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Masja de Haas

Publications and source records attributed to Masja de Haas.

13 recordsLinked to original sources
PubMed2006

FcRn: an IgG receptor on phagocytes with a novel role in phagocytosis.

Here, we report that the MHC class I-related neonatal Fc receptor (FcRn) is expressed within azurophilic and specific granules of neutrophils and relocates to phagolysosomes on phagocytosis of IgG-opsonized bacteria. We found FcRn to enhance phagocytosis in a pH-dependent manner which was independent of IgG recycling. IgG-opsonized bacteria were inefficiently phagocytosed by neutrophils from beta2M knock-out or FcRn alpha-chain knock-out mice, which both lack expression of FcRn. Similarly, low phagocytic activity was also observed with mutated IgG (H435A), which is incapable of binding to FcRn, while retaining normal binding to classical leukocyte Fcgamma receptors. Finally, a TAT peptide representing intracellular endocytosis and transport motifs within FcRn strongly inhibited IgG-mediated phagocytosis. These findings support a novel concept in which FcRn fulfills a major role in IgG-mediated phagocytosis.

Animals↗
PubMed2006

Evaluation of prenatal RHD typing strategies on cell-free fetal DNA from maternal plasma.

BACKGROUND: The discovery of cell-free fetal DNA in maternal plasma led to the development of assays to predict the fetal D status with RHD-specific sequences. Few assays are designed in such a way that the fetus can be typed in RHDpsi mothers and that RHDpsi fetuses are correctly typed. Owing to the limited knowledge about the mechanism responsible for the presence of fetal DNA in maternal plasma, precautions in developing prenatal genotyping strategies must be made. STUDY DESIGN AND METHODS: Real-time quantitative (RQ)-polymerase chain reaction (PCR) assays were developed for prenatal diagnostic use with cell-free fetal DNA from maternal plasma. An RQ-PCR assay on RHD exon 5 (amplicon 361 bp), negative on RHDpsi, was developed with genomic DNA and evaluated with cell-free fetal DNA. A previously published RHD exon 5 RQ-PCR (amplicon 82 bp) was duplexed with an in-house developed RHD exon 7 RQ-PCR and evaluated with cell-free fetal DNA from pregnant D-RHDpsi+ women. RESULTS: The RHD exon 5 361 bp assay showed on cell-free plasma DNA from D- women carrying a D+ fetus, low amplification levels, resulting in high Ct values and false-negative results. Owing to fragmentation of cell-free plasma DNA, too few DNA stretches of sufficient length (> 360 bp) are present. The RHD exon 5 82 bp and exon 7 RQ-PCR duplex was evaluated with RHDpsi+ cell-free plasma DNA and showed complete specificity and maximal sensitivity. CONCLUSION: Assays designed for prenatal genotyping should be developed and evaluated on cell-free plasma DNA. Prenatal RHD typing is accurate with the RHD exon 5 82 bp and exon 7 duplex strategy.

Blood Grouping and Crossmatching↗
PubMed2005

Juvenile cyclic amegakaryocytic thrombocytopenia: a novel entity.

Cyclic thrombocytopenia is a rare disorder described in adults, characterized by periodic platelet count fluctuations of unknown etiology. The authors describe a boy with cyclic changes in platelet counts ranging from 2 x 10(9)/L to 224 x 10(9)/L with a periodicity of 25 days. Since birth, the patient had periods of bruising. Platelet counts were periodically low during these periods. Thrombopoietin plasma levels oscillated inversely with the platelet count, whereas glycocalicin levels oscillated in phase with the platelets. No oscillation was seen in neutrophil and reticulocyte numbers. The bone marrow showed periodic reduction in megakaryocyte counts. In an in vitro megakaryocytopoiesis assay, the patient's CD34+ cells showed megakaryocyte formation, although to a lower level than controls. Addition of patient plasma, collected during the rise in platelet numbers, to cultures with normal bone marrow-derived CD34+ cells caused an increase in the development of CD41+ megakaryoblasts. Because the periods with bruising had existed since birth, apparently this is a form of congenital cyclic thrombocytopenia. The underlying mechanism of the cyclic thrombocytopenia in this patient is not yet clear, and until now, no therapy has been found for this patient. However, platelet transfusions have resulted in cessation of bleeding during thrombocytopenic periods.

