Precision Measurement of the Lamb Shift in Muonium.

We report a new measurement of the n=2 Lamb shift in Muonium. Our result of 1047.2(2.3)_{stat}(1.1)_{syst} MHz comprises an order of magnitude improvement upon the previous best measurement. This value matches the theoretical calculation within 1 standard deviation allowing us to set limits on Lorentz and CPT violation in the muonic sector, as well as on new physics coupled to muons and electrons which could provide an explanation of the muon g-2 anomaly.

Intense beam of metastable Muonium.

Precision spectroscopy of the Muonium Lamb shift and fine structure requires a robust source of 2S Muonium. To date, the beam-foil technique is the only demonstrated method for creating such a beam in vacuum. Previous experiments using this technique were statistics limited, and new measurements would benefit tremendously from the efficient 2S production at a low energy muon ( < 20  keV) facility. Such a source of abundant low energy µ + has only become available in recent years, e.g. at the Low-Energy Muon beamline at the Paul Scherrer Institute. Using this source, we report on the successful creation of an intense, directed beam of metastable Muonium. We find that even though the theoretical Muonium fraction is maximal in the low energy range of 2-5 keV, scattering by the foil and transport characteristics of the beamline favor slightly higher µ + energies of 7-10 keV. We estimate that an event detection rate of a few events per second for a future Lamb shift measurement is feasible, enabling an increase in precision by two orders of magnitude over previous determinations.

Double hit reconstruction in large area multiplexed detectors.

A novel approach is presented to unfold particle hit positions in tracking detectors with multiplexed readout representing an underdetermined system of linear equations. The method does not use any prior information about the hit positions, and the only assumption in the procedure is that single strip charge values on consecutive detector strips follow a smooth distribution. Ambiguities introduced by charge sharing from multiplexing are reduced by using a regularization technique. We have tested this method on a multiplexed 50 × 50 cm2 Micromegas detector with 1037 strips and only 61 readout channels, using cosmic rays, and we have found that single and double clusters of hits can be reconstructed with high efficiency. In addition, simulations show that the algorithm is capable of reconstructing isolated hits in events with larger multiplicity.

Hemophagocytic lymphohistiocytosis: a serious challenge for every physician / Linfohistiocitosis hemofagocítica: un reto importante para los médicos

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Significantly increased CD70 up regulation on TEL-AML positive B cell precursor acute lymphoblastic leukemia cells following CD40 stimulation.

BACKGROUND: TEL-AML the most common genetic alteration in childhood precursor B acute lymphoblastic leukemia (BCP-ALL) is associated with a favorable prognosis. PATIENTS AND METHOD: We studied the expression of nerve growth factor/tumor necrosis factor receptor (NGFR/TNFR)/ligand family members on 108 primary BCP-ALL samples by flow cytometry and compared both their baseline expression and CD40-induced modulation on TEL-AML positive and negative leukemia samples. RESULTS: Our findings demonstrate that TEL-AML positive patients exhibit a significantly higher percentage of CD40, CD27 and p75NTR positive blasts at diagnosis. This might well contribute to the improved relapse-free survival of these patients assessed in Kaplan Meier analysis as CD27 and p75NTR directly mediate apoptotic signals. Furthermore CD40 ligation enhances antigen presenting and T cell stimulatory capacity via significant up regulation of CD70 while adequate response to physiological maturation signals as indicated by concomitant down regulation of CD27 is retained in TEL-AML positive leukemia. CONCLUSION: These data provide novel insights in immunological control mechanisms preserved in this leukemia subtype and suggest that not only treatment with chemicals such as HDAC inhibitors but also retained in vivo response to CD40 ligation contributes to improved immune surveillance in these patients which may add to a superior relapse-free survival observed particularly in the presence of other risk factors.

Fatal EBV infection and variable clinical manifestations in an XLP-1 pedigree - rapid diagnosis of primary immunodeficiencies may save lives.

Two related boys who died from fulminant infectious mononucleosis were diagnosed with X-linked lymphoproliferative disease type 1 (XLP-1). Family screening (n=17) identified 6 female mutation carriers and 2 more XLP-1 patients in whom, despite recurrent infections, agammaglobulinemia, and Hodgkin's Disease, the genetic basis had been unknown; demonstrating that awareness and early genetic testing are crucial to reveal underlying primary immunodeficiencies and improve outcome. Furthermore, XLP should be included routinely in the differential diagnosis of severe hypogammaglobulinemia and/or lymphoma in males.

