Functional analysis of single amino-acid mutations in the thrombopoietin-receptor Mpl underlying congenital amegakaryocytic thrombocytopenia.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare disorder that presents with severe thrombocytopenia and absence of megakaryocytes in the bone marrow. The disease may develop into bone marrow aplasia. Genetic defects in the gene encoding the thrombopoietin (Tpo) receptor, MPL, are the cause of this disease.

C-type lectin-like molecule-1: a novel myeloid cell surface marker associated with acute myeloid leukemia.

Acute myeloid leukemia (AML) has a poor prognosis due to treatment-resistant relapses. A humanized anti-CD33 antibody (Mylotarg) showed a limited response rate in relapsed AML. To discover novel AML antibody targets, we selected a panel of single chain Fv fragments using phage display technology combined with flow cytometry on AML tumor samples.

A novel helper phage that improves phage display selection efficiency by preventing the amplification of phages without recombinant protein.

Phage display is a widely used technology for the isolation of peptides and proteins with specific binding properties from large libraries of these molecules. A drawback of the common phagemid/helper phage systems is the high infective background of phages that do not display the protein of interest, but are propagated due to non-specific binding to selection targets. This and the enhanced growth rates of bacteria harboring aberrant phagemids not expressing recombinant proteins leads to a serious decrease in selection efficiency.

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.

The potential role of thrombopoietin in idiopathic thrombocytopenic purpura.

Thrombopoietin (TPO) plays a central role in the pathogenesis of idiopathic thrombocytopenic purpura (ITP), as it does in other immune-mediated thrombocytopenias. Because TPO is bound and internalized by platelets, it is destroyed together with platelets at an accelerated rate in the macrophage system. Because the spleen acts as a TPO sink, compensation of the decreased platelet count by an increased production in the bone marrow is insufficient.

[From gene to disease; from a thrombopoietin receptor gene defect to congenital amegakaryocytic thrombocytopenia].

Congenital amegakaryocytic thrombocytopenia (CAMT) is an uncommon cause of thrombocytopenia in children. CAMT is characterised by an isolated thrombocytopenia and the near absence of megakaryocytes in the bone marrow. The gene involved in the development of CAMT has recently been described.

Influence of medium components on ex vivo megakaryocyte expansion.

Reinfusion of ex vivo-expanded autologous megakaryocytes together with a stem cell transplantation may be useful to prevent or reduce the period of chemotherapy-induced thrombocytopenia. In this study, we analyzed several serum-containing and serum-free media to identify the most suitable medium for megakaryocyte expansion. Moreover, two thrombopoietin (Tpo)-mimetic peptides were tested to evaluate whether they could replace Tpo in an expansion protocol.

Differences in megakaryocyte expansion potential between CD34(+) stem cells derived from cord blood, peripheral blood, and bone marrow from adults and children.

Objective: Reinfusion of ex vivo expanded autologous megakaryocytes together with stem cell transplantation may be useful to prevent or reduce the period of chemotherapy-induced thrombocytopenia. We compared the megakaryocyte expansion potential of CD34(+) stem cells derived from different sources: cord blood (CB), peripheral blood (PB), bone marrow from adults (ABM), and bone marrow from children (ChBM). Three different growth factor combinations were tested to identify the best combination for each of the sources.

Mutations in the thrombopoietin receptor, Mpl, in children with congenital amegakaryocytic thrombocytopenia.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a rare disorder of undefined aetiology. The disease presents with severe thrombocytopenia and absence of megakaryocytes in the bone marrow. Furthermore, CAMT patients may develop bone marrow aplasia.

A combination of megakaryocyte growth and development factor and interleukin-1 is sufficient to culture large numbers of megakaryocytic progenitors and megakaryocytes for transfusion purposes.

Chemotherapy-induced thrombocytopenia is a major risk factor in cancer treatment. The transfusion of autologous ex vivo expanded megakaryocytes could be a new therapy to shorten the period of thrombocytopenia. Therefore we investigated, in a liquid culture system, the effect of various cytokine combinations composed of pegylated megakaryocyte growth and development factor (PEG-rHuMGDF), interleukin-1 (IL-1), IL-3, IL-6, IL-11 and stem cell factor (SCF) on the proliferation and differentiation of CD34+ cells, in order to define the most optimal and minimum levels of cytokine combinations for megakaryocyte expansion.

Silverfish protein in house dust in relation to mite and total arthropod level.

Two assays have been developed to measure arthropod levels in house dust. The first assay measures silverfish antigens. The second assay measures invertebrate tropomyosin and gives a global assessment of the level of arthropod-derived material.

IgE antibodies reactive with silverfish, cockroach and chironomid are frequently found in mite-positive allergic patients.

Approximately 30% of the house dust mite allergic patients in The Netherlands have IgE antibodies reactive with silverfish, cockroach and/or chironomid. In allergic patients without IgE antibodies against Dermatophagoides pteronyssinus less than 5% have IgE antibodies reactive with these insects. By means of RAST inhibition studies it is shown that cross-reactivity exists between D.