Antigens, CD34↗
PubMed2005

Rapid genotyping of blood group antigens by multiplex polymerase chain reaction and DNA microarray hybridization.

BACKGROUND: In the Netherlands, 500,000 blood donors are active. Blood of all donors is currently typed serologically for ABO, the Rh phenotype, and K. Only a subset of donors is typed twice for a larger set of red cell (RBC) and/or platelet (PLT) antigens. To increase the direct availability of typed RBCs and PLTs, a high-throughput technique is being developed to genotype the whole donor cohort for all clinically relevant RBC and PLT antigens. STUDY DESIGN AND METHODS: A multiplex polymerase chain reaction was developed to both amplify and fluorescently label 19 gene fragments of RBC and PLT antigens in one reaction. To test the setup of the genotyping method by microarray, a pilot study with human PLT antigen (HPA)-typed donor samples was performed. On each slide, 12 arrays are present containing 20 probes per PLT antigen system (28 for HPA-3). The allele-specific oligohybridization method was used to discriminate between two different alleles. RESULTS: Two blinded panels encompassing 94 donors were genotyped for HPA-1 through -5 and -15; no discrepancies were found compared to their serologic typing (HPA-1, -2, -3, -4, and -5) and genotyping (HPA-15; TaqMan, Applied Biosystems). CONCLUSION: This study shows that the HPA microarray provides a reliable and fast genotyping procedure. With further development an automated throughput for complete typing of large donor cohorts can be obtained.

Antigens, Human Platelet↗
PubMed2004

Clinical applications of cell-free fetal DNA from maternal plasma.

OBJECTIVE: To describe our clinical experience with detection and analysis of cell-free fetal DNA derived from maternal plasma for prenatal sexing and fetal rhesus-D typing. METHODS: Real-time quantitative polymerase chain reactions (PCRs) of rhesus-D sequences and the SRY gene were validated and offered to patients with an enhanced risk for sex-linked fetal pathology and patients with rhesus-D antibodies. RESULTS: In the validation group, 72 samples were analyzed. Sensitivity of the rhesus-D real-time quantitative PCR in maternal plasma was 100% (95% confidence interval [CI]91.8%, 100%) and specificity was 96.6% (95% CI 82.2%, 99.9%). Sensitivity of the SRY real-time quantitative PCR was 97.2% (95% CI 85.5%, 99.9%), and specificity was 100% (95% CI 88.1%, 100%). The technique was used successfully in a clinical setting in 24 women. Overall, invasive tests were avoided in 41.7% of these patients. CONCLUSION: Detection of cell-free fetal DNA from maternal plasma is a reliable technique that can substantially reduce invasive prenatal tests.

DNA↗
PubMed2004

Platelet count, previous infection and FCGR2B genotype predict development of chronic disease in newly diagnosed idiopathic thrombocytopenia in childhood: results of a prospective study.

About 25-30% of children with acute idiopathic thrombocytopenia (ITP) develop chronic disease. It is not well known which patient characteristics influence the course of the ITP. A prospective study in 60 children with newly diagnosed ITP was performed. The aim of the study was to identify patient characteristics at the onset of thrombocytopenia that predicts the progression to chronic ITP. Clinical data and blood samples were collected at several time points during the first 6 months of the disease. Variables predicting chronic disease, as calculated in a multivariate logistic regression analysis, were a platelet count >10 x 10(9)/l at the onset [odds ratio (OR) 1.1, 95% confidence interval (CI) 1.01-1.14], the absence of infection shortly before the onset of the disease (OR 4.8, CI 1.16-19.57) and FGR2B-232I/T genotype (OR 7.9, CI 0.96-65.27). The latter may point at an immune-modulating role of Fc gamma RIIb in ITP. Although only three patients had serious bleeds, 35 patients received immune-modulating treatment for low platelet counts only. Seventeen patients were treated with intravenous immunoglobulin (IVIG) and 18 patients received corticosteroids. Patient variables did not differ between these treatment groups. However, patients receiving IVIG had significantly lower risk for chronic disease.