Familial and acquired hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome in which an uncontrolled and ineffective immune response, triggered in most cases by infectious agents, leads to severe hyperinflammation. Familial forms of HLH (FHL), which are increasingly found also in adolescents and adults, are due to genetic defects leading to impaired function of natural killer cells and cytotoxic T cells. These mutations occur either in the perforin gene or in genes important for the exocytosis of cytotoxic granules. Cytotoxic granules contain perforin and granzymes, which induce apoptosis upon entering (infected) target cells. Additionally, perforin is important for the downregulation of the immune response. Acquired forms of HLH are encountered in association with (usually) viral infections, autoinflammatory/autoimmune diseases, malignant diseases, and acquired immune deficiency states (e.g., after organ transplantation). Treatment of HLH includes immune-suppressive and immune-modulatory agents, cytostatic drugs, and biological response modifiers. For patients with FHL, stem cell transplantation is indicated and can be curative.

Hemophagocytic lymphohistiocytosis: when the immune system runs amok.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome in which an exaggerated but ineffective immune response leads to severe hyperinflammation. Key players in HLH are activated lymphocytes and histiocytes which infiltrate all organs and secrete large amounts of cytokines. Cardinal symptoms are prolonged fever, hepatosplenomegaly, cytopenias, and hemophagocytosis. Biochemical markers include elevated ferritin, triglycerides, and low fibrinogen. HLH occurs on the basis of various inherited and acquired immune defects. Impaired function of natural killer cells and cytotoxic T cells is shared by all forms of HLH. Nearly all genetic defects identified in inherited cases of HLH are either mutations in the perforin gene or in genes important for the exocytosis of cytotoxic granules. Cytotoxic granules contain perforin and granzymes which induce apoptosis upon entering the target cell. Additionally perforin is important for the down-regulation of the immune response. Acquired forms of HLH are found in association with infectious agents, in patients with autoimmune diseases, in malignant diseases, and in patients receiving immune suppression or after organ transplantation. - HLH is still difficult to diagnose and may be overlooked since initially it may masquerade as a normal infection. HLH should be considered when symptoms are more pronounced than usual and in case of progression. Suppression of the severe hyperinflammation can be achieved with immunosuppressive and immunomodulatory agents and cytostatic drugs. Patients with genetic HLH have to undergo stem cell transplantation for cure.

Genotype-phenotype study of familial haemophagocytic lymphohistiocytosis due to perforin mutations.

BACKGROUND: PRF1 gene mutations are associated with familial haemophagocytic lymphohistiocytosis type 2 (FHL2). Genotype-phenotype analysis, previously hampered by limited numbers of patients, was for the first time performed by data pooling from five large centres worldwide. PATIENTS AND METHODS: Members of the Histiocyte Society were asked to report cases of FHL2 on specific forms. Data were pooled in a common database and analysed. RESULTS: The 124 patients had 63 different mutations (including 15 novel mutations): 11 nonsense, 10 frameshift, 38 missense and 4 in-frame deletions. Some mutations were found more commonly: 1122 G-->A (W374X), associated with Turkish origin, in 32 patients; 50delT (L17fsX22) associated with African/African American origin, in 21 patients; and 1090-91delCT (L364fsX), in 7 Japanese patients. Flow cytometry showed that perforin expression was absent in 40, reduced in 6 and normal in 4 patients. Patients presented at a median age of 3 months (quartiles: 2, 3 and 13 months), always with fever, splenomegaly and thrombocytopenia. NK activity was absent in 36 (51%), 5% in 4 (6%), "reduced" in 2 (3%) (not reported, n = 54). Nonsense mutations were significantly associated with younger age at onset (p<0.001) and absent natural killer activity (p = 0.008). CONCLUSION: PRF1 mutations are spread over the functional domains. Specific mutations are strongly associated with Turkish, African American and Japanese ethnic groups. Later onset and residual cytotoxic function are observed in patients with at least one missense mutation.

From neonates to adolescents--the diagnostic significance of pitted erythrocytes in hyposplenic and asplenic children.

BACKGROUND: Splenic function may be reduced or absent in a range of medical conditions in childhood, most prominently in homozygous sickle cell disease, celiac disease, or after total or partial splenectomy. In neonates and patients with malignant disease, transient hyposplenia has been reported as well. A simple method with reliable reference values is required to determine a patient's splenic function and thereby assess the risk of systemic infection. PATIENTS: Pitted erythrocytes (pitE) were determined semi-quantitatively in patients up to 20 years of age. This included splenectomized individuals, patients at risk for hyposplenia (homozygous sickle cell anemia (HbSS), leukemia, nephroblastoma and Hodgkin's disease after irradiation, patients after stem cell transplantation (SCT)), term and preterm neonates, and 90 controls (0-20 years of age, no neonates). METHOD: A capillary blood sample was diluted in buffered glutaraldehyde. PitE were scored using differential interference contrast microscopy with Nomarski optics. RESULTS: PitE were <2% in all controls regardless of age, in splenectomized individuals >18%. In patients with HbSS, pitE scores ranged from 6.2 to 44%. Scores did not exceed 2% in patients after SCT, irradiation, or during chemotherapy for leukaemia. In term neonates, pitE were increased in the perinatal period only. The elevation in preterm neonates persisted up to 2 months after birth. CONCLUSION: Serial measurement of pitE can be used to accurately and reliably assess splenic function in children. Except for neonates, pitE are consistently <2% in healthy individuals. For clinical purposes, the degree of hyposplenia can be determined to give an estimation of the risk of severe infection, e.g. in patients with HbSS or after partial splenectomy.

