelet antigen negative in case of persistence of fetal thrombocytopenia.

Adult↗
PubMedDate not supplied

Successful treatment of fetal cardiac arrest by left ventricular exchange transfusion.

A 36-year-old pregnant woman with anti-HPA1a antibodies underwent six fetal platelet concentrate transfusions. During the second, at 28 weeks' gestation, fetal asystole occurred in association with a post-transfusion platelet count of 813 x 10(9)/l. Asystole was reversed by an intracardiac partial exchange transfusion of normal saline for fetal blood, simultaneously reducing fetal plasma viscosity and enabling re-commencement of the fetal circulation.

Adult↗