Adolescent↗
PubMed2003

Prenatal typing of Rh and Kell blood group system antigens: the edge of a watershed.

Knowledge of the molecular basis of the blood group systems has enabled the development of assays for blood group genotyping. At this time, polymerase chain reaction (PCR)-based assays validated on fetal material obtained by invasive means (chorionic villus sampling or amniocentesis) are available for all clinically relevant fetal blood groups, However, only Rh typing (D, C, c, E, and e) and K1 genotyping assays are discussed in this review. Importantly, one must remember that results of genotyping assays will not always be concordant with serological typing. Thus, the RhD genotyping assays have to be modified in response to increased understanding of the molecular biology of this blood group system. RhD typing assays should produce negative results when tested on the black RhD-negative RHD alleles, RHDpsi and r's. PCR-based assays can be used to determine paternal zygosity. For RhD zygosity testing, the real-time quantitative PCR approach and the direct detection of the hybrid Rhesus box, which is the result of the deletion of the RHD gene are available. Recently, methods for noninvasive prenatal genotyping have been investigated. The use of fetal cells circulating in the maternal circulation has been explored; however, the scarcity of circulating fetal cells has limited the use of this approach. More promising are the results obtained with RhD typing assays with cell-free fetal DNA, which is present in the maternal circulation in a concentration of 25 genomic equivalents per milliliter of maternal blood in early pregnancy increasing to 100 copies per milliliter in the third trimester, which is cleared from the circulation within a few hours of delivery. The positive predictive value of this approach is virtually 100%, but false-negative results are (infrequently) encountered. Therefore, this assay can at present only be used for screening of RhD-negative women to make the use of antenatal prophylaxis more targeted and hence more cost-effective. For the clinical management of the pregnancies of alloimmunized women, the development of a control for the presence and the amplification of fetal DNA is needed, which is at present only available in male pregnancies. Assays for the genotyping of the other Rh antigens or Kell antigens with cell-free fetal DNA have not yet been described.

Blood Group Antigens↗
PubMed2002

Low Fcgamma receptor III and high granulocyte colony-stimulating factor serum levels correlate with the risk of infection in neutropenia due to Felty's syndrome or systemic lupus erythematosus.

PURPOSE: To determine whether serum levels of soluble Fcgamma receptor III and granulocyte colony-stimulating factor (G-CSF) are associated with the risk of infection in patients with neutropenia due to Felty's syndrome or systemic lupus erythematosus. SUBJECTS AND METHODS: Serum levels of G-CSF and soluble Fcgamma receptor III were measured by enzyme-linked immunosorbent assays in 13 patients with neutropenia due to Felty's syndrome, 10 patients with neutropenia due to systemic lupus erythematosus, and 41 controls with normal leukocyte counts (25 with systemic lupus erythematosus, 16 with rheumatoid arthritis). We calculated the area under the receiver operating characteristic (ROC) curves for the absolute neutrophil count, soluble Fcgamma receptor III levels, and G-CSF levels. RESULTS: Nine of the neutropenic patients (7 with Felty's syndrome, 2 with lupus) had one or more infections within 3 months before and after blood samples were obtained. Absolute neutrophil counts were similar in neutropenic patients who did or did not have infections. However, the median level of soluble Fcgamma receptor III (63 vs. 126 arbitrary units, P = 0.005) was significantly lower among patients who developed infections, whereas the median level of G-CSF (90.9 vs. 53.3 pg/mL, P = 0.04) was significantly higher compared with patients without infections. The area under the ROC curve was 0.58 (P = 0.49) for the absolute neutrophil count, 0.84 (P = 0.007) for soluble Fcgamma receptor III levels, and 0.73 (P = 0.03) for G-CSF levels. CONCLUSION: In patients with chronic neutropenia due to rheumatic diseases, low soluble Fcgamma receptor III levels and elevated G-CSF levels are better indicators of the risk of infection than is the neutrophil count.