[SQUID-biosusceptometry in iron overloaded patients with hematologic diseases]. / SQUID-Biosuszeptometrie bei Eisenüberladungskrankheiten in der Hämatologie.

BACKGROUND: For the long-term survival of iron-loaded patients, early and well adjusted treatment with iron chelators is of crucial importance, especially in children. Basis of the adequate treatment are appropriate diagnostic parameters which are capable to monitor the range of the individual iron burden. PATIENTS: In the time period between 1989 and 2001, the status of iron loading was investigated in 1112 patients with post transfusion siderosis. METHODS: The iron concentration in liver and spleen was quantified by SQUID-biosusceptometry. Using these values, the whole body iron stores were calculated. RESULTS AND DISCUSSION: Based on a large number of patients with secondary siderosis, the benefit of SQUID-biosusceptometry for non-invasive liver iron quantification was evaluated retrospectively. In patients under treatment with deferoxamin, a new therapeutic DFO-index was defined which respects liver iron concentration instead of serum ferritin. This results in a more reliable information about DFO overdosing in a given patient.

Familial hemophagocytic lymphohistiocytosis: how late can the onset be?

BACKGROUND AND OBJECTIVES: Most patients with familial hemophagocytic lymphohistiocytosis (HLH) develop the disease within the first two years of age. In a minority of cases a later occurrence has been reported, with an upper age limit of eight years. A significant concordance of the age at onset within each family has also been observed. RESULTS: We report four cases of families with HLH diagnosed at an unusually late age, comprised between between 9 and 17 years; in each of these families another child developed the disease in infancy. The natural killer activity of the patients was depleted; nevertheless, we had indirect evidence that, in at least two families, mutations of the perforin gene were not causing the disease. INTERPRETATION AND CONCLUSIONS: Such a late onset is very unusual and suggests that there is a subgroup of families with HLH in which the disease may present early or late in different members. Thus in some families with HLH the siblings might remain at risk of developing the disease for several years. Their actual risk cannot be defined until the genetic mutation is identified in each family and assessed in each member.

Bone marrow transplantation in hemophagocytic lymphohistiocytosis.

Two important syndromes of hemophagocytic lymphohistiocytosis (HLH) have to be considered in infants and young children with recurrent fever, organomegaly and cytopenias. Familial hemophagocytic lymphohistiocytosis (FHLH) is a genetically heterogeneous autosomal recessive disease with histiocytic and lymphocytic infiltrations in multiple organs and is currently curable only by bone marrow transplantation (BMT). Secondary HLH most commonly results from viral infections and some patients may be cured by treating the causative organism, others will need chemotherapy and immunosuppression. Since infections can also trigger disease episodes in FHLH, making the correct diagnosis can prove difficult. The published experience of BMT in HLH is reviewed. Taken together, cure of the majority of patients with HLH by matched related BMT, unrelated or haploidentical BMT is possible. Incomplete resolution of disease activity does not necessarily impede a successful outcome. Central nervous system involvement will eventually develop in many HLH patients and may cause considerable morbidity. Appropriate early treatment and a timely BMT will hopefully decrease mortality rates and improve neurodevelopmental outcome in this disease.

Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis.

Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disease of early childhood characterized by nonmalignant accumulation and multivisceral infiltration of activated T lymphocytes and histiocytes (macrophages). Cytotoxic T and natural killer (NK) cell activity is markedly reduced or absent in these patients, and mutations in a lytic granule constituent, perforin, were recently identified in a number of FHL individuals. Here, we report a comprehensive survey of 34 additional patients with FHL for mutations in the coding region of the perforin gene and the relative frequency of perforin mutations in FHL. Perforin mutations were identified in 7 of the 34 families investigated. Six children were homozygous for the mutations, and one patient was a compound heterozygote. Four novel mutations were detected: one nonsense, two missense, and one deletion of one amino acid. In four families, a previously reported mutation at codon 374, causing a premature stop codon, was identified, and, therefore, this is the most common perforin mutation identified so far in FHL patients. We found perforin mutations in 20% of all FHL patients investigated (7/34), with a somewhat higher prevalence, approximately 30% (6/20), in children whose parents originated from Turkey. No other correlation between the type of mutation and the phenotype of the patients was evident from the present study. Our combined results from mutational analysis of 34 families and linkage analysis of a subset of consanguineous families indicate that perforin mutations account for 20%-40% of the FHL cases and the FHL 1 locus on chromosome 9 for approximately 10%, whereas the major part of the FHL cases are caused by mutations in not-yet-identified genes.