Adult↗
PubMed2002

CD antigens 2002.

Explore the source record for details and available documents.

Antibodies, Monoclonal↗
PubMed2002

Three parameters, plasma thrombopoietin levels, plasma glycocalicin levels and megakaryocyte culture, distinguish between different causes of congenital thrombocytopenia.

Fourteen children with congenital thrombocytopenia were analysed in order to unravel the mechanisms underlying their thrombocytopenia and to evaluate the value of new laboratory tests, namely measurement of plasma thrombopoietin (Tpo) and glycocalicin (GC) levels and analysis of megakaryocytopoiesis in vitro. Three groups of patients were included. The first group (n = 6) was diagnosed with congenital amegakaryocytic thrombocytopenia. They had no megakaryocytes in the bone marrow, three out of four patients showed no megakaryocyte formation in vitro, and all had high Tpo and low GC levels. Mutations in the thrombopoietin receptor gene, c-mpl, were the cause. The second group of patients (n = 3) had normal Tpo and severely decreased GC levels. In bone marrow, normal to increased numbers of atypical, dysmature megakaryocytes were present. In vitro megakaryocyte formation was quantitatively normal. A defect in final megakaryocyte maturation and subsequent (pro-)platelets may be the cause of the thrombocytopenia. The patients in the third group (n = 5) had Wiskott-Aldrich syndrome (WAS). They had normal Tpo and GC levels and normal megakaryocyte formation both in vivo and in vitro. This corresponded with the generally accepted hypothesis that thrombocytopenia in WAS is due to increased platelet turnover. In conclusion, different causes of congenital thrombocytopenia can be distinguished using three parameters: Tpo and GC plasma levels and in vitro analysis of megakaryocytopoiesis. Therefore, these parameters may be helpful in early diagnosis of different forms of congenital thrombocytopenia.

Biomarkers↗
PubMed2002

Report on the Fourth International Granulocyte Immunology Workshop: progress toward quality assessment.

BACKGROUND: A formal quality assurance (QA) scheme has been established to facilitate proficiency testing for granulocyte antibodies and antigens. STUDY DESIGN AND METHODS: Fifteen laboratories participated in the Fourth International Granulocyte Immunology Workshop. The main objective of the workshop was to establish a formal QA scheme for granulocyte serology and molecular typing methods. A secondary objective was to determine the relative sensitivities of the granulocyte immunofluorescence test, granulocyte agglutination test, and MoAb immobilization assays using defined antisera and protocols. RESULTS: Laboratories scored between 16.7 and 100 percent (mean, 57.5%) of the maximum available in the serologic part of this QA exercise. There were particular problems in detecting granulocyte-specific human neutrophil antigen-1 (HNA-1a) IgM antibodies and HNA-2a antibodies in the presence of HNA-1b antibodies. The granulocyte immunofluorescence test was more sensitive than the granulocyte agglutination test in titration studies, but the latter method more readily identified the presence of HNA-3a antibodies. HNA genotyping was generally well performed, with nine laboratories obtaining 100-percent correct results for HNA-1a, HNA-1b, and HNA-1c. CONCLUSIONS: There is a need to standardize the detection of granulocyte-specific antibodies. Laboratories with good performance tended to use two methods for detecting granulocyte-specific antibodies and an HNA-typed panel of granulocytes. The use of a method for elucidating mixtures of granulocyte- and lymphocyte-reactive antibodies (e.g., MoAb immobilization assay) and the use of methods for detecting both cytotoxic and noncytotoxic HLA class I antibodies were also associated with a higher than average performance.

Agglutination Tests↗